ERp44 C160S/C212S mutants regulate IP3R1 channel activity

摘要

Previous studies have indicated that ERp44 inhibits inositol 1,4,5-trisphosphate (IP₃)-induced Ca^{2+ release (IICR) via IP₃R₁, but the mechanism remains largely unexplored. Using extracellular ATP to induce intracellular calcium transient as an IICR model, Ca2+ image, pull down assay, and Western blotting experiments were carried out in the present study. We found that extracellular ATP induced calcium transient via IP₃Rs (IICR) and the IICR were markedly decreased in ERp44 overexpressed Hela cells. The inhibitory effect of C160S/C212S but not C29S/T396A/ΔT(331–377) mutants of ERp44 on IICR were significantly decreased compared with ERp44. However, the binding capacity of ERp44 to L3V domain of IP₃R₁ (1L3V) was enhanced by ERp44 C160S/C212S mutation. Taken together, these results suggest that the mutants of ERp44, C160/C212, can more tightly bind to IP₃R₁ but exhibit a weak inhibition of IP₃R₁ channel activity in Hela cells.}