{"gene":"PIP","run_date":"2026-04-28T19:45:44","timeline":{"discoveries":[{"year":1994,"finding":"PIP (EP-GP/GCDFP-15/SABP) was shown to bind actin, fibrinogen, and bacteria (Streptococcus salivarius), and its molecular mass microheterogeneity was demonstrated to be predominantly caused by its carbohydrate moiety; ultrastructural localization to bacterial cell walls was shown by electron microscopy.","method":"Immunochemical and biochemical analysis, electron microscopy, binding assays with immobilized proteins","journal":"Biological chemistry Hoppe-Seyler","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, multiple binding partners identified by pulldown/binding assays, but no deep mechanistic follow-up","pmids":["7840903"],"is_preprint":false},{"year":1984,"finding":"GCDFP-15 (PIP) was localized ultrastructurally to Golgi vesicles and cytoplasmic granules in apocrine epithelium, and shown to be released by exocytosis at the cell apex, establishing its secretory mechanism.","method":"Low-temperature embedding colloidal gold immunoelectron microscopy","journal":"The American journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 — direct ultrastructural localization with defined secretory pathway, single lab","pmids":["6205595"],"is_preprint":false},{"year":1989,"finding":"Estradiol (E2) markedly decreased GCDFP-15 (PIP) mRNA levels and secretion in ZR-75-1 breast cancer cells, an effect reversed by antiestrogen LY156758; DHT and dexamethasone stimulated GCDFP-15 expression, establishing steroid hormone regulation of PIP gene expression.","method":"Northern blot/mRNA quantification, secretion assay, pharmacological inhibition with antiestrogen","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 — multiple hormonal manipulations with mRNA and protein secretion readouts, single lab","pmids":["2725533"],"is_preprint":false},{"year":2003,"finding":"GCDFP-15/PIP (gp17) was shown to function as an aspartyl proteinase capable of specifically cleaving fibronectin; differential N-linked glycosylation patterns were identified between pathological (breast disease) and physiological (seminal vesicle) forms of the protein, and the specific fibronectin-binding domain was mapped; the physiological form preferentially bound CD4 while both forms could interact with fibronectin.","method":"RP-HPLC, ProteinChip technology (SELDI-TOF), QStar MS/MS mass spectrometry, enzymatic digestion, protein-protein interaction assays","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal biochemical methods including mass spectrometry, binding domain mapping, and glycosylation characterization in single study","pmids":["12755619"],"is_preprint":false},{"year":1999,"finding":"Androgen receptor (AR)-mediated regulation of GCDFP-15 (PIP) expression was demonstrated: DHT stimulated GCDFP-15 mRNA expression and secretion in AR-positive breast cancer cell lines (MFM-223 and ZR-75-1), and this was blocked by pure antiandrogens hydroxyflutamide and casodex, establishing AR as a transcriptional regulator of PIP.","method":"mRNA expression assay, secretion assay, pharmacological competition with antiandrogens","journal":"International journal of molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 — receptor-mediated transcriptional regulation confirmed by competition experiments, single lab","pmids":["10402478"],"is_preprint":false},{"year":2013,"finding":"PIP silencing in T47D luminal A breast cancer cells reduced phosphorylation of focal adhesion kinase (FAK), EphB3, FYN, and HCK, and abolished serum-induced activation of AKT, ERK1/2, and JNK1, demonstrating that PIP supports RTK-dependent signaling; PIP depletion also impaired adhesion to fibronectin, cytoskeletal stress fiber assembly, and protein secretion.","method":"siRNA knockdown, RTK phosphorylation arrays (71 RTKs), western blot for downstream kinases, adhesion assay, microscopy","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — clean KD with multiple defined cellular phenotypes and pathway placement, single lab","pmids":["23755096"],"is_preprint":false},{"year":2018,"finding":"PIP is an aspartyl protease identified as required for proliferation and invasion of certain breast cancer cell types; PIP expression is regulated by androgen receptor and STAT5, and network analysis revealed PIP co-modulated genes associated with inhibition of proliferation, increased apoptosis, and enhanced cell adhesion.","method":"Gene expression profiling, network analysis, review of biochemical literature","journal":"American journal of cancer research","confidence":"Low","confidence_rationale":"Tier 3-4 — largely review/expression-based with limited direct mechanistic experimentation cited","pmids":["30555735"],"is_preprint":false},{"year":2021,"finding":"PIP interacts directly with aquaporin AQP5, with the interaction involving the AQP5 C-terminus and the N-terminal of PIP (one PIP molecule per AQP5 tetramer); PIP misexpression in PIP knockout mice and Sjögren's syndrome patients correlated with altered AQP5 distribution at the acinar apical membrane of salivary glands, establishing PIP as a regulator of AQP5 trafficking/localization.","method":"Co-immunoprecipitation, in vitro binding, mouse knockout model, immunofluorescence localization in human and mouse salivary gland tissue","journal":"Cells","confidence":"High","confidence_rationale":"Tier 2 — reciprocal interaction mapping with domain identification, knockout model with defined localization phenotype, replicated in human tissue","pmids":["34440877"],"is_preprint":false},{"year":2019,"finding":"Slug transcription factor was identified as a transcriptional regulator of PIP expression in macrophages in pulmonary hypertension secondary to pulmonary fibrosis; elevated PIP acted as an extracellular matrix protein that induced pulmonary arterial smooth muscle cell proliferation, and Slug inhibition decreased PH severity in a rat model.","method":"Immunohistochemistry, rat model of PF-PH, Slug inhibition experiment, cell proliferation assay","journal":"EMBO molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo model with defined Slug/PIP axis and functional consequence, single lab","pmids":["31468711"],"is_preprint":false},{"year":2009,"finding":"Bioinformatic and expression network analysis identified STAT5 as a potential transcriptional regulator of PIP, with PIP co-modulated