Affinage

FRMD8

FERM domain-containing protein 8 · UniProt Q9BZ67

Length
464 aa
Mass
51.2 kDa
Annotated
2026-06-09
13 papers in source corpus 7 papers cited in narrative 7 extracted findings
Cross-family judge vs UniProt: tie faithfulness: 5/6 claims corpus-supported (83%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

FRMD8 (iTAP) is a FERM domain-containing adaptor protein that functions as a stabilising subunit of the iRhom/ADAM17 sheddase complex, governing regulated ectodomain shedding at the cell surface (PMID:29897336, PMID:29897333). It binds directly to the cytoplasmic N-terminus of iRhom proteins and prevents endolysosomal degradation of iRhom2 and ADAM17 (TACE), thereby maintaining the active sheddase pool; loss of FRMD8 destabilises this complex and impairs ADAM17-mediated shedding of TNFα and EGF receptor ligands (PMID:29897336, PMID:29897333). Through this activity FRMD8 controls inflammatory responses and intestinal epithelial barrier repair in vivo, and influences cancer cell growth both cell-autonomously and via the tumour microenvironment (PMID:36720499); in BRCA1-mutant triple-negative breast cancer, low FRMD8 fails to support iRhom2-dependent cleavage of transmembrane TNFα, retaining it at the surface and promoting metastasis (PMID:40619383). Independently of its sheddase role, FRMD8 acts as a cell-cycle and tumour suppressor: it binds CDK7 and CDK4 to disrupt the CDK7–CDK4 interaction and inhibit CDK4 activation, and competes with MDM2 for RB to attenuate MDM2-mediated RB degradation, with Frmd8 loss accelerating colorectal adenoma formation (PMID:37527040). FRMD8 also protects estrogen receptor α by disrupting the UBE3A–ERα interaction to block its ubiquitin-mediated degradation, while supporting ESR1 transcription through FOXO3A (PMID:40213945). FRMD8 expression is itself repressed by MALAT1-directed recruitment of PRC2 to its locus (PMID:41985336).

Mechanistic history

Synthesis pass · year-by-year structured walk · 7 steps
  1. 2018 High

    Established FRMD8/iTAP as a previously unrecognised stabilising component of the iRhom2/ADAM17 sheddase complex, answering how the active sheddase machinery is maintained at the cell surface.

    Evidence Co-IP/mass-spectrometry interactome, reciprocal Co-IP, knockdown/knockout in iPSC-derived human macrophages and mouse tissues, cell-surface stability and endolysosomal inhibition assays; replicated in two independent eLife papers

    PMID:29897333 PMID:29897336

    Open questions at the time
    • Structural basis of FRMD8 binding to the iRhom N-terminus not resolved
    • Mechanism by which the complex is diverted from endolysosomal degradation not defined at molecular detail
  2. 2018 High

    Demonstrated functional consequence of the interaction: FRMD8 depletion impairs TNF production and depletes active TACE, linking the adaptor to inflammatory cytokine output.

    Evidence IP/MS, siRNA knockdown in primary human macrophages, iTAP KO mouse tissue analysis, lysosomal degradation assays

    PMID:29897333

    Open questions at the time
    • Whether FRMD8 selectively affects subsets of ADAM17 substrates not fully delineated
  3. 2023 Medium

    Extended the sheddase role to physiology and disease, showing iTAP/FRMD8 controls inflammation, intestinal barrier repair, and cancer growth in vivo.

    Evidence Frmd8 KO mouse phenotyping, in vivo tumor growth assays, inflammatory challenge experiments

    PMID:36720499

    Open questions at the time
    • Cell-autonomous versus microenvironmental contributions not fully separated
    • Single lab
  4. 2023 Medium

    Revealed a sheddase-independent tumour-suppressor function, showing FRMD8 restrains the cell cycle by disrupting CDK7–CDK4 and competing with MDM2 to stabilise RB.

    Evidence Reciprocal Co-IP, competitive and peptide competition binding assays, CDK4 activation and RB stability assays, Frmd8 KO AOM/DSS colorectal model

    PMID:37527040

    Open questions at the time
    • Structural detail of the competitive interactions absent
    • Relationship between this nuclear/cell-cycle role and the membrane sheddase role unclear
    • Single lab
  5. 2025 Medium

    Identified a further regulatory role in hormone receptor stability, with FRMD8 protecting ERα from UBE3A-mediated degradation and supporting ESR1 transcription via FOXO3A.

