SCIN

SCIN (scinderin) is an actin-cytoskeleton regulatory protein that controls F-actin organization and, through it, cell proliferation, migration, and invasion across multiple cell types (PMID:24212916, PMID:37450577). Its abundance is set post-translationally by the autophagy-lysosome pathway: PIK3C3 (VPS34) kinase activity drives SCIN turnover, and loss of PIK3C3 causes SCIN accumulation; the kinase also phosphorylates HDAC6 at S59, which then deacetylates accumulated SCIN at K189, leading to F-actin disassembly and disruption of Sertoli cell polarity (PMID:37450577). SCIN is further constrained at the transcriptional level by RSRC2, which directly suppresses its expression in triple-negative breast cancer, and post-transcriptionally by miR-301a-5p and by the MEX3A/miR-3163 axis (PMID:34405002, PMID:35490173, PMID:38201443). When SCIN is elevated it promotes proliferation, motility, and epithelial-mesenchymal transition through STAT3 and NF-κB signaling, whereas SCIN loss arrests cells in G0/G1 with upregulation of p21 and CDKN2A, linking its actin function to cell cycle control (PMID:24212916, PMID:25303873, PMID:34405002, PMID:35490173).

1. 2013 Medium

   Established that SCIN is required for cancer cell cycle progression, moving it from an actin-regulatory protein to a driver of proliferation.

   Evidence Lentiviral RNAi knockdown in PC3 prostate cancer cells with flow-cytometry cell cycle analysis and colony formation

   PMID:24212916

   Open questions at the time

   • No rescue experiment to confirm specificity
   • Mechanism linking SCIN actin activity to p21/CDKN2A induction not defined
   • Single cell line
2. 2014 Medium

   Generalized SCIN's proliferative role beyond prostate cancer by showing it controls G0/G1 transition and cyclin expression in lung carcinoma.

   Evidence Lentiviral RNAi knockdown in A549 and H1299 lung carcinoma cells with cell cycle analysis and western blot

   PMID:25303873

   Open questions at the time

   • No rescue
   • Causal link between SCIN and cyclin/PARP changes not mechanistically resolved
   • Single lab
3. 2016 Low

   Provided genetic evidence that SCIN functions in opposition to CDC42 in actin organization, contextualizing its severing/capping role in tumor phenotype.

   Evidence Genome-wide epistasis analysis of CDC42 and SCIN SNPs with melanoma Breslow thickness, replicated in an independent cohort

   PMID:27347659

   Open questions at the time

   • Genetic association only, no direct protein-level experiment
   • Opposing actin roles inferred, not tested here
4. 2021 Medium

   Identified SCIN as a direct target of miR-301a-5p and connected its activity to STAT3/NF-κB-driven proliferation, motility, and EMT in gastric cancer.

   Evidence Dual-luciferase reporter assay, qRT-PCR, functional assays, and pathway inhibition in gastric cancer cells

   PMID:34405002

   Open questions at the time

   • Whether SCIN acts directly on STAT3/NF-κB or indirectly via actin remodeling unresolved
   • Single lab
5. 2022 Medium

   Placed SCIN within an oncogenic regulatory hierarchy downstream of MEX3A/miR-3163 and upstream of NF-κB in nasopharyngeal carcinoma.

   Evidence Expression arrays, rescue experiments, NF-κB inhibition, and in vivo tumor growth in NPC models

   PMID:35490173

   Open questions at the time

   • No direct MEX3A-SCIN binding shown
   • Mechanism by which SCIN activates NF-κB not defined
6. 2023 High

   Defined the post-translational control of SCIN abundance, showing PIK3C3-dependent autophagy degrades SCIN and an HDAC6-mediated K189 deacetylation event governs its effect on F-actin and cell polarity.

   Evidence Sertoli-cell-specific Pik3c3 conditional knockout mouse with proteomics, phosphoproteomics, autophagy/proteasome pathway analysis, and site-specific mutagenesis of HDAC6 S59 and SCIN K189

   PMID:37450577

   Open questions at the time

   • Direct demonstration of K189 acetylation altering SCIN severing/capping activity in vitro not shown
   • How deacetylated SCIN drives F-actin disassembly mechanistically incomplete
7. 2023 Medium

   Established RSRC2 as a direct transcriptional repressor of SCIN whose tumor-suppressive effects in TNBC are mediated by keeping SCIN low.

   Evidence ChIP-seq, ChIP-qPCR, transcriptome arrays, rescue experiments, and a metastatic mouse model in triple-negative breast cancer cells

   PMID:38201443

   Open questions at the time

   • Downstream effectors of SCIN in TNBC adhesion/invasion not fully resolved
   • Single lab
8. 2025 Low

   Connected SCIN to oxygen-sensitive signaling by placing it downstream of HIF-1α in controlling chondrocyte F-actin dynamics and dedifferentiation.

   Evidence 3D chondrogenic organoid and in vivo osteoarthritis models with pharmacological RhoA/ROCK and HIF-1α/SCIN pathway manipulation

   PMID:41135736

   Open questions at the time

   • HIF-1α→SCIN axis inferred pharmacologically, not directly validated
   • Abstract-level mechanistic detail only

• How SCIN's calcium-regulated actin severing/capping activity is biochemically coupled to its downstream effects on STAT3/NF-κB signaling and cell cycle arrest remains unresolved.
• No in vitro reconstitution linking acetylation state to actin-severing activity
• Direct molecular bridge between SCIN actin remodeling and transcriptional/cell cycle outputs not established