PCSK5 Promotes Angiogenesis and Cardiac Repair After Myocardial Infarction

Background

Key Findings

1. PCSK5 is Upregulated After MI - In Patients and Mice

• Plasma PCSK5 levels were elevated in MI patients compared to controls.
• Plasma PCSK5 positively correlated with VEGFA and GLP-1 levels in acute MI patients.
• PCSK5 expression was specifically upregulated in cardiac endothelial cells (ECs) of MI patients - pointing to an endothelium-specific response to ischemic injury.
• Post-MI plasma PCSK5 levels could predict cardiac function improvement at 6-month follow-up, suggesting biomarker utility.

2. Loss-of-Function: EC-Specific Pcsk5 Deficiency is Damaging

• Endothelial-specific Pcsk5 knockout in male mice impaired angiogenesis and cardiac recovery post-MI.
• The same deficiency delayed tissue repair in a hindlimb ischemia (HLI) model.
• This confirms PCSK5 is non-redundant in ischemia-driven neovascularization.

3. Gain-of-Function: Endothelial Pcsk5 Delivery Improves Outcomes

• Endothelial-specific AAV-mediated Pcsk5 overexpression (AAV-Pcsk5) increased capillary and arteriole densities in infarcted cardiac tissue.
• AAV-Pcsk5 mice showed enhanced VEGF and angiopoietin signaling in cardiac tissue vs. controls by CellChat intercellular communication analysis.
• Fibrosis-related signaling (e.g., periostin/POSTN pathway) was significantly reduced in AAV-Pcsk5 hearts - suggesting PCSK5 promotes repair over scar formation.
• Overexpression improved overall cardiac function post-MI.

4. Mechanism: PCSK5 Directly Cleaves and Activates VEGFA

• PCSK5 acts as a proprotein convertase that directly cleaves VEGFA.
• This cleavage activates VEGFA, which then stimulates VEGFR2 signaling on endothelial cells.
• This drives EC proliferation, migration, and tube formation - the hallmarks of angiogenesis.
• The specific residues Arg158 and Asn164 on PCSK5 are essential for its proteolytic activity and pro-angiogenic function.
• The enhanced VEGFA-VEGFR2 signaling axis was confirmed as the dominant downstream effector.

5. Semaglutide-PCSK5 Axis: A Novel Mechanism for GLP-1RA Cardioprotection

• Semaglutide (a GLP-1 receptor agonist used for T2DM and cardiovascular risk reduction) upregulated PCSK5 expression in ECs via the transcription factor ETS1.
• Semaglutide promoted EC tube formation, migration, and proliferation in vitro - effects that were significantly blunted by PCSK5 knockdown.
• In infarcted mice, semaglutide increased vascular densities and improved cardiac function partially through EC-derived Pcsk5.
• Plasma PCSK5 positively correlated with GLP-1 levels in AMI patients, further supporting this axis in humans.
• This establishes a previously unrecognized mechanism - semaglutide → ETS1 → PCSK5 → VEGFA cleavage → angiogenesis - that may partly explain the cardiovascular benefits of GLP-1 receptor agonists beyond glycemic control and weight loss.

Summary of the Signaling Pathway

Ischemic injury / Semaglutide (via GLP-1R)
            ↓
    ETS1 transcription factor activated in ECs
            ↓
    PCSK5 upregulated & secreted by ECs
            ↓
    PCSK5 cleaves VEGFA (at Arg158/Asn164 active residues)
            ↓
    Mature/active VEGFA → VEGFR2 activation
            ↓
    EC proliferation, migration, tube formation
            ↓
    ↑ Capillary & arteriole density in infarcted tissue
    ↓ Periostin/fibrosis signaling
            ↓
    Improved cardiac function & tissue repair

Clinical Implications

Limitations to Note

• Experiments used male mice only - sex-specific effects are unknown.
• The AAV delivery system is pre-clinical; translation to human gene therapy faces practical hurdles.
• The exact cleavage site on VEGFA and whether other PCSK5 substrates contribute have not been fully mapped.
• The semaglutide-PCSK5 contribution is partial - other mechanisms of semaglutide cardioprotection remain.

