Activation of TRPC6 calcium channels by diacylglycerol (DAG)-containing arachidonic acid: a comparative study with DAG-containing docosahexaenoic acid.
We synthesized a diacylglycerol (DAG)-containing arachidonic acid, i.e., 1-stearoyl-2-arachidonyl-sn-glycerol (SAG), and studied its implication in the modulation of canonical transient receptor potential sub-type 6 (TRPC6) channels in stably-transfected HEK-293 cells. SAG induced the influx of Ca(2+), and also of other bivalent cations like Ba(2+) and Sr(2+), in these cells. SAG-evoked Ca(2+) influx was not due to its metabolites as inhibitors of DAG-lipase (RHC80267) and DAG-kinase (R50922) failed to inhibit the response of the same. To emphasise that SAG exerts its action via its DAG configuration, but not due to the presence of stearic acid at sn-1 position, we synthesized 1-palmitoyl-2-arachidonyl-sn-glycerol (PAG). PAG-induced increases in [Ca(2+)](i) were not significantly different from those induced by SAG. For the comparative studies, we also synthesized the DAG-containing docosahexaenoic acid, i.e., 1-stearoyl-2-docosahexaenoyl-sn-glycerol (SDG). We observed that SDG and 1,2-dioctanoyl-sn-glycerol (DOG), a DAG analogue, also evoked increases in [Ca(2+)](i), which were lesser than those evoked by SAG. However, activation of TRPC6 channels by all the DAG molecular species (SAG, DOG and SDG) required Src kinases as the tyrosine kinase inhibitors, PP2 and SU6656, significantly attenuated the increases in [Ca(2+)](i) evoked by these agents. Moreover, disruption of lipid rafts with methyl-beta-cyclodextrin completely abolished SAG-, DOG- and SDG-induced increases in [Ca(2+)](i). The present study shows that SAG as well as SDG and DOG stimulate Ca(2+) influx through the activation of TRPC6 calcium channels which are regulated by Src kinases and intact lipid raft domains.
Aires
Virginie
V
Département de Physiologie, UPRES Lipides and Nutrition, Université de Bourgogne, Faculté des Sciences de la Vie, 6 Boulevard Gabriel, 2100 Dijon, France.
Hichami
Aziz
A
Boulay
Guylain
G
Khan
Naim Akhtar
NA
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004075:Diglycerides / Q000138:chemical synthesis / Q000494:pharmacology*; D004281:Docosahexaenoic Acids / Q000138:chemical synthesis / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D050052:TRPC Cation Channels / Q000378:metabolism*; D000074287:TRPC6 Cation Channel; D019061:src-Family Kinases / Q000378:metabolism
C524616:1-stearoyl-2-docosahexaenoylglycerol; D004075:Diglycerides; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C492146:Trpc6 protein, mouse; D004281:Docosahexaenoic Acids; C075809:1-stearoyl-2-arachidonoylglycerol; D019061:src-Family Kinases; D002118:Calcium