Fig. 5. SRF mediates the positive regulation of MAMs on VEGFR2 expression.

a HUVECs were pre-transfected with or without FUNDC1 siRNA for 24 h, then treated with actinomycin D for different periods of time. RT-qPCR assay analysis of vascular endothelial growth factor receptor 2 (VEGFR2) mRNA levels (n = 5 independent experiments). b HUVECs were pre-transfected with or without FUNDC1 siRNA for 24 h, then transfected with various VEGFR2 promoter truncation constructs or a mutant (serum response factor [SRF] binding site) construct for 24 h. After this, luciferase activity was measured (n = 5 independent experiments). c Chromatin immunoprecipitation assays using an anti-SRF antibody to amplify VEGFR2 promoter in HUVECs transfected with or without FUNDC1 siRNA (n = 5 independent experiments). d HUVECs were pre-transfected with or without FUNDC1 siRNA for 24 h and then treated with VEGF for 30 min. Expression of SRF and phosphorylated SRF at Ser103 (pSRF) was determined by western blot assay (n = 5 independent experiments). e Cytosolic Ca²⁺ levels, as indicated by the fluorescent probe Fluo-4, AM (n = 5 independent experiments). HUVECs were transfected with Scr siRNA or FUNDC1 siRNA for 24 h and then exposed to VEGF (20 ng/mL) for the indicated times. f HUVECs were infected with adenovirus encoding control (Ad-Cont) or mitochondrial–endoplasmic reticulum (ER) linker (Ad-Linker) for 24 h and then treated with BAPTA-AM (10 µM) or control dimethylsulfoxide (vehicle) for 30 min. Levels of SRF and pSRF (Ser103) were detected by western blot assay (n = 5 independent experiments). g HUVECs were pre-transfected with or without SRF siRNA for 24 h, then infected with adenovirus encoding control or mitochondria–ER linker for 24 h. VEGFR2 protein expression was detected by western blot assay (n = 5 independent experiments). Statistical significance was assessed using two-tailed t-tests for two groups and one-way ANOVA with post hoc multiple comparisons test for multiple groups. *p < 0.05 vs Scr siRNA; Scr siRNA+VEGF; Ad-Cont+Vehicle or Ad-Cont+Scr siRNA. All values are mean ± S.D.