CLIC3

CLIC3 is a multifunctional protein that drives cancer cell invasion and metastasis by controlling the recycling of pro-invasive cargo from late endosomes/lysosomes to the plasma membrane (PMID:22197222, PMID:25015290, PMID:41933388). Acting together with Rab25, CLIC3 mediates retrograde recycling of ligand-occupied, active-conformation α5β1 integrin to the rear of invading cells, enabling rear-end release during migration on 3D matrices and maintaining active Src signaling (PMID:22197222). Independently of its integrin role, CLIC3 also directs trafficking of the matrix metalloproteinase MT1-MMP (MMP14) from endolysosomal compartments to sites of cell-matrix adhesion, promoting basement membrane disruption and invasion (PMID:25015290). Beyond its intracellular trafficking functions, CLIC3 is secreted by cancer-associated fibroblasts and cancer cells, where it acts as a glutathione-dependent oxidoreductase that reduces transglutaminase-2 (TGM2) and regulates its cofactor binding to drive TGM2-dependent invasion and angiogenesis (PMID:28198360). Genetic knockdown with rescue establishes that CLIC3 supports migration, invasion, anchorage-independent growth, primary tumor growth, and lung metastasis in breast cancer models (PMID:41933388). CLIC3 additionally functions as an NPPB-sensitive outwardly rectifying chloride channel at the plasma membrane (PMID:32066374), interacts with NAT10 to suppress ac4C modification and destabilize p21 mRNA (PMID:38182571), and translocates to the plasma membrane to repress ERK7 and influence cellular senescence (PMID:39809890).

1. 2011 High

   Established CLIC3's first defined function: how active integrin is returned to the cell surface during invasion, identifying CLIC3 as a Rab25-cooperating mediator of retrograde integrin recycling.

   Evidence Photoactivation microscopy, biochemical fractionation, siRNA knockdown with 3D invasion/migration and organotypic Src signaling assays

   PMID:22197222

   Open questions at the time

   • Molecular mechanism by which CLIC3 directs vesicle routing not resolved
   • Direct physical interaction between CLIC3 and Rab25 not biochemically mapped
2. 2012 Medium

   Linked CLIC3 to integrin-mediated endocytic uptake by showing CLT1-induced autophagic tumor cell death requires both α5β1 integrin and CLIC3.

   Evidence Cytotoxicity assays with siRNA knockdown of CLIC3 and α5β1, colocalization of CLT1 with CLIC3 in tumor tissue

   PMID:23204394

   Open questions at the time

   • Mechanistic detail of CLIC3 role in internalization is partial
   • Single lab
3. 2014 High

   Demonstrated a second, integrin-independent trafficking role: CLIC3 routes the metalloproteinase MT1-MMP to adhesion sites, broadening its function in matrix remodeling.

   Evidence siRNA knockdown, immunofluorescence colocalization, 3D Matrigel/collagen invasion and basement membrane disruption assays

   PMID:25015290

   Open questions at the time

   • How CLIC3 distinguishes integrin versus MT1-MMP cargo not defined
   • No structural basis for cargo selection
4. 2017 High

   Revealed an extracellular enzymatic function: secreted CLIC3 acts as a glutathione-dependent oxidoreductase that reduces TGM2, establishing a non-trafficking mechanism for promoting invasion and angiogenesis.

   Evidence Secretome proteomics, in vitro oxidoreductase and TGM2 activity assays, 3D invasion assays, in vivo models, pharmacological TGM2 inhibition

   PMID:28198360

   Open questions at the time

   • Mechanism of CLIC3 secretion not defined
   • Relationship between intracellular trafficking and extracellular oxidoreductase roles unresolved
5. 2020 Medium

   Provided direct electrophysiological evidence that CLIC3 forms a plasma membrane chloride channel, addressing whether CLIC3 retains ion-channel activity in addition to its trafficking and enzymatic roles.

   Evidence Whole-cell patch-clamp electrophysiology, siRNA and overexpression proliferation assays, tissue microarray in gastric cancer cells

   PMID:32066374

   Open questions at the time

   • Channel stoichiometry and gating not characterized
   • Anti-proliferative effect contrasts with pro-invasive roles, context-dependence unexplained
   • Single lab
6. 2024 Medium

   Identified a nuclear/RNA-modification axis: CLIC3 binds NAT10 and inhibits ac4C modification of p21 mRNA, destabilizing p21 to promote proliferation.

   Evidence Co-immunoprecipitation, ac4C modification and mRNA stability assays, in vitro and in vivo proliferation assays in bladder cancer

   PMID:38182571

   Open questions at the time

   • Single Co-IP without reciprocal validation of NAT10 interaction
   • How a trafficking/channel protein accesses NAT10 not explained
   • Single lab
7. 2025 Medium

   Connected CLIC3 to cellular senescence by showing membrane-translocated CLIC3 represses ERK7 and modulates chloride loss, mitochondrial dysfunction, and SASP.

   Evidence RNA-seq, siRNA knockdown in bleomycin senescence model, membrane fractionation, Co-IP with ERK7, chloride and mitochondrial assays

   PMID:39809890

   Open questions at the time

   • ERK7 interaction from single Co-IP
   • Causal link between chloride flux and senescence phenotype not isolated
   • Single lab
8. 2025 Low

   Placed CLIC3 in chemoresistance, proposing it promotes integrin β1 redistribution and PI3K-AKT activation to confer cisplatin resistance.

   Evidence Single-cell transcriptomics, drug sensitivity assays, integrin β1 redistribution imaging, pathway inhibitor experiments in ovarian cancer

   PMID:40515890

   Open questions at the time

   • PI3K-AKT placement is preliminary with limited orthogonal validation
   • Single lab
   • Direct effect on integrin trafficking versus correlation not established
9. 2026 Medium

   Consolidated CLIC3 as a metastasis driver, showing knockdown reduces migration, invasion, and anchorage-independent growth with genetic rescue, and blocks tumor growth and lung metastasis in vivo.

   Evidence shRNA knockdown with shRNA-insensitive rescue construct, migration/invasion/soft-agar assays, mouse mammary fat pad xenograft and lung metastasis model

   PMID:41933388

   Open questions at the time

   • Which mechanistic activity (trafficking, oxidoreductase, channel) drives the in vivo phenotype not dissected
   • Single lab

• How CLIC3's distinct activities—endolysosomal cargo recycling, extracellular oxidoreductase, chloride channel, NAT10/ERK7 interactions—are coordinated or switched in a given cellular context remains unresolved.
• No unifying structural or regulatory mechanism integrating the multiple roles
• Determinants of intracellular versus secreted versus membrane localization unknown