TRPP2 modulates ryanodine- and inositol-1,4,5-trisphosphate receptors-dependent Ca2+ signals in opposite ways in cerebral arteries

Abstract

TRPP2 is a cationic channel expressed in plasma membrane and in sarcoplasmic reticulum. In several cell lines, TRPP2 is described as a reticulum Ca(2+) leak channel but it also interacts with ryanodine and inositol 1,4,5-trisphosphate (InsP3) receptors to inhibit and increase the release of Ca(2+) stores, respectively. TRPP2 is known to be expressed in vascular smooth muscle cells, however its function in Ca(2+) signals remains poorly described in native cells, principally because the pharmacology is not developed. TRPP2 was expressed in cerebral arteries. Triptolide evoked Ca(2+) responses in a Ca(2+)-free solution as well as permeabilized arteries. This Ca(2+) signal was inhibited in presence of antisense oligonucleotide and siRNA directed against TRPP2 and antibody directed against the first loop of TRPP2. The partial inhibition of TRPP2 expression increased both the caffeine-evoked Ca(2+) responses and in vivo contraction. It also decreased the InsP3-evoked Ca(2+) responses. Finally, aging affected the regulations in which TRPP2 is engaged, whereas the triptolide-evoked Ca(2+) response was not modified. Taken together, our results have shown that TRPP2 is implicated in triptolide-induced Ca(2+) release from intracellular Ca(2+) stores. TRPP2 functionally interacts with both ryanodine and InsP3 receptors. These interactions were not similar in adult and old mice.

Keywords: Aging; Calcium signaling; Ryanodine receptor; TRPP2; Triptolide.