METTL14-dependent N6-methyladenosine modification of FGF16 participates in IGFBP5 deficiency-enhanced angiogenesis

Abstract N 6 -methyladenosine (m 6 A) RNA modification plays critical roles in physiological and pathological processes. Our prior study demonstrated that IGFBP5 expression is upregulated in the ischemic limb, whereas endothelial-specific IGFBP5 knockout (Igfbp5 EKO ) protects against hind limb ischemia by enhancing angiogenesis. Here, we show that IGFBP5 deficiency elevates global m 6 A levels and upregulates the expression of m 6 A methyltransferase complex components METTL3, METTL14 and WTAP in endothelial cells. We further identified a direct interaction between IGFBP5 and the MT-A70 domain of METTL14. Knockdown of METTL14, METTL3 or WTAP attenuated the pro-angiogenic effects of IGFBP5 deficiency in vitro. In vivo, endothelial knockdown of METTL14 abolished the improved hind-limb ischemia recovery in Igfbp5 EKO mice. Methylated RNA immunoprecipitation sequencing revealed that IGFBP5 depletion in endothelial cells increases both m 6 A modification and mRNA abundance of FGF16. Notably, METTL14 or METTL3 silencing suppressed IGFBP5-dependent FGF16 upregulation. Enhanced translational efficiency of FGF16 in IGFBP5-deficient cells was reversed by METTL14 knockdown, indicating that IGFBP5 regulates FGF16 translation via m 6 A modification. Mechanistically, IGFBP5 modulates FGF16 m 6 A modification via interaction with the m 6 A reader protein IGF2BP2, targeting the m 6 A site at position 255 of FGF16 mRNA. In summary, our study establishes METTL14-mediated m 6 A modification of FGF16 as a key mechanism underlying IGFBP5-driven angiogenesis. Targeting the IGFBP5–METTL14–m 6 A–FGF16 axis may offer novel therapeutic strategies for ischemic disease.