genes associated with inhibition of proliferation, increased apoptosis, and enhanced cell adhesion in breast cancer cell lines.","method":"Microarray gene expression profiling, functional and regulatory network analysis using knowledge database","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 4 — primarily computational/expression-based; no direct experimental validation of STAT5-PIP transcriptional link","pmids":["19262752"],"is_preprint":false}],"current_model":"PIP (Prolactin-Inducible Protein/GCDFP-15) is a secreted aspartyl proteinase and glycoprotein that is transcriptionally regulated by androgen receptor (stimulated by DHT, inhibited by estrogen and antiandrogens) and potentially by STAT5 and Slug; it is released by exocytosis from Golgi-derived vesicles in apocrine cells, binds fibronectin (which it can cleave), actin, fibrinogen, CD4, and bacteria, interacts with AQP5 to regulate its apical membrane localization in salivary gland acinar cells, and supports RTK-dependent proliferative signaling (AKT, ERK1/2, JNK1) and cell adhesion to fibronectin in breast cancer cells."},"narrative":{"teleology":[{"year":1984,"claim":"Establishing that PIP is a secretory protein released via a defined exocytic pathway resolved how this glycoprotein reaches the extracellular space in apocrine tissues.","evidence":"Colloidal gold immunoelectron microscopy of apocrine epithelium localizing GCDFP-15 to Golgi vesicles and cytoplasmic granules with apical release","pmids":["6205595"],"confidence":"Medium","gaps":["Signals directing PIP to the secretory pathway not identified","Whether other cell types use the same exocytic route was not tested"]},{"year":1989,"claim":"Demonstrating that estradiol suppresses and DHT stimulates PIP mRNA and protein secretion established steroid hormone control of PIP expression and framed PIP as an androgen-responsive gene in breast cancer.","evidence":"Northern blot and secretion assays in ZR-75-1 breast cancer cells with estradiol, DHT, dexamethasone, and antiestrogen treatments","pmids":["2725533"],"confidence":"Medium","gaps":["Cis-regulatory elements mediating hormonal control not mapped","Whether AR directly binds the PIP promoter was not shown"]},{"year":1994,"claim":"Identifying actin, fibrinogen, and bacteria as PIP-binding partners, and attributing molecular mass heterogeneity to carbohydrate modifications, expanded PIP from a secretory marker to a multifunctional extracellular effector.","evidence":"Binding assays with immobilized proteins, electron microscopy localization to bacterial cell walls, biochemical deglycosylation","pmids":["7840903"],"confidence":"Medium","gaps":["Functional consequences of actin and fibrinogen binding not tested","Binding affinities not quantified"]},{"year":1999,"claim":"Confirming that AR mediates DHT-induced PIP expression using pure antiandrogens in multiple cell lines consolidated the androgen receptor as a direct transcriptional regulator of PIP.","evidence":"mRNA and secretion assays in MFM-223 and ZR-75-1 cells with DHT, hydroxyflutamide, and casodex","pmids":["10402478"],"confidence":"Medium","gaps":["Direct AR occupancy of PIP regulatory regions not demonstrated by ChIP","Contribution of AR co-regulators unknown"]},{"year":2003,"claim":"Identifying PIP as an aspartyl proteinase that cleaves fibronectin, and mapping its fibronectin-binding domain and differential glycosylation between pathological and physiological forms, established the enzymatic activity and substrate specificity of PIP.","evidence":"RP-HPLC, SELDI-TOF, QStar MS/MS mass spectrometry, enzymatic digestion assays, protein-protein interaction mapping","pmids":["12755619"],"confidence":"High","gaps":["Catalytic residues not mutagenized to confirm aspartyl protease mechanism","Other potential substrates not surveyed systematically"]},{"year":2013,"claim":"Showing that PIP depletion abolishes serum-induced AKT, ERK1/2, and JNK1 activation and reduces FAK and EphB3 phosphorylation placed PIP upstream of major RTK-dependent proliferative and adhesion signaling cascades in breast cancer cells.","evidence":"siRNA knockdown in T47D cells with RTK phosphorylation arrays, western blot, fibronectin adhesion and stress fiber assays","pmids":["23755096"],"confidence":"Medium","gaps":["Whether PIP acts via its protease activity or as a ligand/scaffold to promote RTK signaling is unresolved","Rescue with wild-type and protease-dead PIP not performed","Generalizability beyond T47D cells not tested"]},{"year":2019,"claim":"Identifying Slug as a transcriptional activator of PIP in macrophages, with secreted PIP driving pulmonary arterial smooth muscle cell proliferation, extended PIP's function beyond breast tissue into pulmonary vascular disease.","evidence":"Immunohistochemistry, rat model of pulmonary fibrosis-associated pulmonary hypertension, Slug inhibition reducing PH severity, smooth muscle cell proliferation assay","pmids":["31468711"],"confidence":"Medium","gaps":["Direct Slug binding to PIP promoter not shown","Receptor or mechanism by which extracellular PIP drives smooth muscle cell proliferation not identified"]},{"year":2021,"claim":"Demonstrating a direct PIP–AQP5 interaction with defined stoichiometry and showing that PIP loss disrupts AQP5 apical localization in salivary glands revealed PIP as a regulator of aquaporin trafficking with implications for Sjögren's syndrome.","evidence":"Co-immunoprecipitation, in vitro binding with domain mapping, PIP knockout mouse model, immunofluorescence in human and mouse salivary gland tissue","pmids":["34440877"],"confidence":"High","gaps":["Mechanism by which PIP maintains AQP5 at the apical membrane (retention vs. trafficking) not dissected","Whether this interaction is relevant in other AQP5-expressing tissues is unknown"]},{"year":null,"claim":"It remains unknown whether PIP's protease activity versus its scaffolding/binding properties drive its effects on RTK signaling and cell adhesion, and the catalytic mechanism has not been validated by active-site mutagenesis.","evidence":"","pmids":[],"confidence":"High","gaps":["No structure–function separation of protease versus binding activities","No crystal structure or active-site mutagenesis","Physiological substrates beyond fibronectin not systematically identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[3]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[3]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[1]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,1,3,8]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5]},{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[3,8]}],"complexes":[],"partners":["FN1","AQP5","CD4","ACTA1"],"other_free_text":[]},"mechanistic_narrative":"PIP (Prolactin-Inducible Protein/GCDFP-15) is a secreted aspartyl proteinase that functions in extracellular matrix remodeling, cell adhesion, and receptor tyrosine kinase signaling. Synthesized in Golgi-derived vesicles and released by apical exocytosis from apocrine epithelial cells [PMID:6205595], PIP binds and cleaves fibronectin, binds actin, fibrinogen, CD4, and bacteria, with differential glycosylation modulating its binding preferences [PMID:7840903, PMID:12755619]. PIP expression is stimulated by androgens via the androgen receptor and suppressed by estradiol, with Slug serving as an additional transcriptional activator in macrophages [PMID:2725533, PMID:10402478, PMID:31468711]. In breast cancer cells, PIP supports serum-induced activation of AKT, ERK1/2, and JNK1 downstream of focal adhesion kinase and EphB3 signaling, and in salivary gland acinar cells it directly interacts with aquaporin AQP5 to regulate its apical membrane localization [PMID:23755096, PMID:34440877]."},"prefetch_data":{"uniprot":{"accession":"P12273","full_name":"Prolactin-inducible protein","aliases":["Gross cystic disease fluid protein 15","GCDFP-15","Prolactin-induced protein","Secretory actin-binding protein","SABP","gp17"],"length_aa":146,"mass_kda":16.6,"function":"","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P12273/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PIP","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"PMVK","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PIP","total_profiled":1310},"omim":[{"mim_id":"620743","title":"SDE2 TELOMERE MAINTENANCE HOMOLOG; SDE2","url":"https://www.omim.org/entry/620743"},{"mim_id":"618288","title":"5-@HYDROXYMETHYLCYTOSINE-BINDING PROTEIN, EMBRYONIC STEM CELL-SPECIFIC; HMCES","url":"https://www.omim.org/entry/618288"},{"mim_id":"618175","title":"WARBURG-CINOTTI SYNDROME; WRCN","url":"https://www.omim.org/entry/618175"},{"mim_id":"616955","title":"RRAD- AND GEM-LIKE GTPase 2; REM2","url":"https://www.omim.org/entry/616955"},{"mim_id":"616086","title":"SprT-LIKE N-TERMINAL DOMAIN PROTEIN; SPRTN","url":"https://www.omim.org/entry/616086"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"salivary gland","ntpm":17175.0}],"url":"https://www.proteinatlas.org/search/PIP"},"hgnc":{"alias_symbol":["GCDFP-15","GCDFP15","GPIP4","SABP","BRST-2"],"prev_symbol":[]},"alphafold":{"accession":"P12273","domains":[{"cath_id":"2.60.40.10","chopping":"38-146","consensus_level":"high","plddt":96.946,"start":38,"end":146}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P12273","model_url":"https://alphafold.ebi.ac.uk/files/AF-P12273-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P12273-F1-predicted_aligned_error_v6.png","plddt_mean":89.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PIP","jax_strain_url":"https://www.jax.org/strain/search?query=PIP"},"sequence":{"accession":"P12273","fasta_url":"https://rest.uniprot.org/uniprotkb/P12273.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P12273/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P12273"}},"corpus_meta":[{"pmid":"11941371","id":"PMC_11941371","title":"The TRPM7 channel is inactivated by PIP(2) hydrolysis.","date":"2002","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/11941371","citation_count":428,"is_preprint":false},{"pmid":"17145637","id":"PMC_17145637","title":"Mammaglobin vs GCDFP-15: an immunohistologic validation survey for sensitivity and specificity.","date":"2007","source":"American journal of clinical pathology","url":"https://pubmed.ncbi.nlm.nih.gov/17145637","citation_count":166,"is_preprint":false},{"pmid":"10022840","id":"PMC_10022840","title":"Assembly requirements of PU.1-Pip (IRF-4) activator complexes: inhibiting function in vivo using fused dimers.","date":"1999","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/10022840","citation_count":160,"is_preprint":false},{"pmid":"19500308","id":"PMC_19500308","title":"Heat stress activates phospholipase D and triggers PIP accumulation at the plasma membrane and nucleus.","date":"2009","source":"The Plant journal : for cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/19500308","citation_count":158,"is_preprint":false},{"pmid":"18385163","id":"PMC_18385163","title":"Drought stress alters water relations and expression of PIP-type aquaporin genes in Nicotiana tabacum plants.","date":"2008","source":"Plant & cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/18385163","citation_count":131,"is_preprint":false},{"pmid":"19081076","id":"PMC_19081076","title":"Intrinsic negative cell cycle regulation provided by PIP box- and Cul4Cdt2-mediated destruction of E2f1 during S phase.","date":"2008","source":"Developmental cell","url":"https://pubmed.ncbi.nlm.nih.gov/19081076","citation_count":103,"is_preprint":false},{"pmid":"22197245","id":"PMC_22197245","title":"Cleavage furrow organization requires PIP(2)-mediated recruitment of anillin.","date":"2011","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/22197245","citation_count":100,"is_preprint":false},{"pmid":"30421640","id":"PMC_30421640","title":"Accurate delineation of cell cycle phase transitions in living cells with PIP-FUCCI.","date":"2018","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/30421640","citation_count":99,"is_preprint":false},{"pmid":"2459984","id":"PMC_2459984","title":"Immunohistochemistry of gross cystic disease fluid protein (GCDFP-15) in 65 benign sweat gland tumors of the skin.","date":"1988","source":"The American Journal of dermatopathology","url":"https://pubmed.ncbi.nlm.nih.gov/2459984","citation_count":98,"is_preprint":false},{"pmid":"17412762","id":"PMC_17412762","title":"Target-specific PIP(2) signalling: how might it work?","date":"2007","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/17412762","citation_count":97,"is_preprint":false},{"pmid":"2655863","id":"PMC_2655863","title":"Expression of GCDFP-15 in breast carcinomas. 