    Evidence Co-IP, competitive binding and ERα stability assays, gene expression analysis, MMTV-Cre;Frmd8;PyMT mouse model, single-cell RNA profiling

    PMID:40213945

    Open questions at the time
    • Subcellular site of the FRMD8–UBE3A–ERα interplay not defined
    • Mechanism linking FRMD8 to FOXO3A regulation unresolved
    • Single lab
  6. 2025 Medium

    Connected FRMD8 loss to metastasis in BRCA1-mutant TNBC through failure to shed transmembrane TNFα, tying the sheddase mechanism to a clinical cancer phenotype.

    Evidence Library screening, cellular functional assays, in vivo metastasis model, iRhom2 degradation assays, pharmacological rescue with paclitaxel and etanercept

    PMID:40619383

    Open questions at the time
    • Generalisability beyond BRCA1-mutant context untested
    • Single lab
  7. 2026 Medium

    Defined upstream transcriptional control of FRMD8, showing MALAT1 recruits PRC2 to repress FRMD8 and thereby tune ADAM17 activity.

    Evidence RNA pull-down, RIP, ChIP-PCR, MALAT1 knockdown, pharmacological ADAM17 and EZH2 inhibition in trophoblast cells

    PMID:41985336

    Open questions at the time
    • Direct PRC2 occupancy dynamics at the FRMD8 locus not time-resolved
    • Relevance of this axis outside trophoblast cells untested
    • Single lab

Open questions

Synthesis pass · forward-looking unresolved questions
  • How FRMD8's membrane sheddase-stabilising activity and its distinct nuclear/cell-cycle and receptor-stabilising functions are coordinated within a single cell remains unresolved.
  • No structural model integrating the multiple binding partners
  • Whether subpopulations or post-translational states partition FRMD8 between these roles is unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 4 GO:0098772 molecular function regulator activity 4
Localization
GO:0005886 plasma membrane 2
Pathway
R-HSA-168256 Immune System 3 R-HSA-1640170 Cell Cycle 1
Complex memberships
iRhom2/ADAM17 sheddase complex

