Affinage

FARP1

FERM, ARHGEF and pleckstrin domain-containing protein 1 · UniProt Q9Y4F1

Length
1045 aa
Mass
118.6 kDa
Annotated
2026-04-28
21 papers in source corpus 12 papers cited in narrative 12 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

FARP1 is a FERM–DH–PH domain-containing Rho guanine nucleotide exchange factor that couples transmembrane receptor signals to Rac1 and Cdc42 activation, driving F-actin remodeling in processes including synaptogenesis, dendritic arborization, cell migration, tunneling nanotube formation, and glucose transporter translocation. Its FERM domain binds phospholipids via a conserved positively charged surface patch and directly engages transmembrane partners—SynCAM 1 at postsynaptic sites, PlexinA1/PlexinA4 in Semaphorin signaling, and GPR81 in skeletal muscle—to recruit FARP1 to the plasma membrane where the DH domain catalyzes GTP loading of Rac1 and Cdc42 (PMID:29992992, PMID:23209303, PMID:19217374, PMID:41530347). FARP1 operates downstream of diverse upstream inputs including retinoid-induced transcription, PI3K/PKCα signaling from Gi/o-coupled GPCRs, EGFR/c-Met receptor tyrosine kinases, and Scribble-dependent polarity complexes, and is directly phosphorylated by MAP4K4 (PMID:37390986, PMID:34731623, PMID:36347240, PMID:26422651). In neurons, FARP1 functions as an essential effector linking Semaphorin6A/PlexinA4 and Sema3A/Neuropilin-1/PlexinA1 signaling to dendritic growth and synapse formation, while in non-neuronal cells it drives Rac1-dependent migration ruffles, Cdc42-dependent tunneling nanotubes, and GPR81-mediated insulin-independent GLUT4 translocation (PMID:19217374, PMID:24899721, PMID:34731623, PMID:41530347).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 1997 Medium

    Cloning of FARP1 (CDEP) established its multi-domain architecture (FERM–DH–PH), predicting it as a Rho-family GEF linked to cytoskeletal regulation—answering the basic question of gene identity and domain composition.

    Evidence cDNA cloning, sequence analysis, and Northern blot from human tissues

    PMID:9425278

    Open questions at the time
    • GEF activity was inferred from sequence homology, not biochemically demonstrated
    • substrate GTPase specificity unknown
  2. 2001 High

    Biochemical demonstration that the FARP1 DH-PH domain catalyzes GDP dissociation from RhoA in vitro confirmed it is a bona fide Rho-GEF, and its truncated form's transforming activity in fibroblasts linked GEF activity to a cellular outcome.

    Evidence In vitro [³H]GDP dissociation assay with recombinant DH-PH domain; NIH3T3 focus formation assay

    PMID:11680691

    Open questions at the time
    • Initial assay used RhoA as substrate; later studies showed primary activity toward Rac1/Cdc42, raising questions about in vivo substrate preference
    • mechanism of autoinhibition by FERM domain not addressed
  3. 2009 High

    Placing FARP1 as an effector of Semaphorin6A/PlexinA4 signaling in motor neuron dendritic growth established the first physiological receptor-to-GEF pathway for FARP1, showing its GEF domain is required for dendritic morphogenesis and that retinoid signaling induces FARP1 expression.

    Evidence Loss- and gain-of-function in chick spinal cord; GEF-domain deletion mutants; epistasis with Sema6A/PlexA4

    PMID:19217374

    Open questions at the time
    • Whether FARP1 activates Rac1 or Cdc42 in this context was not resolved
    • direct physical interaction between FARP1 and PlexinA4 not demonstrated
  4. 2012 High

    Identification of SynCAM 1 as a direct FERM-domain binding partner at the postsynapse, combined with mutual epistasis and Rac1 activation assays, established FARP1 as a synaptic organizer linking adhesion to actin-based spine remodeling and synapse number regulation.