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Markers Mammaglobin and GCDFP15 for Identifying Breast Cancer in Surgical and Cytology Specimens of Metastatic and Matched Primary Tumors.","date":"2016","source":"Applied immunohistochemistry & molecular morphology : AIMM","url":"https://pubmed.ncbi.nlm.nih.gov/25906123","citation_count":49,"is_preprint":false},{"pmid":"32558386","id":"PMC_32558386","title":"PI 3-kinase delta enhances axonal PIP3 to support axon regeneration in the adult CNS.","date":"2020","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32558386","citation_count":44,"is_preprint":false},{"pmid":"21900509","id":"PMC_21900509","title":"TRPM8 acute desensitization is mediated by calmodulin and requires PIP(2): distinction from tachyphylaxis.","date":"2011","source":"Journal of neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/21900509","citation_count":43,"is_preprint":false},{"pmid":"30628926","id":"PMC_30628926","title":"SOX10, GATA3, GCDFP15, Androgen Receptor, and Mammaglobin for the Differential Diagnosis Between Triple-negative Breast Cancer and TTF1-negative Lung Adenocarcinoma.","date":"2019","source":"The American journal of surgical pathology","url":"https://pubmed.ncbi.nlm.nih.gov/30628926","citation_count":43,"is_preprint":false},{"pmid":"7840903","id":"PMC_7840903","title":"Identity of human extra parotid glycoprotein (EP-GP) with secretory actin binding protein (SABP) and its biological properties.","date":"1994","source":"Biological chemistry Hoppe-Seyler","url":"https://pubmed.ncbi.nlm.nih.gov/7840903","citation_count":42,"is_preprint":false},{"pmid":"30555735","id":"PMC_30555735","title":"Prolactin-induced protein (PIP)-characterization and role in breast cancer progression.","date":"2018","source":"American journal of cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/30555735","citation_count":40,"is_preprint":false},{"pmid":"19233191","id":"PMC_19233191","title":"PKC activation and PIP(2) depletion underlie biphasic regulation of IKs by Gq-coupled receptors.","date":"2009","source":"Journal of molecular and cellular cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/19233191","citation_count":40,"is_preprint":false},{"pmid":"33637964","id":"PMC_33637964","title":"Specific PIP2 binding promotes calcium activation of TMEM16A chloride channels.","date":"2021","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/33637964","citation_count":39,"is_preprint":false},{"pmid":"30784597","id":"PMC_30784597","title":"ORP4L Extracts and Presents PIP2 from Plasma Membrane for PLCβ3 Catalysis: Targeting It Eradicates Leukemia Stem Cells.","date":"2019","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/30784597","citation_count":39,"is_preprint":false},{"pmid":"35079141","id":"PMC_35079141","title":"PIP2 determines length and stability of primary cilia by balancing membrane turnovers.","date":"2022","source":"Communications 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salicylic acid to heat acclimation-induced thermotolerance in pea leaves.","date":"2005","source":"Journal of plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/16455354","citation_count":35,"is_preprint":false},{"pmid":"30244966","id":"PMC_30244966","title":"Structural Basis of TRPV4 N Terminus Interaction with Syndapin/PACSIN1-3 and PIP2.","date":"2018","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/30244966","citation_count":34,"is_preprint":false},{"pmid":"12755619","id":"PMC_12755619","title":"Structural study of GCDFP-15/gp17 in disease versus physiological conditions using a proteomic approach.","date":"2003","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12755619","citation_count":34,"is_preprint":false},{"pmid":"8693878","id":"PMC_8693878","title":"Value of GCDFP-15 (BRST-2) as a specific immunocytochemical marker for breast carcinoma in cytologic specimens.","date":"1996","source":"Acta cytologica","url":"https://pubmed.ncbi.nlm.nih.gov/8693878","citation_count":34,"is_preprint":false},{"pmid":"19262752","id":"PMC_19262752","title":"A functional and regulatory network associated with PIP expression in human breast cancer.","date":"2009","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/19262752","citation_count":33,"is_preprint":false},{"pmid":"23755096","id":"PMC_23755096","title":"Prolactin-induced protein (PIP) regulates proliferation of luminal A type breast cancer cells in an estrogen-independent manner.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23755096","citation_count":33,"is_preprint":false},{"pmid":"28720589","id":"PMC_28720589","title":"Dynamic role of the tether helix in PIP2-dependent gating of a G protein-gated potassium channel.","date":"2017","source":"The Journal of general 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Evidence for a Reduced Transpiration Rate and Expression of Major PIP Aquaporin Genes.","date":"2018","source":"Plant & cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/29415257","citation_count":32,"is_preprint":false},{"pmid":"27028641","id":"PMC_27028641","title":"PIP Water Transport and Its pH Dependence Are Regulated by Tetramer Stoichiometry.","date":"2016","source":"Biophysical journal","url":"https://pubmed.ncbi.nlm.nih.gov/27028641","citation_count":31,"is_preprint":false},{"pmid":"19620839","id":"PMC_19620839","title":"GCDFP-15 positive and TTF-1 negative primary lung neoplasms: a tissue microarray study of 381 primary lung tumors.","date":"2009","source":"Applied immunohistochemistry & molecular morphology : AIMM","url":"https://pubmed.ncbi.nlm.nih.gov/19620839","citation_count":28,"is_preprint":false},{"pmid":"19217055","id":"PMC_19217055","title":"Diagnostic utility of mammaglobin and GCDFP-15 in the identification of metastatic breast carcinoma in fluid specimens.","date":"2009","source":"Diagnostic cytopathology","url":"https://pubmed.ncbi.nlm.nih.gov/19217055","citation_count":28,"is_preprint":false},{"pmid":"18330597","id":"PMC_18330597","title":"Barley plasma membrane intrinsic proteins (PIP Aquaporins) as water and CO2 transporters.","date":"2008","source":"Pflugers Archiv : European journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/18330597","citation_count":28,"is_preprint":false},{"pmid":"16563698","id":"PMC_16563698","title":"Regulation of type II PIP kinase by PKD phosphorylation.","date":"2006","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/16563698","citation_count":28,"is_preprint":false},{"pmid":"15182429","id":"PMC_15182429","title":"Expression