FERMT3

FERMT3 encodes kindlin-3, a FERM-domain adaptor protein required for integrin function in hematopoietic cells (PMID:19064721, PMID:20216991). Truncating loss-of-function mutations that ablate kindlin-3 protein in leukocytes and platelets cause leukocyte adhesion deficiency type III (LAD-1/variant syndrome), establishing kindlin-3 as essential for inside-out integrin activation (PMID:19064721). In patient cells lacking functional kindlin-3, activation of the platelet integrin αIIbβ3, the α2β1-integrin response, Rap-1 activation, and leukocyte adhesion to VCAM-1 and endothelium are all severely impaired, and these defects are corrected by hematopoietic stem cell transplantation, confirming the causal hematopoietic role (PMID:20216991). Beyond its canonical integrin function, FERMT3 modulates Wnt/β-catenin signaling across non-hematopoietic contexts: it acts through integrin-mediated Wnt/β-catenin signaling to regulate glioma proliferation and temozolomide chemoresistance (PMID:28778805), inhibits Wnt/β-catenin to suppress smoke-induced EMT, migration, and cell-cycle progression in lung epithelial cells (PMID:34742298), and suppresses colorectal cancer invasion and 5-FU resistance while enhancing NK-cell killing by lowering β-catenin-driven PD-L1 expression (PMID:35672907). FERMT3 is also expressed in keloid macrophages and fibroblasts, where its modulation alters cellular metabolism, cytokine output, proliferation, and migration (PMID:40928556).

1. 2003 Low

   Established the domain architecture and likely localization of the FERMT3 product, framing it as a candidate membrane adaptor at integrin adhesion sites before any direct function was known.

   Evidence Proteomic identification from plasma-membrane fractions with bioinformatic domain analysis and reference to C. elegans UNC-112 colocalization with integrin

   PMID:12886250

   Open questions at the time

   • No direct functional assay performed on the FERMT3 protein itself
   • Integrin localization inferred from an ortholog, not demonstrated for human kindlin-3
   • No interactome or activation mechanism defined
2. 2008 High

   Answered whether FERMT3 is genetically required for integrin function in humans by showing truncating mutations ablate kindlin-3 protein and cause LAD-1/variant syndrome.

   Evidence Homozygosity mapping and Sanger sequencing identifying premature stop codons across independent families, with western blot confirming absent protein in patient leukocytes and platelets

   PMID:19064721

   Open questions at the time

   • Molecular mechanism by which kindlin-3 activates integrins not resolved at structural level
   • Did not dissect cell-type-specific contributions
3. 2010 High

   Defined the functional consequences of kindlin-3 loss and proved causality, showing impaired inside-out activation of multiple integrins and Rap-1 signaling that is reversed by transplantation.

   Evidence Flow cytometry, platelet aggregation/secretion, Rap-1 activation, adhesion assays in patient cells with the R573X mutation, plus HSCT rescue

   PMID:20216991

   Open questions at the time

   • Direct biochemical link between kindlin-3 and Rap-1 not established
   • Order of events in the integrin activation cascade not resolved
4. 2017 Medium

   Extended FERMT3 function beyond hematopoietic adhesion by linking it to integrin-mediated Wnt/β-catenin signaling controlling glioma proliferation and chemoresistance.

   Evidence siRNA knockdown with proliferation assays, TOPflash/FOPflash Wnt reporter, and western blot in glioblastoma cells

   PMID:28778805

   Open questions at the time

   • No rescue or mutagenesis to confirm specificity
   • Mechanistic coupling between integrin and Wnt not biochemically defined
   • Single cancer context
5. 2021 Medium

   Showed FERMT3 can act as a suppressor of EMT and migration through Wnt/β-catenin inhibition in non-cancer epithelial cells under environmental stress.

   Evidence FERMT3 overexpression with EMT-marker and Wnt pathway western blots, migration assay, and cell-cycle analysis in A549 cells

   PMID:34742298

   Open questions at the time

   • Single cell line and single lab
   • Direction of effect opposite to glioma context not reconciled mechanistically
   • No loss-of-function confirmation
6. 2022 Medium

   Connected FERMT3-mediated Wnt suppression to tumor immune evasion by demonstrating that lowering β-catenin reduces PD-L1 and enhances NK-cell killing in colorectal cancer.

   Evidence Overexpression/knockdown with invasion, apoptosis, NK co-culture cytotoxicity assays, β-catenin/PD-L1 western blots, and Wnt-agonist rescue

   PMID:35672907

   Open questions at the time

   • Single lab without in vivo validation
   • Mechanism linking FERMT3 to β-catenin level not defined
   • PD-L1 regulation shown correlatively at protein level
7. 2025 Medium

   Identified a stromal/immune expression niche for FERMT3 in keloid tissue and linked it to cellular metabolism and inflammatory output.

   Evidence scRNA-seq localization plus in vitro modulation in macrophages and fibroblasts with metabolic, cytokine, proliferation, and migration assays

   PMID:40928556

   Open questions at the time

   • Molecular pathway linking FERMT3 to metabolic reprogramming not defined
   • Correlative single-lab data without genetic rescue
   • Integrin or Wnt involvement not tested in this context

• How kindlin-3's canonical integrin-activation function mechanistically connects to the context-dependent Wnt/β-catenin modulation reported in non-hematopoietic cells remains unresolved.
• No structural or biochemical mechanism coupling integrin engagement to β-catenin levels
• Opposing effects across tissues not reconciled
• No in vivo demonstration of the Wnt-regulatory role