    Evidence Proteomics of SynCAM 1 KO synaptic membranes; reciprocal Co-IP; Rac1 activity assay; spine/synapse morphology in knockdown/overexpression; F-actin staining

    PMID:23209303

    Open questions at the time
    • Structural basis of FERM–SynCAM 1 interaction unresolved
    • retrograde signaling mechanism not molecularly defined
  5. 2014 High

    Demonstrating that FARP1 interacts with Neuropilin-1/PlexinA1 and is required for Sema3A-induced dendritic arborization broadened the repertoire of Semaphorin pathways utilizing FARP1, and revealed that neuronal activity gates this response by stabilizing PlexinA1.

    Evidence Co-IP of FARP1–Neuropilin-1/PlexinA1; FARP1 knockdown with dendritic morphology readout; activity-dependent PlexinA1 stabilization via proteasome inhibition

    PMID:24899721

    Open questions at the time
    • Whether FARP1 binds PlexinA1 directly or via Neuropilin-1 scaffolding not distinguished
    • GTPase substrate specificity in this pathway not tested
  6. 2015 High

    Identifying MAP4K4 as a kinase that directly phosphorylates FARP1 at a pTL motif provided the first post-translational regulatory mechanism for FARP1 and connected it to a broader kinase-GEF signaling axis in neurite outgrowth.

    Evidence Phosphoproteomics; in vitro kinase assay with recombinant MAP4K4 and FARP1; Co-IP; neurite outgrowth assay with MAP4K4 inhibitor

    PMID:26422651

    Open questions at the time
    • Functional consequence of phosphorylation on GEF activity not directly measured
    • phosphorylation site mutant phenotype not tested in neurons
  7. 2016 Medium

    Showing that FARP1 knockdown reduces Cdc42 activity in PC12 cells established Cdc42 as a second in vivo substrate, broadening FARP1's GTPase target range beyond Rac1.

    Evidence siRNA knockdown in PC12 cells; ELISA-based Cdc42/Rac1 activity assay

    PMID:26911374

    Open questions at the time
    • Single cell line; not confirmed with constitutively active or dominant-negative Cdc42 rescue
    • whether Cdc42 activation is direct or indirect not resolved
  8. 2018 High

    Crystal structure of the FERM domain revealed the lipid-binding surface patch that mediates plasma membrane recruitment, providing the first structural basis for how FARP1 is positioned at membranes to activate downstream GTPases.

    Evidence X-ray crystallography of zebrafish FARP1 FERM domain; in vitro phospholipid binding; charge-patch mutagenesis; cell-based localization and synaptic fractionation

    PMID:29992992

    Open questions at the time
    • No full-length structure; autoinhibitory mechanism between FERM and DH domains remains unknown
    • structure is from zebrafish—human FERM structure not solved
  9. 2021 High

    Demonstrating FARP1 as an essential non-redundant Rac-GEF downstream of EGFR/c-Met/PI3K extended its role from neurons to cancer cell migration, establishing that multiple RTK pathways converge on FARP1 to drive Rac1-dependent membrane ruffling.

    Evidence siRNA/shRNA knockdown in lung adenocarcinoma cells; Rac1 activity assay; live-cell ruffle dynamics; epistasis with EGFR, c-Met, and PI3K inhibitors

    PMID:34731623

    Open questions at the time
    • How PI3K activates FARP1 (direct PH domain engagement vs. intermediate) not resolved
    • in vivo tumor model validation not performed
  10. 2022 High

    Genetic epistasis in Drosophila border cells placed the FARP1 ortholog Cdep downstream of Scribble/Dlg/Lgl polarity proteins and upstream of Rac, establishing a conserved polarity-to-Rac signaling axis for collective cell migration.

    Evidence Scribble/Dlg/Lgl knockdown; Cdep::GFP relocalization rescue; live imaging of border-cell migration in Drosophila

    PMID:36347240

    Open questions at the time
    • Whether Scribble directly binds Cdep/FARP1 or acts indirectly not determined
    • conservation of this polarity pathway in mammalian collective migration not tested
  11. 2023 High

    Identification of a Gβγ/PKCα/FARP1/Cdc42 axis for GPCR-induced tunneling nanotube formation expanded FARP1's functional repertoire to intercellular communication structures and added PKCα as an upstream activator.

