An Elevation in Physical Coupling of Type 1 Inositol 1,4,5-Trisphosphate (IP 3 ) Receptors to Transient Receptor Potential 3 (TRPC3) Channels Constricts Mesenteric Arteries in Genetic Hypertension

Abstract

Hypertension is associated with an elevation in agonist-induced vasoconstriction, but mechanisms involved require further investigation. Many vasoconstrictors bind to phospholipase C–coupled receptors, leading to an elevation in inositol 1,4,5-trisphosphate (IP 3 ) that activates sarcoplasmic reticulum IP 3 receptors. In cerebral artery myocytes, IP 3 receptors release sarcoplasmic reticulum Ca 2+ and can physically couple to canonical transient receptor potential 3 (TRPC3) channels in a caveolin-1-containing macromolecular complex, leading to cation current activation that stimulates vasoconstriction. Here, we investigated mechanisms by which IP 3 receptors control vascular contractility in systemic arteries and IP 3 R involvement in elevated agonist-induced vasoconstriction during hypertension. Total and plasma membrane-localized TRPC3 protein was ≈2.7- and 2-fold higher in mesenteric arteries of spontaneously hypertensive rats (SHRs) than in Wistar-Kyoto (WKY) rat controls, respectively. In contrast, IP 3 R1, TRPC1, TRPC6, and caveolin-1 expression was similar. TRPC3 expression was also similar in arteries of pre-SHRs and WKY rats. Control, IP 3 -induced and endothelin-1 (ET-1)-induced fluorescence resonance energy transfer between IP3R1 and TRPC3 was higher in SHR than WKY myocytes. IP3-induced cation current was ≈3-fold larger in SHR myocytes. Pyr3, a selective TRPC3 channel blocker, and calmodulin and IP 3 receptor binding domain peptide, an IP 3 R-TRP physical coupling inhibitor, reduced IP 3 -induced cation current and ET-1–induced vasoconstriction more in SHR than WKY myocytes and arteries. Thapsigargin, a sarcoplasmic reticulum Ca 2+ -ATPase blocker, did not alter ET-1–stimulated vasoconstriction in SHR or WKY arteries. These data indicate that ET-1 stimulates physical coupling of IP 3 R1 to TRPC3 channels in mesenteric artery myocytes, leading to vasoconstriction. Furthermore, an elevation in IP 3 R1 to TRPC3 channel molecular coupling augments ET-1–induced vasoconstriction during hypertension.