of the prolactin-inducible protein (PIP/GCDFP15) gene in benign epithelium and adenocarcinoma of the prostate.","date":"2004","source":"Cancer science","url":"https://pubmed.ncbi.nlm.nih.gov/15182429","citation_count":27,"is_preprint":false},{"pmid":"28715108","id":"PMC_28715108","title":"Ivermectin activates GIRK channels in a PIP2 -dependent, Gβγ -independent manner and an amino acid residue at the slide helix governs the activation.","date":"2017","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/28715108","citation_count":27,"is_preprint":false},{"pmid":"22950482","id":"PMC_22950482","title":"Phosphatidylinositol 4,5-biphosphate (PIP(2)) lipids regulate the phosphorylation of syntaxin N-terminus by modulating both its position and local structure.","date":"2012","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22950482","citation_count":27,"is_preprint":false},{"pmid":"32992595","id":"PMC_32992595","title":"A Survey of Barley PIP Aquaporin Ionic Conductance Reveals Ca2+-Sensitive HvPIP2;8 Na+ and K+ Conductance.","date":"2020","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/32992595","citation_count":26,"is_preprint":false},{"pmid":"17584838","id":"PMC_17584838","title":"Decrease in PIP(2) channel interactions is the final common mechanism involved in PKC- and arachidonic acid-mediated inhibitions of GABA(B)-activated K+ current.","date":"2007","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/17584838","citation_count":26,"is_preprint":false},{"pmid":"22403073","id":"PMC_22403073","title":"PIP kinases from the cell membrane to the nucleus.","date":"2012","source":"Sub-cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22403073","citation_count":24,"is_preprint":false},{"pmid":"6205595","id":"PMC_6205595","title":"The ultrastructural localization of gross cystic disease fluid protein (GCDFP-15) in breast epithelium.","date":"1984","source":"The American journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/6205595","citation_count":24,"is_preprint":false},{"pmid":"20045432","id":"PMC_20045432","title":"Venom neutralization by purified bioactive molecules: Synthetic peptide derivatives of the endogenous PLA(2) inhibitory protein PIP (a mini-review).","date":"2010","source":"Toxicon : official journal of the International Society on Toxinology","url":"https://pubmed.ncbi.nlm.nih.gov/20045432","citation_count":24,"is_preprint":false},{"pmid":"34440877","id":"PMC_34440877","title":"Unraveling Human AQP5-PIP Molecular Interaction and Effect on AQP5 Salivary Glands Localization in SS Patients.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/34440877","citation_count":24,"is_preprint":false},{"pmid":"32499698","id":"PMC_32499698","title":"Andersen-Tawil Syndrome Is Associated With Impaired PIP2 Regulation of the Potassium Channel Kir2.1.","date":"2020","source":"Frontiers in pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/32499698","citation_count":24,"is_preprint":false},{"pmid":"32434869","id":"PMC_32434869","title":"Bidirectional transfer of homeoprotein EN2 across the plasma membrane requires PIP2.","date":"2020","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/32434869","citation_count":23,"is_preprint":false},{"pmid":"35646908","id":"PMC_35646908","title":"When PIP2 Meets p53: Nuclear Phosphoinositide Signaling in the DNA Damage Response.","date":"2022","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/35646908","citation_count":22,"is_preprint":false},{"pmid":"31468711","id":"PMC_31468711","title":"Histological hallmarks and role of Slug/PIP axis in pulmonary hypertension secondary to pulmonary fibrosis.","date":"2019","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/31468711","citation_count":22,"is_preprint":false},{"pmid":"25252779","id":"PMC_25252779","title":"PIP-DB: the Protein Isoelectric Point database.","date":"2014","source":"Bioinformatics (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/25252779","citation_count":20,"is_preprint":false},{"pmid":"21493688","id":"PMC_21493688","title":"Cdt1 proteolysis is promoted by dual PIP degrons and is modulated by PCNA ubiquitylation.","date":"2011","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/21493688","citation_count":20,"is_preprint":false},{"pmid":"31898884","id":"PMC_31898884","title":"Metallointercalator [Ru(dppz)2(PIP)]2+ Renders BRCA Wild-Type Triple-Negative Breast Cancer Cells Hypersensitive to PARP Inhibition.","date":"2020","source":"ACS chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/31898884","citation_count":19,"is_preprint":false},{"pmid":"19331818","id":"PMC_19331818","title":"Contribution of PIP-5 kinase Ialpha to raft-based FcgammaRIIA signaling.","date":"2009","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/19331818","citation_count":19,"is_preprint":false},{"pmid":"31900312","id":"PMC_31900312","title":"Discovery of Small Molecules That Target the Phosphatidylinositol (3,4,5) Trisphosphate (PIP3)-Dependent Rac Exchanger 1 (P-Rex1) PIP3-Binding Site and Inhibit P-Rex1-Dependent Functions in Neutrophils.","date":"2020","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/31900312","citation_count":19,"is_preprint":false},{"pmid":"27723083","id":"PMC_27723083","title":"Protein Interaction Profile Sequencing (PIP-seq).","date":"2016","source":"Current protocols in molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/27723083","citation_count":18,"is_preprint":false},{"pmid":"36396757","id":"PMC_36396757","title":"Phosphatidylinositol 4,5-bisphosphate (PIP2) facilitates norepinephrine transporter dimerization and modulates substrate efflux.","date":"2022","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/36396757","citation_count":18,"is_preprint":false},{"pmid":"29150438","id":"PMC_29150438","title":"A PIP2-derived amplification loop fuels the sustained initiation of B cell activation.","date":"2017","source":"Science immunology","url":"https://pubmed.ncbi.nlm.nih.gov/29150438","citation_count":18,"is_preprint":false},{"pmid":"35020418","id":"PMC_35020418","title":"Nir1 constitutively localizes at ER-PM junctions and promotes Nir2 recruitment for PIP2 homeostasis.","date":"2022","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/35020418","citation_count":18,"is_preprint":false},{"pmid":"37788993","id":"PMC_37788993","title":"Structural