What You Need to Understand: PCSK5 in Post-MI Cardiac Repair

1. The Conceptual Novelty - Why This Matters

2. The Biochemical Core: PCSK5 as a VEGFA Sheddase

• Molecular docking showed PCSK5 residues Arg158 and Asn164 interact with VEGFA residues Lys107 and Arg110.
• Cleavage at or near this site generates a more biologically active, soluble VEGFA fragment with greater VEGFR2 binding efficacy.
• Importantly, this is analogous to how PC5 (PCSK5) and furin are already known to process VEGF-C and VEGF-D (the lymphangiogenic VEGFs) - but processing of VEGFA by PCSK5 was previously uncharacterized.
• The Western blot evidence showing cleaved VEGFA in EC supernatant (confirmed in HUVECs transfected with Ad-PCSK5) is the direct biochemical proof.

• Generates a more soluble, receptor-accessible VEGFA isoform.
• Activates downstream VEGFR2 → ERK1/2 phosphorylation (confirmed by pERK Western blots in border zone tissue and in vitro).
• Drives EC proliferation, migration, and tube formation - the three classical angiogenic read-outs.

3. The In Vivo Architecture: What Each Model Proved

4. The Intercellular Communication Layer (CellChat)

• VEGF and angiopoietin signaling flows were enhanced in AAV-Pcsk5 hearts - meaning PCSK5 is shifting the entire intercellular angiogenic network, not just EC-autonomous signaling.
• Periostin (POSTN) signaling - a marker of activated cardiac fibroblasts and adverse remodeling - was reduced. This suggests PCSK5 may indirectly suppress fibroblast activation, possibly by reducing hypoxia or by paracrine signals from healthier endothelium.
• This anti-fibrotic signal is a secondary but clinically important benefit: less scar, more vasculature.

5. The Semaglutide-PCSK5 Axis: Mechanistic and Clinical Depth

• Semaglutide (GLP-1R agonist) activates ETS1, an ETS family transcription factor that binds to promoter elements of the PCSK5 gene in endothelial cells.
• ETS1 is already a known regulator of EC gene expression (VEGFR2, eNOS, VE-cadherin) - finding it upstream of PCSK5 is biologically coherent.
• Semaglutide → GLP-1R → cAMP/PKA → ETS1 activation → PCSK5 transcription is the inferred chain (though not every step was directly shown in the paper).

• Semaglutide's CV benefit (SUSTAIN-6, STEP trials, SELECT trial showing 20% MACE reduction in non-diabetic obese patients) was attributed mainly to anti-atherosclerotic, anti-inflammatory, and weight-loss effects.
• This paper adds a direct vascular repair mechanism - upregulation of an endothelial protease that activates VEGFA and drives neovascularization in infarcted tissue.
• The human correlate (plasma PCSK5 positively correlates with GLP-1 in AMI patients) supports translational relevance.
• Importantly, this effect is partial - ablating EC Pcsk5 blunts but does not eliminate semaglutide's benefit, meaning other pathways (anti-inflammatory, metabolic) still operate.

6. The Biomarker Angle

• Plasma PCSK5 rose after MI and correlated with better cardiac function recovery at 6 months.
• This suggests PCSK5 might stratify patients: those who mount a strong PCSK5 response may have better angiogenic capacity and recover more completely.
• It also correlates with plasma VEGFA - consistent with the mechanism (more PCSK5 → more VEGFA processing → more VEGFA detected or consumed).
• Clinical caveat: this is correlative and needs prospective validation with larger cohorts before it can serve as a clinical biomarker.

7. What the Study Does NOT Show (Critical Gaps)

• Female biology: Only male mice used. Sex differences in angiogenesis and GLP-1R signaling are well-documented; whether PCSK5 behaves identically in females is unknown.
• Precise cleavage site on VEGFA: The Lys107/Arg110 interaction is from molecular docking, not a directly confirmed cleavage site by mass spectrometry. The exact VEGFA fragment generated needs biochemical characterization.
• Other PCSK5 substrates post-MI: PCSK5 has a broad substrate repertoire (BMPs, TGF-β precursors, metalloprotease zymogens, corin). Whether other substrates contribute to the observed phenotype was not fully excluded.
• Long-term safety of PCSK5 upregulation: Sustained VEGFA activation in cardiac tissue raises questions about pathological angiogenesis, vascular permeability, or tumor promotion if applied systemically.
• Human AAV translation: EC-targeted AAV delivery is a major translational hurdle. The specific serotype, promoter (EC-specific like Tie2 or CDH5), and delivery route would need extensive optimization.
• The complete ETS1 pathway: The paper shows semaglutide increases ETS1 and PCSK5 but does not fully map whether this requires direct GLP-1R on ECs or is indirect (e.g., via reduced glucotoxicity, reduced inflammation).

The Single Most Important Insight