Orai1 and TRPC1 Proteins Co-localize with CaV1.2 Channels to Form a Signal Complex in Vascular Smooth Muscle Cells

Abstract

Voltage-dependent Ca1.2 L-type Ca channels (LTCC) are the main route for calcium entry in vascular smooth muscle cells (VSMC). Several studies have also determined the relevant role of store-operated Ca channels (SOCC) in vascular tone regulation. Nevertheless, the role of Orai1- and TRPC1-dependent SOCC in vascular tone regulation and their possible interaction with Ca1.2 are still unknown. The current study sought to characterize the co-activation of SOCC and LTCC upon stimulation by agonists, and to determine the possible crosstalk between Orai1, TRPC1, and Ca1.2. Aorta rings and isolated VSMC obtained from wild type or smooth muscle-selective conditional Ca1.2 knock-out (Ca1.2) mice were used to study vascular contractility, intracellular Ca mobilization, and distribution of ion channels. We found that serotonin (5-HT) or store depletion with thapsigargin (TG) enhanced intracellular free Ca concentration ([Ca]) and stimulated aorta contraction. These responses were sensitive to LTCC and SOCC inhibitors. Also, 5-HT- and TG-induced responses were significantly attenuated in Ca1.2 mice. Furthermore, hyperpolarization induced with cromakalim or valinomycin significantly reduced both 5-HT and TG responses, whereas these responses were enhanced with LTCC agonist Bay-K-8644. Interestingly, in situ proximity ligation assay revealed that Ca1.2 interacts with Orai1 and TRPC1 in untreated VSMC. These interactions enhanced significantly after stimulation of cells with 5-HT and TG. Therefore, these data indicate for the first time a functional interaction between Orai1, TRPC1, and Ca1.2 channels in VSMC, confirming that upon agonist stimulation, vessel contraction involves Ca entry due to co-activation of Orai1- and TRPC1-dependent SOCC and LTCC.

Store-Operated Calcium Entries Control Neural Stem Cell Self-Renewal in the Adult Brain Subventricular Zone

“…Our study not only confirms the existence of SOCE in SVZ cells, but also shows that in addition to Orai1, SVZ cells also possess TRPC1, as do embryonic brain stem cells from which adult NSC derive . In addition to supporting calcium entries, SOC have been shown to activate voltage‐gated channels in vascular cells . A previous electrophysiological study and our recordings (data not shown) indicate that SVZ stem cells are highly polarized and fail to produce action potentials.…”

TRPC Channels in the SOCE Scenario

“…A well-known depolarizing TRP channel is TRPM4, which has been found to depolarize T lymphocytes [95]. Membrane depolarization induced by TRPC channel gating has been associated to a functional activation of voltage-dependent Ca 2+ channels in electrically excitable cells [96,97]. In addition, depolarization evoked by Ca 2+ and Na + influx through TRPC channels leads to subsequent attenuation of the driving force for Ca 2+ entry via Orai1 channels.…”

Effect of Docosahexaenoic Acid on Voltage-Independent Ca²⁺ Entry Pathways in Cultured Vascular Smooth Muscle Cells Stimulated with 5-Hydroxytryptamine

“…Kwan et al 18) reported that TRPC1 and BK Ca colocalize in VSMCs, and Ca 2+ influx through TRPC1 activates BK Ca to induce membrane hyperpolarization. Ávila-Medina et al 19) reported that TRPC1 and Orai1 co-localize with voltage-dependent Ca V 1.2 L-type Ca 2+ channels, and 5-HTinduced TRPC1-dependent SOCE can trigger the activation of voltage-dependent Ca V 1.2 L-type Ca 2+ channels. Therefore, it might still be worthwhile continuing to determine the effect of DHA on TRPC1 function in VSMCs.…”