insights into the conformational changes of BTR1/SLC4A11 in complex with PIP2.","date":"2023","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/37788993","citation_count":18,"is_preprint":false},{"pmid":"30902142","id":"PMC_30902142","title":"Prolactin and Prolactin-inducible protein (PIP) in the pathogenesis of primary acquired nasolacrimal duct obstruction (PANDO).","date":"2019","source":"Medical hypotheses","url":"https://pubmed.ncbi.nlm.nih.gov/30902142","citation_count":18,"is_preprint":false},{"pmid":"33984330","id":"PMC_33984330","title":"Unlocking the PIP-box: A peptide library reveals interactions that drive high-affinity binding to human PCNA.","date":"2021","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33984330","citation_count":18,"is_preprint":false},{"pmid":"3279111","id":"PMC_3279111","title":"Immunoperoxidase localization of GCDFP-15 with mouse monoclonal antibodies versus rabbit antiserum.","date":"1988","source":"The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society","url":"https://pubmed.ncbi.nlm.nih.gov/3279111","citation_count":17,"is_preprint":false},{"pmid":"28842595","id":"PMC_28842595","title":"Regulation of HGF-induced hepatocyte proliferation by the small GTPase Arf6 through the PIP2-producing enzyme PIP5K1A.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28842595","citation_count":17,"is_preprint":false},{"pmid":"29393635","id":"PMC_29393635","title":"Pip-HoGu: An Artificial Assembly with Cooperative DNA Recognition Capable of Mimicking Transcription Factor Pairs.","date":"2018","source":"Journal of the American Chemical Society","url":"https://pubmed.ncbi.nlm.nih.gov/29393635","citation_count":16,"is_preprint":false},{"pmid":"29317494","id":"PMC_29317494","title":"Hydrogen sulfide inhibits Kir2 and Kir3 channels by decreasing sensitivity to the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2).","date":"2018","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/29317494","citation_count":16,"is_preprint":false},{"pmid":"36633397","id":"PMC_36633397","title":"Inhibition of the proton-activated chloride channel PAC by PIP2.","date":"2023","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/36633397","citation_count":15,"is_preprint":false},{"pmid":"22369174","id":"PMC_22369174","title":"Can we see PIP(3) and hydrogen peroxide with a single probe?","date":"2012","source":"Antioxidants & redox signaling","url":"https://pubmed.ncbi.nlm.nih.gov/22369174","citation_count":15,"is_preprint":false},{"pmid":"37972760","id":"PMC_37972760","title":"Deciphering the effect of salinity and boron stress on broccoli plants reveals that membranes phytosterols and PIP aquaporins facilitate stress adaptation.","date":"2023","source":"Plant science : an international journal of experimental plant biology","url":"https://pubmed.ncbi.nlm.nih.gov/37972760","citation_count":15,"is_preprint":false},{"pmid":"10402478","id":"PMC_10402478","title":"Regulation of GCDFP-15 expression in human mammary cancer cells.","date":"1999","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/10402478","citation_count":14,"is_preprint":false},{"pmid":"29656222","id":"PMC_29656222","title":"Prolactin Induced Protein (PIP) is a potential biomarker for early stage and malignant breast cancer.","date":"2018","source":"Breast (Edinburgh, Scotland)","url":"https://pubmed.ncbi.nlm.nih.gov/29656222","citation_count":14,"is_preprint":false},{"pmid":"36047384","id":"PMC_36047384","title":"The dynamic interplay of PIP2 and ATP in the regulation of the KATP channel.","date":"2022","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/36047384","citation_count":13,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":46388,"output_tokens":2486,"usd":0.088227},"stage2":{"model":"claude-opus-4-6","input_tokens":5665,"output_tokens":2168,"usd":0.123787},"total_usd":0.212014,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"Looking at these abstracts, I need to identify which ones are about the human/mammalian gene \"PIP\" (Prolactin-Inducible Protein / GCDFP-15) versus other uses of \"PIP\" (phosphatidylinositol phosphate lipids, plant aquaporins, PCNA-interacting protein boxes, etc.).\n\nThe human gene PIP encodes Prolactin-Inducible Protein (also known as GCDFP-15, gp17, SABP). Let me extract mechanistic findings specifically about this protein.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"PIP (EP-GP/GCDFP-15/SABP) was shown to bind actin, fibrinogen, and bacteria (Streptococcus salivarius), and its molecular mass microheterogeneity was demonstrated to be predominantly caused by its carbohydrate moiety; ultrastructural localization to bacterial cell walls was shown by electron microscopy.\",\n      \"method\": \"Immunochemical and biochemical analysis, electron microscopy, binding assays with immobilized proteins\",\n      \"journal\": \"Biological chemistry Hoppe-Seyler\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, multiple binding partners identified by pulldown/binding assays, but no deep mechanistic follow-up\",\n      \"pmids\": [\"7840903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1984,\n      \"finding\": \"GCDFP-15 (PIP) was localized ultrastructurally to Golgi vesicles and cytoplasmic granules in apocrine epithelium, and shown to be released by exocytosis at the cell apex, establishing its secretory mechanism.\",\n      \"method\": \"Low-temperature embedding colloidal gold immunoelectron microscopy\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct ultrastructural localization with defined secretory pathway, single lab\",\n      \"pmids\": [\"6205595\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"Estradiol (E2) markedly decreased GCDFP-15 (PIP) mRNA levels and secretion in ZR-75-1 breast cancer cells, an effect reversed by antiestrogen LY156758; DHT and dexamethasone stimulated GCDFP-15 expression, establishing steroid hormone regulation of PIP gene expression.\",\n      \"method\": \"Northern blot/mRNA quantification, secretion assay, pharmacological inhibition with antiestrogen\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple hormonal manipulations with mRNA and protein secretion readouts, single lab\",\n      \"pmids\": [\"2725533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"GCDFP-15/PIP (gp17) was shown to function as an aspartyl proteinase capable of specifically cleaving fibronectin; differential N-linked glycosylation patterns were identified between pathological (breast disease) and physiological (seminal vesicle) forms of the protein, and the specific fibronectin-binding domain was mapped; the physiological form preferentially bound CD4 while both forms could interact with fibronectin.