PRSS35

PRSS35 is a secreted serine-protease-family enzyme that remodels the extracellular matrix and processes secreted protein substrates to constrain tissue inflammation and tumor initiation (PMID:36934105, PMID:33780134). It is atypical for its family, carrying a threonine in place of the canonical catalytic serine, and was first identified as a hormonally regulated gene in ovarian theca and granulosa cells (PMID:16870946). The enzyme is matured from a precursor by proprotein-convertase cleavage; in its active form it cleaves CXCL2 at a tandem lysine (KK) motif, lowering CXCL2 levels to limit neutrophil recruitment and neutrophil extracellular trap formation and thereby suppressing hepatocellular carcinoma progression (PMID:36934105). In fibroblasts, PRSS35 binds collagens and collagen-associated proteins and reshapes the matrisome: its ablation in skin produces aberrant ECM collagen composition and increased squamous tumor incidence, identifying an ECM-remodeling, tumor-suppressive role in cancer-associated fibroblasts (PMID:33780134, PMID:37647410). PRSS35 is induced by hyperosmotic stress through p38/JNK signaling and the transcription factors NFAT5 and ATF2, and it limits fibroblast proliferation under these conditions (PMID:37647410). Its collagen-degrading activity is suppressed by HE4/WFDC2, an interaction with functional relevance in kidney fibrosis (PMID:23353556). Despite its hormonal regulation in the reproductive tract, Prss35-knockout mice are fertile with normal ovulation, implantation, and decidualization, indicating PRSS35 is dispensable for female reproduction (PMID:23451081).

1. 2006 Medium

   Established PRSS35 as a serine-protease-family member with an atypical catalytic residue (threonine for serine) and placed its expression in hormonally regulated ovarian cells, framing it as a candidate ovulation-associated enzyme.

   Evidence Subtractive hybridization, bioinformatic/domain analysis, real-time PCR and steroid ablation/replacement with in situ localization in ovary

   PMID:16870946

   Open questions at the time

   • No direct demonstration of catalytic activity or substrate
   • Atypical Thr residue's effect on proteolytic competence not tested
   • Function inferred from expression pattern only
2. 2008 Low

   Extended the hormonal-regulation picture by showing gonadotropin induction across preovulatory follicles and corpus luteum, reinforcing a candidate reproductive role.

   Evidence Microarray and immunolocalization in gonadotropin-induced ovulation in immature mice

   PMID:18566130

   Open questions at the time

   • Expression correlation only, no functional assay
   • No substrate or mechanism
   • Causal role in ovulation untested
3. 2013 Medium

   Tested whether PRSS35 is required for reproduction and found it dispensable, redirecting attention away from an essential reproductive role.

   Evidence Prss35 knockout mice with superovulation, implantation, decidualization and litter-size readouts plus ovariectomy/hormone replacement

   PMID:23451081

   Open questions at the time

   • Clean negative result leaves primary physiological function unidentified
   • Possible redundancy with other proteases not addressed
   • No challenge or stress phenotype examined
4. 2013 Medium

   Connected PRSS35 to ECM proteolysis and disease by identifying it as an HE4/WFDC2 target whose collagen-degrading activity is suppressed, implicating it in renal fibrosis.

   Evidence Myofibroblast expression profiling, protease activity assays with HE4 inhibition, and HE4-neutralizing antibody in three mouse renal disease models

   PMID:23353556

   Open questions at the time

   • Mechanism of HE4 inhibition (direct binding vs. indirect) not resolved
   • Cleavage site on collagen not mapped
   • Single lab
5. 2017 Low

   Placed PRSS35 downstream of inflammatory IL-36α signaling in fibroblasts, linking its expression to tubulointerstitial inflammation.

   Evidence IL-36α stimulation of NIH3T3 fibroblasts with gene expression readout and UUO mouse model

   PMID:29109726

   Open questions at the time

   • Single expression assay without mechanistic follow-up
   • No demonstration of PRSS35 protease activity in this context
   • Causal contribution to inflammation untested
6. 2021 Medium

   Demonstrated a tumor-suppressive function via ECM remodeling, showing CAF-derived PRSS35 controls collagen composition and restrains squamous tumor initiation.

   Evidence Fibroblast expression profiling and PRSS35 ablation in wound-induced and chemically-induced mouse tumor models with collagen composition and tumor incidence readouts

   PMID:33780134

   Open questions at the time

   • Direct collagen substrate and cleavage products not defined
   • Whether tumor suppression requires catalytic activity untested
   • Mechanism linking ECM composition to tumor initiation unclear
7. 2023 High

   Defined PRSS35 maturation and a specific protein substrate, showing proprotein-convertase activation enables KK-motif cleavage of CXCL2 to dampen neutrophil/NET responses and suppress HCC.

   Evidence Biochemical cleavage assays, KK-motif mutagenesis, CXCL2 quantification, neutrophil and NET assays, and in vivo HCC models

   PMID:36934105

   Open questions at the time

   • Full substrate repertoire beyond CXCL2 unknown
   • Structural basis for KK recognition by the atypical active site not solved
   • Identity of the relevant proprotein convertase(s) not specified
8. 2023 Medium

   Established the upstream osmotic-stress signaling that induces PRSS35 and its collagen-binding, matrisome-shaping, anti-proliferative role in fibroblasts.

   Evidence Sorbitol-treated 3D fibroblast cultures with p38/JNK and NFAT5/ATF2 inhibition, proteomic binding-partner and matrisome analysis, and proliferation assays

   PMID:37647410

   Open questions at the time

   • Binding to collagens shown but cleavage of specific collagens not mapped
   • Mechanism linking ECM remodeling to proliferation control unresolved
   • In vivo relevance of osmotic induction not established
9. 2023 Low

   Reinforced the HE4–PRSS35 inhibitory axis in vivo by showing HE4 silencing raises PRSS35 expression and reduces fibrosis in lupus nephritis.

   Evidence HE4 shRNA adenovirus in MRL/LPR mice with Western blotting and histological fibrosis scoring

   PMID:38157023

   Open questions at the time

   • Correlative expression change without direct PRSS35 mechanistic assay
   • Cannot distinguish direct vs. indirect HE4 effect
   • Single method readout
10. 2024 Low

    Refined the osmotic-induction model by showing PRSS35 upregulation via p38 MAPK is dependent on 3D culture dimensionality, indicating mechanical/dimensional context gates its induction.

    Evidence Cyclic hydrostatic pressure and hyperosmotic stress in 3D hydrogels vs. 2D culture with gene expression and pathway analysis

    PMID:38972277

    Open questions at the time

    • Single gene-expression readout, no functional PRSS35 assay
    • Correlative pathway assignment
    • Physiological significance of dimensionality effect unknown

• The full substrate repertoire of PRSS35, the structural basis by which its atypical threonine active site achieves proteolysis, and the unifying physiological function reconciling its reproductive, fibrotic, and anti-tumor roles remain unresolved.
• No structure or catalytic-mechanism model for the Thr-substituted active site
• Substrates beyond CXCL2 and collagens not comprehensively mapped
• No single integrative physiological model across tissues