Direct activation of human TRPC6 and TRPC3 channels by diacylglycerol

Abstract

Eukaryotic cells respond to many hormones and neurotransmitters with increased activity of the enzyme phospholipase C and a subsequent rise in the concentration of intracellular free calcium ([Ca2+]i). The increase in [Ca2+]i occurs as a result of the release of Ca2+ from intracellular stores and an influx of Ca2+ through the plasma membrane; this influx of Ca2+ may or may not be store-dependent. Drosophila transient receptor potential (TRP) proteins and some mammalian homologues (TRPC proteins) are thought to mediate capacitative Ca2+ entry. Here we describe the molecular mechanism of store-depletion-independent activation of a subfamily of mammalian TRPC channels. We find that hTRPC6 is a non-selective cation channel that is activated by diacylglycerol in a membrane-delimited fashion, independently of protein kinases C activated by diacylglycerol. Although hTRPC3, the closest structural relative of hTRPC6, is activated in the same way, TRPCs 1, 4 and 5 and the vanilloid receptor subtype 1 are unresponsive to the lipid mediator. Thus, hTRPC3 and hTRPC6 represent the first members of a new functional family of second-messenger-operated cation channels, which are activated by diacylglycerol.

Thapsigargin activates Ca2+ entry both by store-dependent, STIM1/Orai1-mediated, and store-independent, TRPC3/PLC/PKC-mediated pathways in human endothelial cells

“…The precise mechanism between PKC activation and TRPC3 opening remains however to be firmly established, but our data suggested that Src is, at least partially, involved in this process. Considering that the inhibition of the Ca 2+ entry varied between about 40 and 60% upon src inhibition or siRNA treatment against PKC , it is possible that for a part, TRPC3 is also getting directly activated by DAG, like it was already reported [15,63,64]. This point, however, remains to be further investigated.…”

“…When exogenously expressed some TRPC channels displayed SOCE activity [12][13][14]. However, numerous studies also demonstrated that TRPC channels did not operate as SOCE channels, but rather are gated by second messengers like Ca 2+ or diacylglycerol (DAG; [15][16][17]). Hence, the involvement of TRPC channels in the SOCE mechanism is a controversial issue, and appears to dependent on the cell types investigated, and importantly on the expression level of the TRPC [14,18,19].…”

The role of TRPC6 in HGF-induced cell proliferation of human prostate cancer DU145 and PC3 cells

“…Because TRPC6 channels can be activated by diacylglycerol (DAG) [20], we used OAG, a membranepermeable analogue of DAG, to test Ca 2+ inflow in cells.…”

Activation of phospholipase D activity in transforming growth factor-beta-induced cell growth inhibition

“…In our studies, no effect of TGF-on the fetal calf serum-, EGF-, and PMA-induced activation of PLD was observed. Effects of TGF-1 on the PC-and PIPs-derived DAG formation Altered PLD activity could influence the level of intracellular second messenger DAG, which is formed through PA phosphatase-catalyzed hydrolysis of PA. DAG plays an important role in cellular growth and other functions, which acts as a physiological activator for some PKC isoforms [26] and has been shown to be a direct Ca 2+ ion channel regulator [27]. Though it has been reported that PC-PLC are involved in the TGF-1 -mediated signaling or growth inhibition [28], [29], the effects of TGF-on the phospholipase activity and the DAG production has not been determined.…”