Heat shock protein 90 stabilizes CD93 glycosylation to influence angiogenesis during diabetic wound healing

BACKGROUND: Angiogenesis, the formation of new blood vessels from preexisting vasculature, is often impaired in pathological conditions, such as a hyperglycemic environment. Angiogenesis is tightly regulated by a balance of proangiogenic and antiangiogenic factors. CD93, a glycoprotein expressed on endothelial cells (ECs), has been identified as a significant proangiogenic factor. However, the specific impact of its glycosylation, particularly O-GlcNAcylation, on endothelial cell function and angiogenesis remains entirely unexplored. Therefore, this study aimed to elucidate the role of CD93 glycosylation in angiogenesis and uncover the underlying molecular mechanism, especially under high glucose conditions. METHODS: siCD93 was used to evaluate the role of CD93 in endothelial cell angiogenesis. Tube formation, spheroid sprouting assays, Transwell assays, and adhesion assays were used to assess the angiogenic capability, migration, and adhesion, respectively. Co-immunoprecipitation coupled with mass spectrometry (Co-IP-MS) was employed to identify CD93-interacting proteins. A murine dorsal skin wound model was used to elucidate its role in angiogenesis during wound healing. RESULTS: siCD93 significantly impaired angiogenesis by inhibiting migration and adhesion without affecting proliferation or cell cycle in ECs. CD93 O-GlcNAcylation modulated its proangiogenic function, whereas high-glucose treatment downregulated both CD93 expression and its O-GlcNAcylation. CD93 overexpression partially rescued the angiogenic impairment induced by high glucose. In vivo studies further indicated that CD93 knockout exacerbated wound healing delay in diabetic wounds. Mechanistically, heat shock protein 90 (HSP90) interacted with the extracellular domain of CD93 to stabilize CD93 O-GlcNAcylation and protect it from ubiquitin-proteasomal degradation. The HSP90-CD93 interaction enabled CD93 to activate the downstream focal adhesion kinase (FAK) signaling pathway, thereby promoting angiogenesis. In vivo experiments further confirmed that HSP90 inhibition impaired the proangiogenic effects of recombinant CD93 protein (rCD93) in skin wound healing. CONCLUSIONS: CD93 promotes angiogenesis dependent on O-GlcNAcylation. Under high glucose, CD93 expression and its O-GlcNAcylation are downregulated, leading to impaired angiogenesis. Mechanistically, HSP90 interacts with CD93 to stabilize it against ubiquitin-proteasomal degradation, thereby maintaining O-GlcNAcylation homeostasis and activating the downstream FAK signaling pathway. Our findings identify the HSP90-CD93 interaction as a potential therapeutic target for angiogenesis-related disorders.