    Evidence siRNA knockdown of FARP1; pertussis toxin treatment; PI3K and PKCα inhibitors; Cdc42 activity assay; live imaging of TNTs in adrenocortical cancer cells

    PMID:37390986

    Open questions at the time
    • Whether PKCα directly phosphorylates FARP1 not demonstrated
    • mechanism linking FARP1/Cdc42 to the specific actin architecture of TNTs not resolved
  12. 2026 High

    Demonstrating that GPR81 recruits FARP1 to activate Rac1 for GLUT4 translocation in skeletal muscle revealed a metabolic function for FARP1, connecting lactate sensing to insulin-independent glucose uptake.

    Evidence GPR81 KO mouse; Co-IP of GPR81–FARP1; Rac1 activity assay; GLUT4 translocation assay; LDHA KO for lactate modulation

    PMID:41530347

    Open questions at the time
    • Whether the FERM domain mediates GPR81 binding directly not shown
    • in vivo contribution of FARP1 to whole-body glucose homeostasis not quantified

Open questions

Synthesis pass · forward-looking unresolved questions
  • A full-length structure of FARP1 explaining FERM-mediated autoinhibition and activation mechanisms, along with in vivo genetic models defining its non-redundant roles across tissues, remain central open questions.
  • No full-length FARP1 structure or autoinhibition mechanism defined
  • No FARP1 knockout mouse phenotype reported in the literature
  • Substrate selectivity determinants for Rac1 vs. Cdc42 in different cellular contexts unresolved

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 6 GO:0008092 cytoskeletal protein binding 2 GO:0008289 lipid binding 1
Localization
GO:0005886 plasma membrane 2 GO:0005829 cytosol 1
Pathway
R-HSA-162582 Signal Transduction 6 R-HSA-1266738 Developmental Biology 3 R-HSA-112316 Neuronal System 2
Partners
CDC42GPR81MAP4K4NRP1PLEXINA1PLEXINA4RAC1SYNCAM1

