TRPC1 regulates calcium‐activated chloride channels in salivary gland cells

Abstract

Calcium‐activated chloride channel (CaCC) plays an important role in modulating epithelial secretion. It has been suggested that in salivary tissues, sustained fluid secretion is dependent on Ca2+ influx that activates ion channels such as CaCC to initiate Cl− efflux. However direct evidence as well as the molecular identity of the Ca2+ channel responsible for activating CaCC in salivary tissues is not yet identified. Here we provide evidence that in human salivary cells, an outward rectifying Cl− current was activated by increasing [Ca2+]i, which was inhibited by the addition of pharmacological agents niflumic acid (NFA), an antagonist of CaCC, or T16Ainh‐A01, a specific TMEM16a inhibitor. Addition of thapsigargin (Tg), that induces store‐depletion and activates TRPC1‐mediated Ca2+ entry, potentiated the Cl− current, which was inhibited by the addition of a non‐specific TRPC channel blocker SKF96365 or removal of external Ca2+. Stimulation with Tg also increased plasma membrane expression of TMEM16a protein, which was also dependent on Ca2+ entry. Importantly, in salivary cells, TRPC1 silencing, but not that of TRPC3, inhibited CaCC especially upon store depletion. Moreover, primary acinar cells isolated from submandibular gland also showed outward rectifying Cl− currents upon increasing [Ca2+]i. These Cl− currents were again potentiated with the addition of Tg, but inhibited in the presence of T16Ainh‐A01. Finally, acinar cells isolated from the submandibular glands of TRPC1 knockout mice showed significant inhibition of the outward Cl− currents without decreasing TMEM16a expression. Together the data suggests that Ca2+ entry via the TRPC1 channels is essential for the activation of CaCC. J. Cell. Physiol. 9999: 2848–2856, 2015. © 2015 Wiley Periodicals, Inc.

TRPC1 expression and function inhibit ER stress and cell death in salivary gland cells

“…Data presented thus far indicate that loss of TRPC1 in salivary gland cells lead to ER stress that could account for the loss of salivary gland cells. Thus, to understand the physiological relevance of the TRPC1 channel in ER stress and salivary gland function, we used control and TRPC1 knockout mice . Mice‐lacking TRPC1 expression showed a significant increase in ER stress markers and expression of GRP94, Ero1α, and CHOP were significantly increased in TRPC1 knockout mice, when compared with age‐matched wild‐type control mice (Figure A,B).…”

“…Thus, to understand the physiological relevance of the TRPC1 channel in ER stress and salivary gland function, we used control and TRPC1 knockout mice. 24,29 Mice-lacking TRPC1 expression showed a significant increase in ER stress markers and expression of GRP94, Ero1α, and CHOP were significantly increased in TRPC1 knockout mice, when compared with age-matched wild-type control mice (Figure 5A,B). Consistent to the results presented above increased caspase 3 expression as well as increased Tunnel staining was observed in TRPC1 knockout mice.…”

TRPC1, Orai1, and STIM1 in SOCE: Friends in tight spaces

“…Acinar cells from salivary glands and pancreas, and aortic endothelial cells exhibit dramatically attenuated SOCE with corresponding reduction in Ca 2+ -dependent processes such as the activation of K Ca and Cl − channels. Importantly, agonist-stimulated fluid and protein secretion from the salivary glands and pancreas, respectively, as well as vasorelaxation of the aorta, are adversely impacted [26–28, 40–42]. It is worth noting that the residual Orai1 cannot compensate for the loss of TRPC1 function in these cells, which clearly establishes the non-redundancy of TRPC1.…”

The Effect and Mechanism of TRPC1, 3, and 6 on the Proliferation, Migration, and Lumen Formation of Retinal Vascular Endothelial Cells Induced by High Glucose

“…Therefore, further in vivo experiments are needed to construct relevant animal models and to further explore the correlation between TRPC and retinal neovascularization and its possible mechanisms. Since SKF96365 is a nonspecific inhibitor of the TRPC pathway [50], it is unclear which subtypes are involved in angiogenesis, and there are many unknown areas in blocking TRPCs. The regulation between factors is complex, and TRPC may not only participate.…”