SVIL

SVIL (supervillin) is a membrane- and F-actin-associated scaffolding protein that physically couples the actin cytoskeleton to the plasma membrane and coordinates actomyosin-dependent processes (PMID:9867483). It has a bipartite architecture: an N-terminus carrying nuclear localization signals and a C-terminus bearing villin-homologous actin-binding sequences plus a headpiece (PMID:9867483). During cytokinesis, PLK1 phosphorylates SVIL at Ser238, driving its localization to the central spindle and association with PRC1; in this position SVIL bridges the central spindle and the contractile ring, and its N-terminal myosin-II-binding region is required to activate myosin II at the equatorial cortex for cleavage furrow ingression (PMID:23750008). Beyond cytokinesis, SVIL influences cellular phenotype and motility through actomyosin-linked signaling: its loss in vascular smooth muscle cells shifts cells toward a synthetic phenotype via KLF4/PDGF signaling and alters migration through the RhoA/ROCK pathway (PMID:36475054), and in ovarian cancer cells SVIL supports TGFβ1/Smad2/3 activation to promote proliferation, EMT, and cisplatin resistance under hypoxia (PMID:39197416).

1. 1998 Medium

   Established that SVIL is a high-affinity bridge between F-actin and the plasma membrane, defining the molecular basis for its cytoskeletal scaffolding role and predicting both nuclear and actin-binding functions from its bipartite domain layout.

   Evidence cDNA cloning, sequence/domain analysis, and subcellular fractionation of human supervillin

   PMID:9867483

   Open questions at the time

   • Functional roles of the N-terminal NLS versus C-terminal villin-like domains not tested
   • No direct binding partners beyond F-actin and membrane identified
   • No cellular phenotype assayed
2. 2013 High

   Resolved how SVIL is regulated and deployed during cell division, showing that PLK1 phosphorylation at Ser238 recruits SVIL to the central spindle/PRC1 and that its myosin-II-binding region drives equatorial myosin II activation for furrowing.

   Evidence In vitro PLK1 kinase assay, S238A and domain-deletion mutants (ΔMyo, ΔAct), live-cell imaging, and Co-IP with PRC1

   PMID:23750008

   Open questions at the time

   • Structural basis of SVIL–PRC1 and SVIL–myosin II interactions not defined
   • How phosphorylation directs spindle targeting mechanistically unresolved
   • Whether actin-binding domain contributes to furrowing not separated from myosin role
3. 2022 Medium

   Extended SVIL function to vascular smooth muscle cell identity and motility, linking SVIL loss to phenotypic switching and migration through defined signaling axes.

   Evidence CRISPR/Cas9 knockdown in vSMCs with RNA-seq and phospho-kinase profiling implicating KLF4/PDGF and RhoA/ROCK

   PMID:36475054

   Open questions at the time

   • Direct molecular link between SVIL and KLF4/PDGF or RhoA/ROCK not established
   • Single lab, single cell system
   • Whether effects depend on SVIL's actomyosin scaffolding function untested
4. 2024 Medium

   Placed SVIL in an oncogenic signaling context, showing it supports TGFβ1/Smad2/3-driven EMT, invasion, and chemoresistance in ovarian cancer.

   Evidence siRNA knockdown with functional assays (proliferation, migration, invasion, apoptosis) under hypoxia and a nude mouse in situ tumor model

   PMID:39197416

   Open questions at the time

   • Mechanism by which SVIL activates TGFβ1/Smad2/3 not defined
   • Whether the cytoskeletal scaffolding function mediates the cancer phenotype unknown
   • Single lab, single tumor type

• How SVIL's actin/membrane scaffolding activity mechanistically connects to the diverse signaling pathways (RhoA/ROCK, KLF4/PDGF, TGFβ1/Smad2/3) it influences remains unresolved.
• No direct biochemical link between SVIL and these signaling nodes
• Role of the NLS-bearing N-terminus outside cytokinesis uncharacterized
• No structural model integrating membrane/actin binding with signaling