Regulation of canonical transient receptor potential (TRPC) channel function by diacylglycerol and protein kinase C.
The mechanism of receptor-induced activation of the ubiquitously expressed family of mammalian canonical transient receptor potential (TRPC) channels has been the focus of intense study. Primarily responding to phospholipase C (PLC)-coupled receptors, the channels are reported to receive modulatory input from diacylglycerol, endoplasmic reticulum inositol 1,4,5-trisphosphate receptors and Ca2+ stores. Analysis of TRPC5 channels transfected within DT40 B cells and deletion mutants thereof revealed efficient activation in response to PLC-beta or PLC-gamma activation, which was independent of inositol 1,4,5-trisphoshate receptors or the content of stores. In both HEK293 cells and DT40 cells, TRPC5 and TRPC3 channel responses to PLC activation were highly analogous, but only TRPC3 and not TRPC5 channels responded to the addition of the permeant diacylglycerol (DAG) analogue, 1-oleoyl-2-acetyl-sn-glycerol (OAG). However, OAG application or elevated endogenous DAG, resulting from either DAG lipase or DAG kinase inhibition, completely prevented TRPC5 or TRPC4 activation. This inhibitory action of DAG on TRPC5 and TRPC4 channels was clearly mediated by protein kinase C (PKC), in distinction to the stimulatory action of DAG on TRPC3, which is established to be PKC-independent. PKC activation totally blocked TRPC3 channel activation in response to OAG, and the activation was restored by PKC-blockade. PKC inhibition resulted in decreased TRPC3 channel deactivation. Store-operated Ca2+ entry in response to PLC-coupled receptor activation was substantially reduced by OAG or DAG-lipase inhibition in a PKC-dependent manner. However, store-operated Ca2+ entry in response to the pump blocker, thapsigargin, was unaffected by PKC. The results reveal that each TRPC subtype is strongly inhibited by DAG-induced PKC activation, reflecting a likely universal feedback control on TRPCs, and that DAG-mediated PKC-independent activation of TRPC channels is highly subtype-specific. The profound yet distinct control by PKC and DAG of the activation of TRPC channel subtypes is likely the basis of a spectrum of regulatory phenotypes of expressed TRPC channels.
Venkatachalam
Kartik
K
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Zheng
Fei
F
Gill
Donald L
DL
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000172:deficiency / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D027682:Cation Transport Proteins; D002460:Cell Line; D002645:Chickens; D019852:Diacylglycerol Kinase / Q000037:antagonists & inhibitors; D004075:Diglycerides / Q000494:pharmacology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007473:Ion Channels / Q000235:genetics; D007527:Isoenzymes / Q000378:metabolism; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors; D051379:Mice; D054799:Phospholipase C beta; D051966:Phospholipase C gamma; D011493:Protein Kinase C / Q000378:metabolism*; D043642:Receptor, Muscarinic M5; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency / Q000502:physiology; D011976:Receptors, Muscarinic / Q000235:genetics; D050052:TRPC Cation Channels; D014162:Transfection; D010738:Type C Phospholipases / Q000172:deficiency / Q000378:metabolism / Q000502:physiology
D015220:Calcium Channels; D027682:Cation Transport Proteins; D004075:Diglycerides; D004791:Enzyme Inhibitors; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007473:Ion Channels; D007527:Isoenzymes; D043642:Receptor, Muscarinic M5; D018160:Receptors, Cytoplasmic and Nuclear; D011976:Receptors, Muscarinic; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; C491780:TRPC5 protein, human; C112021:Trpc5 protein, mouse; C038237:1-oleoyl-2-acetylglycerol; D019852:Diacylglycerol Kinase; D011493:Protein Kinase C; D008071:Lipoprotein Lipase; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D051966:Phospholipase C gamma; D002118:Calcium