\",\n      \"method\": \"RP-HPLC, ProteinChip technology (SELDI-TOF), QStar MS/MS mass spectrometry, enzymatic digestion, protein-protein interaction assays\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal biochemical methods including mass spectrometry, binding domain mapping, and glycosylation characterization in single study\",\n      \"pmids\": [\"12755619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Androgen receptor (AR)-mediated regulation of GCDFP-15 (PIP) expression was demonstrated: DHT stimulated GCDFP-15 mRNA expression and secretion in AR-positive breast cancer cell lines (MFM-223 and ZR-75-1), and this was blocked by pure antiandrogens hydroxyflutamide and casodex, establishing AR as a transcriptional regulator of PIP.\",\n      \"method\": \"mRNA expression assay, secretion assay, pharmacological competition with antiandrogens\",\n      \"journal\": \"International journal of molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — receptor-mediated transcriptional regulation confirmed by competition experiments, single lab\",\n      \"pmids\": [\"10402478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PIP silencing in T47D luminal A breast cancer cells reduced phosphorylation of focal adhesion kinase (FAK), EphB3, FYN, and HCK, and abolished serum-induced activation of AKT, ERK1/2, and JNK1, demonstrating that PIP supports RTK-dependent signaling; PIP depletion also impaired adhesion to fibronectin, cytoskeletal stress fiber assembly, and protein secretion.\",\n      \"method\": \"siRNA knockdown, RTK phosphorylation arrays (71 RTKs), western blot for downstream kinases, adhesion assay, microscopy\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with multiple defined cellular phenotypes and pathway placement, single lab\",\n      \"pmids\": [\"23755096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PIP is an aspartyl protease identified as required for proliferation and invasion of certain breast cancer cell types; PIP expression is regulated by androgen receptor and STAT5, and network analysis revealed PIP co-modulated genes associated with inhibition of proliferation, increased apoptosis, and enhanced cell adhesion.\",\n      \"method\": \"Gene expression profiling, network analysis, review of biochemical literature\",\n      \"journal\": \"American journal of cancer research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3-4 — largely review/expression-based with limited direct mechanistic experimentation cited\",\n      \"pmids\": [\"30555735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PIP interacts directly with aquaporin AQP5, with the interaction involving the AQP5 C-terminus and the N-terminal of PIP (one PIP molecule per AQP5 tetramer); PIP misexpression in PIP knockout mice and Sjögren's syndrome patients correlated with altered AQP5 distribution at the acinar apical membrane of salivary glands, establishing PIP as a regulator of AQP5 trafficking/localization.\",\n      \"method\": \"Co-immunoprecipitation, in vitro binding, mouse knockout model, immunofluorescence localization in human and mouse salivary gland tissue\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal interaction mapping with domain identification, knockout model with defined localization phenotype, replicated in human tissue\",\n      \"pmids\": [\"34440877\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Slug transcription factor was identified as a transcriptional regulator of PIP expression in macrophages in pulmonary hypertension secondary to pulmonary fibrosis; elevated PIP acted as an extracellular matrix protein that induced pulmonary arterial smooth muscle cell proliferation, and Slug inhibition decreased PH severity in a rat model.\",\n      \"method\": \"Immunohistochemistry, rat model of PF-PH, Slug inhibition experiment, cell proliferation assay\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo model with defined Slug/PIP axis and functional consequence, single lab\",\n      \"pmids\": [\"31468711\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Bioinformatic and expression network analysis identified STAT5 as a potential transcriptional regulator of PIP, with PIP co-modulated genes associated with inhibition of proliferation, increased apoptosis, and enhanced cell adhesion in breast cancer cell lines.\",\n      \"method\": \"Microarray gene expression profiling, functional and regulatory network analysis using knowledge database\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — primarily computational/expression-based; no direct experimental validation of STAT5-PIP transcriptional link\",\n      \"pmids\": [\"19262752\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PIP (Prolactin-Inducible Protein/GCDFP-15) is a secreted aspartyl proteinase and glycoprotein that is transcriptionally regulated by androgen receptor (stimulated by DHT, inhibited by estrogen and antiandrogens) and potentially by STAT5 and Slug; it is released by exocytosis from Golgi-derived vesicles in apocrine cells, binds fibronectin (which it can cleave), actin, fibrinogen, CD4, and bacteria, interacts with AQP5 to regulate its apical membrane localization in salivary gland acinar cells, and supports RTK-dependent proliferative signaling (AKT, ERK1/2, JNK1) and cell adhesion to fibronectin in breast cancer cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PIP (Prolactin-Inducible Protein/GCDFP-15) is a secreted aspartyl proteinase that functions in extracellular matrix remodeling, cell adhesion, and receptor tyrosine kinase signaling. Synthesized in Golgi-derived vesicles and released by apical exocytosis from apocrine epithelial cells [PMID:6205595], PIP binds and cleaves fibronectin, binds actin, fibrinogen, CD4, and bacteria, with differential glycosylation modulating its binding preferences [PMID:7840903, PMID:12755619]. PIP expression is stimulated by androgens via the androgen receptor and suppressed by estradiol, with Slug serving as an additional transcriptional activator in macrophages [PMID:2725533, PMID:10402478, PMID:31468711]. In breast cancer cells, PIP supports serum-induced activation of AKT, ERK1/2, and JNK1 downstream of focal adhesion kinase and EphB3 signaling, and in salivary gland acinar cells it directly interacts with aquaporin AQP5 to regulate its apical membrane localization [PMID:23755096, PMID:34440877].