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1997 FARP1 (originally named CDEP) was cloned and characterized as a novel human protein containing an ezrin-like FERM domain (band 4.1 superfamily) and Dbl homology (DH) and pleckstrin homology (PH) domains, establishing its domain architecture as a putative Rho guanine nucleotide exchange factor involved in cytoskeletal organization. cDNA cloning, sequence analysis, Northern blot Biochemical and biophysical research communications Medium 9425278
2001 CDEP/FARP1 DH-PH domain peptide stimulates GDP dissociation from RhoA in vitro, confirming it functions as a Rho guanine nucleotide exchange factor; truncated CDEP induces focus formation in NIH3T3 cells, demonstrating transforming activity. In vitro [3H]GDP dissociation assay using recombinant DH-PH domain peptide; NIH3T3 focus formation assay with truncated CDEP cDNA transfection Osteoarthritis and cartilage High 11680691
2009 FARP1 acts as a specific effector of transmembrane Semaphorin6A/PlexinA4 signaling to promote dendritic growth in lateral motor column (LMC) spinal motor neurons; its Rho-GEF domain is required for this function, and retinoid signaling induces FARP1 expression upstream of this pathway. Loss-of-function and gain-of-function in chick spinal cord; morphological analysis of dendrites; domain deletion (Rho-GEF domain mutant); epistasis with Sema6A/PlexA4 signaling Neuron High 19217374
2012 FARP1 is recruited to the postsynapse where its FERM domain directly binds the synaptic adhesion molecule SynCAM 1, forming a synaptic complex; FARP1 activates Rac1 in spines downstream of SynCAM 1 clustering, promotes F-actin assembly, increases synapse number, modulates spine morphology, and triggers a retrograde signal regulating active zone composition via SynCAM 1. SynCAM 1 requires FARP1 to promote spines, and FARP1 requires SynCAM 1 to elevate spine density (mutual epistasis). Proteomic analysis of SynCAM 1 KO synaptic membranes; co-immunoprecipitation (FERM domain–SynCAM 1); live imaging of dendritic filopodia; overexpression/knockdown with spine/synapse morphology readout; Rac1 activation assay; F-actin staining; genetic epistasis (SynCAM 1 KO × Farp1 manipulation) The Journal of cell biology High 23209303
2014 FARP1 interacts with the Neuropilin-1/PlexinA1 receptor complex and colocalizes with PlexinA1 along dendritic shafts; FARP1 is required for Sema3A-induced dendritic arborization of hippocampal neurons and mediates Sema3A-dependent F-actin redistribution in dendrites. Neuronal activity stabilizes PlexinA1 in dendrites (via proteasome-dependent pathway), gating FARP1-mediated Sema3A responses. Co-immunoprecipitation (FARP1–Neuropilin-1/PlexinA1); immunofluorescence colocalization; FARP1 knockdown with dendritic morphology readout; F-actin distribution assay; neuronal activity manipulation with proteasome inhibition The Journal of neuroscience High 24899721
2015 MAP4K4 directly phosphorylates FARP1 at a pTL motif and co-immunoprecipitates with FARP1; MAP4K4 inhibition increases neurite outgrowth in SH-SY5Y cells, a process known to involve FARP1, suggesting MAP4K4 regulates cytoskeletal dynamics partly via FARP1 phosphorylation. Phosphoproteomic analysis of MAP4K4-inhibited cells; in vitro kinase assay with recombinant proteins; co-immunoprecipitation; neurite outgrowth assay with MAP4K4 inhibitor ACS chemical biology High 26422651
2016 siRNA-mediated knockdown of FARP1 in PC12 cells significantly inhibits Cdc42 activity, establishing FARP1 as a GEF that activates Cdc42 in neuroendocrine cells. siRNA knockdown in PC12 cells; ELISA-based Cdc42/Rac1 activity assay Endocrine-related cancer Medium 26911374
2018 Crystal structures of the FARP1 FERM domain (from zebrafish) revealed a three-lobed clover fold with a conserved positively charged surface patch; in vitro lipid-binding experiments showed the FERM domain binds specific phospholipids via this patch; cell-based analysis demonstrated the positively charged patch mediates plasma membrane localization of FARP1, and FERM domain interactions recruit FARP1 to postsynaptic sites in neurons. X-ray crystallography; in vitro phospholipid-binding assay; mutagenesis of charged surface patch; cell-based localization assay (fluorescence imaging); synaptic fractionation Scientific reports High 29992992
2021 FARP1 acts as an essential Rac-GEF downstream of EGFR and c-Met receptor tyrosine kinases (via the AXL-Gab1-PI3K axis) to drive Rac1-mediated cell migration and ruffle dynamics in human lung adenocarcinoma cells, operating in a non-redundant manner with ARHGEF39 and TIAM2. siRNA/shRNA knockdown; Rac1 activity assay; live-cell imaging of ruffle dynamics; epistasis with RTK inhibitors (EGFR, c-Met) and PI3K inhibitors Cell reports High 34731623
2022 In Drosophila border cells, the FARP1 ortholog Cdep functions downstream of Scribble/Dlg/Lgl basolateral polarity proteins and upstream of Rac to promote follower-cell crawling and cluster cohesion during collective migration; relocalization of Cdep::GFP partially rescues Scribble knockdown, establishing a Scrib/Cdep/Rac epistatic pathway. Genetic epistasis (Scribble, Dlg, Lgl knockdown); live imaging of border-cell migration; Cdep::GFP relocalization rescue experiment; Rac1 activity readout Developmental cell High 36347240
2023 FARP1 mediates Gi/o-coupled GPCR (OXER1, LPA receptor)-induced tunneling nanotube (TNT) formation in adrenocortical cancer cells via a Gβγ/PKCα/FARP1/Cdc42 axis; FARP1 acts downstream of PI3K and PKCα signaling and upstream of Cdc42 to drive actin-rich TNT biogenesis. Pertussis toxin treatment; siRNA knockdown of FARP1; Cdc42 activity assay; pharmacological inhibition (PI3K, PKCα, EGFR transactivation); live imaging of TNT formation The Journal of biological chemistry High 37390986
2026 FARP1 is recruited by the lactate receptor GPR81 to activate RAC1, thereby promoting GLUT4 translocation to the plasma membrane and insulin-independent glucose uptake in skeletal muscle; GPR81 knockout impairs this axis while GPR81 activation enhances it. GPR81 KO mouse model; co-immunoprecipitation (GPR81–FARP1); RAC1 activity assay; GLUT4 translocation assay; genetic upregulation/downregulation of lactate production (LDHA KO) Cell research High 41530347

