Regulation of Ca V 3.1 T‐type Ca 2+ channel expression by cAMP in pulmonary microvascular endothelial cells.

Abstract

Activation of CaV3.1 T-type Ca2+ channel contributes to Gq-linked agonist-induced and store-operated Ca2+ entry in pulmonary microvascular endothelial cells (PMVECs). Since cAMP-dependent pathways have been implicated in upregulation of ion channels including voltage-gated Ca2+ channels in excitable cells, we sought to examine whether a sustained elevation of cAMP increases the synthesis of CaV3.1 channels in endothelial cells. Cultured rat PMVECs were exposed to exogenous cAMP (pCPT-cAMP 200 μM) for up to 96 hr and then subjected to whole-cell patch-clamp recordings to assess macroscopic T-type currents. Using a two-step voltage protocol to detect the maximally evoked tail current, we observed that exposure of exogenous cAMP did not have an immediate effect on the T-type current, whereas long-term exposure (> 24 hr) markedly increased the occurrence of high T-type current in PMVECs. The increased T-type current displayed virtually identical activation and inactivation properties as the original T-type current, and correlated with an elevated mRNA level after 24 hr exposure to exogenous cAMP. Further, we revealed that 8CPT-2Me-cAMP, a selective cAMP-regulated guanine nucleotide exchange factor (Epac) agonist, did not reproduce the effect of pCPT-cAMP on T-type current, while PKA inhibitor H89 and Rp-cAMPS, a competitive antagonist of cAMP binding to PKA, prevented the action of pCPT-cAMP. Together, these results support the idea that PKA-dependent signaling pathways are involved in up-regulation of CaV3.1 T-type Ca2+ channels in pulmonary microvascular endothelial cells. Supported by HL074116