\",\n  \"teleology\": [\n    {\n      \"year\": 1984,\n      \"claim\": \"Establishing that PIP is a secretory protein released via a defined exocytic pathway resolved how this glycoprotein reaches the extracellular space in apocrine tissues.\",\n      \"evidence\": \"Colloidal gold immunoelectron microscopy of apocrine epithelium localizing GCDFP-15 to Golgi vesicles and cytoplasmic granules with apical release\",\n      \"pmids\": [\"6205595\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signals directing PIP to the secretory pathway not identified\", \"Whether other cell types use the same exocytic route was not tested\"]\n    },\n    {\n      \"year\": 1989,\n      \"claim\": \"Demonstrating that estradiol suppresses and DHT stimulates PIP mRNA and protein secretion established steroid hormone control of PIP expression and framed PIP as an androgen-responsive gene in breast cancer.\",\n      \"evidence\": \"Northern blot and secretion assays in ZR-75-1 breast cancer cells with estradiol, DHT, dexamethasone, and antiestrogen treatments\",\n      \"pmids\": [\"2725533\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cis-regulatory elements mediating hormonal control not mapped\", \"Whether AR directly binds the PIP promoter was not shown\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Identifying actin, fibrinogen, and bacteria as PIP-binding partners, and attributing molecular mass heterogeneity to carbohydrate modifications, expanded PIP from a secretory marker to a multifunctional extracellular effector.\",\n      \"evidence\": \"Binding assays with immobilized proteins, electron microscopy localization to bacterial cell walls, biochemical deglycosylation\",\n      \"pmids\": [\"7840903\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequences of actin and fibrinogen binding not tested\", \"Binding affinities not quantified\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Confirming that AR mediates DHT-induced PIP expression using pure antiandrogens in multiple cell lines consolidated the androgen receptor as a direct transcriptional regulator of PIP.\",\n      \"evidence\": \"mRNA and secretion assays in MFM-223 and ZR-75-1 cells with DHT, hydroxyflutamide, and casodex\",\n      \"pmids\": [\"10402478\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct AR occupancy of PIP regulatory regions not demonstrated by ChIP\", \"Contribution of AR co-regulators unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identifying PIP as an aspartyl proteinase that cleaves fibronectin, and mapping its fibronectin-binding domain and differential glycosylation between pathological and physiological forms, established the enzymatic activity and substrate specificity of PIP.\",\n      \"evidence\": \"RP-HPLC, SELDI-TOF, QStar MS/MS mass spectrometry, enzymatic digestion assays, protein-protein interaction mapping\",\n      \"pmids\": [\"12755619\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic residues not mutagenized to confirm aspartyl protease mechanism\", \"Other potential substrates not surveyed systematically\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showing that PIP depletion abolishes serum-induced AKT, ERK1/2, and JNK1 activation and reduces FAK and EphB3 phosphorylation placed PIP upstream of major RTK-dependent proliferative and adhesion signaling cascades in breast cancer cells.\",\n      \"evidence\": \"siRNA knockdown in T47D cells with RTK phosphorylation arrays, western blot, fibronectin adhesion and stress fiber assays\",\n      \"pmids\": [\"23755096\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PIP acts via its protease activity or as a ligand/scaffold to promote RTK signaling is unresolved\", \"Rescue with wild-type and protease-dead PIP not performed\", \"Generalizability beyond T47D cells not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identifying Slug as a transcriptional activator of PIP in macrophages, with secreted PIP driving pulmonary arterial smooth muscle cell proliferation, extended PIP's function beyond breast tissue into pulmonary vascular disease.\",\n      \"evidence\": \"Immunohistochemistry, rat model of pulmonary fibrosis-associated pulmonary hypertension, Slug inhibition reducing PH severity, smooth muscle cell proliferation assay\",\n      \"pmids\": [\"31468711\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct Slug binding to PIP promoter not shown\", \"Receptor or mechanism by which extracellular PIP drives smooth muscle cell proliferation not identified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrating a direct PIP–AQP5 interaction with defined stoichiometry and showing that PIP loss disrupts AQP5 apical localization in salivary glands revealed PIP as a regulator of aquaporin trafficking with implications for Sjögren's syndrome.\",\n      \"evidence\": \"Co-immunoprecipitation, in vitro binding with domain mapping, PIP knockout mouse model, immunofluorescence in human and mouse salivary gland tissue\",\n      \"pmids\": [\"34440877\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PIP maintains AQP5 at the apical membrane (retention vs. trafficking) not dissected\", \"Whether this interaction is relevant in other AQP5-expressing tissues is unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown whether PIP's protease activity versus its scaffolding/binding properties drive its effects on RTK signaling and cell adhesion, and the catalytic mechanism has not been validated by active-site mutagenesis.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure–function separation of protease versus binding activities\", \"No crystal structure or active-site mutagenesis\", \"Physiological substrates beyond fibronectin not systematically identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 1, 3, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [3, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"FN1\", \"AQP5\", \"CD4\", \"ACTA1\"],\n    \"other_free_text\": []\n  }\n}\n```"}