Regulation of the proprotein convertases expression and activity during regenerative angiogenesis: Role of hypoxia-inducible factor (HIF)

Proprotein convertases (PCs) are involved in various physiological and pathological processes ranging from embryogenesis to carcinogenesis. Here, using the zebrafish fin regeneration model, we report induced expression of furin and PC5 but not PACE4 and PC7 during fin regeneration that is associated with increased PC activity. Stabilization of HIF by cobalt chloride (CoCl₂₎ further increases these processes. The use of the general PC-inhibitor decanoyl-RVKR-cholromethyl ketone (CMK) inhibited control and CoCl₂-induced PC activity. CoCl₂ inhibits embryonic zebrafish ZF4 cell proliferation and caudal fin regeneration that is associated with the expression of the anti-proliferative genes P21, P16, PC3 and P53 in ZF4 cells and in non-regenerating stump tissues. In contrast, during fin regeneration, HIF stabilization failed to promote the expression of these anti-proliferative genes and maintained high expression of cyclin D. Further analysis revealed that CoCl₂ maintained the formation of immature regenerating vasculature that was associated with amplified expression of OCT4 and various angiogenic factors reported to be PC substrates and/or downstream effectors. These findings revealed that while furin and PC5 expression/activity and their substrates/effectors are regulated during fin regeneration, HIF stabilization by CoCl₂ has the potential to modulate these processes and impact on the regenerative process and vessels organization.