Source papers

Stage 0 corpus · 21 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2019 LncRNA GLCC1 promotes colorectal carcinogenesis and glucose metabolism by stabilizing c-Myc. Nature communications 283 31375671
2010 Selective isolation of live/dead cells using contactless dielectrophoresis (cDEP). Lab on a chip 178 20126683
2012 The novel synaptogenic protein Farp1 links postsynaptic cytoskeletal dynamics and transsynaptic organization. The Journal of cell biology 90 23209303
2009 FARP1 promotes the dendritic growth of spinal motor neuron subtypes through transmembrane Semaphorin6A and PlexinA4 signaling. Neuron 75 19217374
2014 Activity-dependent regulation of dendritic complexity by semaphorin 3A through Farp1. The Journal of neuroscience : the official journal of the Society for Neuroscience 45 24899721
1997 Molecular cloning and characterization of CDEP, a novel human protein containing the ezrin-like domain of the band 4.1 superfamily and the Dbl homology domain of Rho guanine nucleotide exchange factors. Biochemical and biophysical research communications 31 9425278
2021 FARP1, ARHGEF39, and TIAM2 are essential receptor tyrosine kinase effectors for Rac1-dependent cell motility in human lung adenocarcinoma. Cell reports 29 34731623
2016 Cdc42 and Rac1 activity is reduced in human pheochromocytoma and correlates with FARP1 and ARHGEF1 expression. Endocrine-related cancer 24 26911374
2022 A Scribble/Cdep/Rac pathway controls follower-cell crawling and cluster cohesion during collective border-cell migration. Developmental cell 16 36347240
2018 Structural analyses of FERM domain-mediated membrane localization of FARP1. Scientific reports 15 29992992
2015 MAP4K4 Is a Threonine Kinase That Phosphorylates FARP1. ACS chemical biology 14 26422651
2001 Chondrocyte-derived ezrin-like domain containing protein (CDEP), a rho guanine nucleotide exchange factor, is inducible in chondrocytes by parathyroid hormone and cyclic AMP and has transforming activity in NIH3T3 cells. Osteoarthritis and cartilage 14 11680691
2023 Gi/o GPCRs drive the formation of actin-rich tunneling nanotubes in cancer cells via a Gβγ/PKCα/FARP1/Cdc42 axis. The Journal of biological chemistry 13 37390986
2020 FARP-1 deletion is associated with lack of response to autism treatment by early start denver model in a multiplex family. Molecular genetics & genomic medicine 11 32588496
2017 Alternative cDEP Design to Facilitate Cell Isolation for Identification by Raman Spectroscopy. Sensors (Basel, Switzerland) 7 28208767
2011 Consistent Differential Expression Pattern (CDEP) on microarray to identify genes related to metastatic behavior. BMC bioinformatics 7 22078224
2021 An oncogenic lncRNA, GLCC1, promotes tumorigenesis in gastric carcinoma by enhancing the c-Myc/IGF2BP1 interaction. Neoplasma 6 34196212
2002 [Cloning and characterization of cuticle degrading enzyme CDEP-1 from Beauveria bassiana]. Yi chuan xue bao = Acta genetica Sinica 5 12182086
2019 FARP1 Facilitates Cell Proliferation Through Modulating MAPK Signaling Pathway in Cutaneous Melanoma. The American Journal of dermatopathology 4 31021836
2024 Conserved region of human TDP-43 is structurally similar to membrane binding protein FARP1 and protein chaperons BAG6 and CYP33. microPublication biology 1 39583578
2026 Lactate-activated GPR81/FARP1 signaling drives insulin-independent glucose uptake and metabolic control. Cell research 0 41530347