VIL1

VIL1 (villin-1) is an actin-regulatory protein of absorptive epithelial brush borders that organizes the apical actin cytoskeleton and maintains epithelial barrier integrity (PMID:29274870, PMID:40835194, PMID:24410933). Its F-actin binding is mediated through Cys624: covalent modification of this residue by an enterotoxin triggers F-actin disassembly and barrier failure, while a protective small molecule that shields Cys624 allosterically enhances F-actin binding affinity and preserves barrier integrity (PMID:40835194). Across absorptive cell types VIL1 (and its fish ortholog VILL) is required for formation of apical microvilli (PMID:24410933). In intestinal epithelial cells, VIL1 together with gelsolin is required for dephosphorylation of EIF2A and recovery from cell stress; their chronic loss produces constitutive EIF2A phosphorylation and integrated stress response activation, IRGM1 overexpression, and RIPK3-mediated necroptotic death, with double-knockout mice developing spontaneous Crohn's-like ileitis that is reversed by ISR or RIPK3 inhibition (PMID:29274870, PMID:42254860). In colorectal cancer cells VIL1 suppresses ferroptosis and promotes tumor growth by binding NF-κB p105 and driving NF-κB and lipocalin-2 (LCN2) expression (PMID:39658274). Release of VIL1 from injured brush-border cells into plasma tracks the severity of necroptotic proximal tubular injury (PMID:28704336).

1. 2014 Medium

   Establishing whether villin-1 actively builds apical microvilli rather than merely decorating them, loss-of-function in a fish ortholog tied VILL directly to actin-based microvillus formation in absorptive cells.

   Evidence Morpholino knockdown of VILL in medaka gill ionocytes with immunofluorescence and scanning electron microscopy across salinity conditions

   PMID:24410933

   Open questions at the time

   • Ortholog in a fish model, not direct human VIL1
   • Does not define the molecular mechanism by which VILL nucleates or bundles apical actin
2. 2017 High

   Connecting brush-border actin regulators to epithelial stress recovery, VIL1 and gelsolin were shown to be required for EIF2A dephosphorylation, linking their loss to constitutive stress signaling, necroptosis, and Crohn's-like inflammation.

   Evidence Villin-1/gelsolin double-knockout mice with histology, immunoblots, flow cytometry, electron microscopy, and corroboration in human CD tissue

   PMID:29274870

   Open questions at the time

   • Molecular link between VIL1 and the EIF2A phosphatase machinery not resolved
   • Whether the effect requires VIL1's actin-binding activity is untested
3. 2017 Medium

   Testing whether VIL1 release reports epithelial death, plasmatic villin-1 was shown to rise with proximal tubular injury and to depend on necroptosis, validating it as a necroptosis-linked injury marker.

   Evidence Immunohistochemistry and Western blotting across rat, pig, and human renal/liver injury models with necrostatin-1 intervention

   PMID:28704336

   Open questions at the time

   • Mechanism of VIL1 redistribution and release not defined
   • Single lab; biomarker specificity versus other brush-border proteins unclear
4. 2024 Medium

   Asking how VIL1 influences tumor cell fate, knockout/overexpression in colorectal cancer cells placed VIL1 upstream of ferroptosis suppression via direct NF-κB p105 binding and LCN2 induction.

   Evidence VIL1 knockout/overexpression in CRC lines with xenografts, transcriptomics, immunoblotting, and ferroptosis assays

   PMID:39658274

   Open questions at the time

   • Direct VIL1–NF-κB binding interface not mapped
   • Relationship between VIL1's actin role and NF-κB regulation unknown
   • Single lab
5. 2025 High

   Identifying the molecular site of VIL1's actin control, Cys624 was shown to be the covalently targetable residue governing F-actin binding and barrier integrity.

   Evidence Intestinal organoids, chemical proteomics, Cys624 mutagenesis, in vitro F-actin binding assays, and in vivo barrier validation

   PMID:40835194

   Open questions at the time

   • Structural basis of Cys624-dependent actin binding not resolved
   • Whether physiological modification of Cys624 occurs endogenously is unknown
6. 2026 Medium

   Resolving the causal hierarchy of VIL1-loss pathology, ISR and RIPK3 were placed downstream of VIL1 loss, with pharmacologic inhibition rescuing epithelial architecture and barrier function.

   Evidence Villin-1/gelsolin double-knockout mice and CD patient-derived enteroids with ISR/RIPK3 inhibitor rescue and transepithelial resistance readouts

   PMID:42254860

   Open questions at the time

   • Direct biochemical step connecting VIL1 loss to ISR activation still undefined
   • Single lab extending prior findings

• How VIL1's actin-bundling activity at the brush border mechanistically couples to its roles in EIF2A dephosphorylation and NF-κB binding remains unresolved.
• No structural model linking actin binding to stress-signaling functions
• Whether actin-independent scaffolding underlies the NF-κB and ISR roles is untested