Evidence

Reading pass · 7 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2018 FRMD8 (iTAP) is a component of the iRhom2/ADAM17 sheddase complex, binding directly to the cytoplasmic N-terminus of iRhom proteins; it is necessary to stabilise iRhom2 and ADAM17 at the cell surface, and in its absence iRhom2 and ADAM17 are degraded via the endolysosomal pathway, resulting in reduced ADAM17-mediated shedding of TNFα and EGF receptor ligands. Co-immunoprecipitation/mass spectrometry screen, reciprocal Co-IP, genetic knockdown/knockout in iPSC-derived human macrophages and mouse tissues, cell-surface stability assays, endolysosomal pathway inhibition experiments eLife High 29897333 29897336
2018 FRMD8/iTAP binds to iRhom proteins and enhances their cell-surface stability, preventing degradation of iRhom and TACE (ADAM17) in lysosomes; depletion of iTAP in primary human macrophages profoundly impaired TNF production, and tissues from iTAP KO mice show pronounced depletion of active TACE levels. Immunoprecipitation/mass spectrometry, siRNA knockdown in primary human macrophages, iTAP KO mouse tissue analysis, lysosomal degradation assays eLife High 29897333
2023 iTAP/FRMD8 KO mice exhibit defects in inflammatory responses and intestinal epithelial barrier repair; iTAP/FRMD8 also regulates cancer cell growth in a cell-autonomous manner and by modulating the tumor microenvironment, consistent with its role in controlling ADAM17 sheddase complex stability. iTAP/Frmd8 KO mouse phenotyping, in vivo tumor growth assays, inflammatory challenge experiments Life science alliance Medium 36720499
2023 FRMD8 interacts separately with CDK7 and CDK4, disrupts the CDK7–CDK4 interaction to inhibit CDK4 activation, and competes with MDM2 to bind RB, thereby attenuating MDM2-mediated RB degradation and causing cell-cycle arrest. Frmd8 deficiency in mice accelerates colorectal adenoma formation. Co-immunoprecipitation, competitive binding assays, CDK4 activation assays, RB stability assays with MDM2, Frmd8 KO mouse AOM/DSS colorectal cancer model, peptide competition experiments Cell reports Medium 37527040
2025 FRMD8 interacts with both ERα and UBE3A (an E3 ubiquitin ligase), and disrupts the UBE3A–ERα interaction, thereby blocking UBE3A-mediated ERα degradation; FRMD8 deficiency also suppresses ESR1 transcription via downregulation of FOXO3A, a transcription factor for ESR1. Co-immunoprecipitation, competitive binding assays, ERα protein stability assays, gene expression analysis, MMTV-Cre; Frmd8; PyMT mouse model, single-cell RNA profiling eLife Medium 40213945
2025 In BRCA1-mutant TNBC cells, low FRMD8 expression inhibits cleavage of transmembrane TNF-α (tmTNF-α) and promotes surface tmTNF-α expression by failing to prevent iRhom2 degradation through the endocytic pathway, thereby promoting metastasis. Library screening, cellular functional assays, in vivo metastasis animal experiments, iRhom2 degradation assays, pharmacological rescue with paclitaxel and etanercept Cellular & molecular biology letters Medium 40619383
2026 MALAT1 recruits PRC2 (Polycomb Repressive Complex 2) to transcriptionally repress FRMD8; MALAT1 knockdown upregulates FRMD8, which stabilises ADAM17 and enhances its proteolytic activity. RNA pull-down, RIP, and ChIP-PCR assays established the MALAT1–PRC2–FRMD8–ADAM17 regulatory axis in trophoblast cells. RNA pull-down, RNA immunoprecipitation (RIP), ChIP-PCR, MALAT1 knockdown, pharmacological ADAM17 inhibition, EZH2 inhibition European journal of cell biology Medium 41985336

Source papers

Stage 0 corpus · 13 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1997 A critical role for tapasin in the assembly and function of multimeric MHC class I-TAP complexes. Science (New York, N.Y.) 411 9271576
1996 Deglucosylation of N-linked glycans is an important step in the dissociation of calreticulin-class I-TAP complexes. Proceedings of the National Academy of Sciences of the United States of America 75 8943049
2018 FRMD8 promotes inflammatory and growth factor signalling by stabilising the iRhom/ADAM17 sheddase complex. eLife 64 29897336
2018 iTAP, a novel iRhom interactor, controls TNF secretion by policing the stability of iRhom/TACE. eLife 56 29897333
2023 FRMD8 targets both CDK4 activation and RB degradation to suppress colon cancer growth. Cell reports 11 37527040
2023 The ADAM17 sheddase complex regulator iTAP/Frmd8 modulates inflammation and tumor growth. Life science alliance 10 36720499
2024 LINC01002 functions as a ceRNA to regulate FRMD8 by sponging miR-4324 for the development of COVID-19. Virology journal 5 38734674
2015 iTAP: integrated transcriptomics and phenotype database for stress response of Escherichia coli and Saccharomyces cerevisiae. BMC research notes 2 26653323
2010 Induced adult stem (iAS) cells and induced transit amplifying progenitor (iTAP) cells-a possible alternative to induced pluripotent stem (iPS) cells? Journal of tissue engineering and regenerative medicine 2 19967742
2025 Loss function of tumor suppressor FRMD8 confers resistance to tamoxifen therapy via a dual mechanism. eLife 1 40213945
2025 FRMD8 inhibits tumor metastasis in BRCA1-associated TNBC by negatively regulating tmTNF-α. Cellular & molecular biology letters 1 40619383
2024 Mechanical load applied by Intraosseous Transcutaneous Amputation Prosthesis (ITAP) during walking on level and sloped treadmill: A case study. Medical engineering & physics 1 38418026
2026 Connecting chromatin to cell invasion: MALAT1-PRC2 complex epigenetically controls trophoblast activity via FRMD8-ADAM17-protease inhibitor circuit. European journal of cell biology 0 41985336

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