VASN

VASN is a TGF-β-inducible transmembrane glycoprotein that acts as a multifunctional signaling hub coordinating receptor pathway activation, lysosomal quality control, and tumor progression (PMID:40297901, PMID:41630427). At the lysosome, VASN interacts with mTOR and STK11IP and disrupts the STK11IP-mTOR-V-ATPase complex to promote lysosomal acidification, a function required for TGF-β-induced mitophagy, terminal erythroid differentiation, and progression of mutant KRAS-driven lung cancer (PMID:41630427). In endothelial cells, VASN operates downstream of the transcription factor KLF15, which binds GC-rich elements in the VASN promoter to activate its expression; VASN then suppresses angiogenic function by engaging Dll4-induced Notch1 signaling through its EGF-like domain, which is essential for the VASN-Notch1 interaction (PMID:40297901). Across multiple carcinomas, VASN promotes proliferation, migration, invasion, and EMT by acting upstream of the YAP/TAZ transcriptional program — it physically binds YAP, inhibits its phosphorylation, and activates YAP/TAZ-TEAD targets together with the PTEN/PI3K/AKT axis (PMID:32633347, PMID:36468780), and in colorectal cancer it additionally interacts with NOTCH1 to co-activate NOTCH and MAPK signaling, driving metastasis and drug resistance (PMID:39107788). VASN expression is induced under hypoxia by HIF-1α, including H. pylori-driven HIF-1α in gastric cancer where VASN activates COL4A1/PI3K/AKT signaling (PMID:40550854). In vivo, VASN knockout produces myocardial fibrosis and pathological cardiac hypertrophy, establishing a role in cardiac tissue homeostasis (PMID:39898320, PMID:41235503).

1. 2012 Medium

   Establishing where VASN is expressed was the first step toward assigning physiological function; mapping its expression domains anchored later mechanistic work in vascular and developmental tissues.

   Evidence Whole-mount in situ hybridization and Vasn-lacZ knock-in β-galactosidase reporter in mice

   PMID:22426063

   Open questions at the time

   • Expression mapping does not establish molecular function
   • No protein-level localization within cells
   • Causal role in any tissue not tested
2. 2019 Low

   The first link of VASN to a defined oncogenic effector came from showing its loss suppresses YAP/TAZ pathway components and EMT markers in cancer cells, placing it within Hippo-pathway-associated tumor biology.

   Evidence siRNA knockdown with migration/invasion/proliferation assays and Western blot in thyroid cancer cells

   PMID:31312369

   Open questions at the time

   • Single knockdown approach without rescue
   • Correlation between VASN and YAP/TAZ not mechanistically dissected
   • No direct interaction shown
3. 2021 Medium

   Whether VASN was upstream or downstream of YAP/TAZ was resolved by epistasis: YAP overexpression rescued the proliferation defects caused by VASN knockdown, positioning VASN upstream of the Hippo effectors.

   Evidence siRNA knockdown plus YAP overexpression rescue in prostate and laryngeal cancer cells with viability/colony assays

   PMID:32633347 PMID:34565020

   Open questions at the time

   • Mechanism by which VASN regulates YAP not defined
   • No physical interaction demonstrated at this stage
   • Single-lab contexts
4. 2023 Medium

   The molecular basis of VASN-YAP regulation was clarified by demonstrating physical interaction and inhibition of YAP phosphorylation, linking VASN to both YAP/TAZ-TEAD targets and the PTEN/PI3K/AKT pathway.

   Evidence Reciprocal co-IP, co-immunofluorescence, Western blot, and YAP knockdown rescue in colorectal cancer cells

   PMID:36468780

   Open questions at the time

   • Direct binding interface not mapped
   • How a transmembrane protein modulates YAP phosphorylation mechanistically unresolved
   • Single lab
5. 2024 Medium

   VASN was shown to engage a second receptor pathway, interacting with NOTCH1 to co-activate NOTCH and MAPK signaling, and its activity as a secreted/inducible factor was tied to chromatin regulator ARID1A.

   Evidence Co-IP, secretome proteomics, ARID1A knockdown/restoration, recombinant VASN treatment and Notch1 knockdown in colorectal and lung adenocarcinoma cells

   PMID:39107788 PMID:39472811

   Open questions at the time

   • VASN-NOTCH1 binding interface not defined
   • Relationship between YAP and NOTCH branches of VASN signaling unclear
   • Secretion mechanism not characterized
6. 2025 High

   A definitive upstream transcriptional regulator and a domain-resolved effector mechanism were established: KLF15 directly activates VASN, which suppresses angiogenesis via Dll4-Notch1 signaling requiring its EGF-like domain.

   Evidence ChIP-seq, ATAC-seq, endothelial-specific KLF15 and VASN conditional KO mice, retinal angiogenesis assays, γ-secretase inhibitor rescue, and EGF-like domain peptide experiments

   PMID:40297901

   Open questions at the time

   • Whether the EGF-domain/Notch1 mechanism operates identically in tumor contexts not tested here
   • Reconciliation of pro-tumor versus anti-angiogenic roles incomplete
7. 2025 Medium

   Hypoxia-driven and infection-driven induction of VASN was placed under HIF-1α control, identifying COL4A1 as a downstream effector feeding PI3K/AKT in gastric cancer and reinforcing YAP/TAZ-PTEN/AKT regulation in bladder cancer.

   Evidence Hypoxia culture, HIF-1α/VASN siRNA, VASN heterozygous KO mice, gastric cell KD/OE, RNA-seq and proteomics

   PMID:40550854 PMID:40594164

   Open questions at the time

   • Direct HIF-1α binding at the VASN promoter not shown in these entries
   • COL4A1 regulation mechanism not fully dissected
   • Bladder cancer findings rely on single siRNA approach
8. 2025 Medium

   Loss-of-function in vivo revealed organ-level roles for VASN in the heart, showing knockout induces myocardial fibrosis and pathological hypertrophy with altered ECM, inflammatory, and contractile-pathway signatures.

   Evidence VASN knockout mice with histology, RNA-seq, exosome sequencing, qPCR and Western blot

   PMID:39898320 PMID:41235503

   Open questions at the time

   • Direct molecular link between VASN and contractile/p-MLC2 pathways is correlative
   • Cardiac cell type responsible not defined
   • Mechanism connecting VASN loss to fibrosis unresolved
9. 2026 High

   The most mechanistically resolved function was defined at the lysosome, where VASN disrupts the STK11IP-mTOR-V-ATPase complex to drive acidification, mitophagy, erythroid differentiation, and KRAS-driven lung cancer, with parallel mitochondrial enrichment seen in HCC.

   Evidence LysoIP, co-IP, CLEM/FIB-SEM, subcellular fractionation, immunoelectron microscopy, and loss-of-function studies across erythroid, lung cancer, and HCC models

   PMID:41630427 PMID:42118142

   Open questions at the time

   • How a transmembrane glycoprotein reaches the lysosomal mTOR complex not detailed
   • Mitochondrial localization functional role remains correlative
   • Relationship between lysosomal and receptor-signaling functions not integrated

• It remains unresolved how VASN's distinct molecular activities — lysosomal complex disruption, EGF-domain-mediated Notch1 engagement, direct YAP binding, and TGF-β trapping — are coordinated within a single protein, and whether they operate in the same or distinct cellular pools.
• No structural model relating VASN domains to its multiple binding partners
• Determinants of subcellular routing (lysosome vs plasma membrane vs secretion) unknown
• Context that selects YAP vs NOTCH vs lysosomal outputs undefined