Diacylglycerol activates the influx of extracellular cations in T-lymphocytes independently of intracellular calcium-store depletion and possibly involving endogenous TRP6 gene products.
In Jurkat and human peripheral blood T-lymphocytes, 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane-permeant analogue of diacylglycerol, activated the influx of Ca(2+), Ba(2+) and Sr(2+). OAG also caused plasma-membrane depolarization in Ca(2+)-free media that was recovered by the addition of bivalent cation, indicating the activation of Na(+) influx. OAG-induced cation influx was (i) mimicked by the natural dacylglycerol 1-stearoyl-2-arachidonyl-sn-glycerol, (ii) not blocked by inhibiting protein kinase C or in the absence of phospholipase C activity and (iii) blocked by La(3+) and Gd(3+). Differently from OAG, both thapsigargin and phytohaemagglutinin activated a potent influx of Ca(2+), but little influx of Ba(2+) and Sr(2+). Moreover, the influx of Ca(2+) activated by thapsigargin and that activated by OAG were additive. Furthermore, several drugs (i.e. econazole, SKF96365, carbonyl cyanide p-trifluoromethoxyphenylhydrazone, 2-aminoethoxy diphenylborate and calyculin-A), while inhibiting the influx of Ca(2+) induced by both thapsigargin and phytohaemagglutinin, did not affect OAG-stimulated cation influx. Transient receptor potential (TRP) 3 and TRP6 proteins have been shown previously to be activated by diacylglycerol when expressed heterologously in animal cells [Hofmann, Obukhov, Schaefer, Harteneck, Gudermann and Schultz (1999) Nature (London) 397, 259-263]. In both Jurkat and peripheral blood T-lymphocytes, mRNA encoding TRP proteins 1, 3, 4 and 6 was detected by reverse transcriptase PCR, and the TRP6 protein was detected by Western blotting in a purified plasma-membrane fraction. We conclude that T-cells express a diacylglycerol-activated cation channel, unrelated to the channel involved in capacitative Ca(2+) entry, and associated with the expression of TRP6 protein.
Gamberucci
Alessandra
A
Dipartimento di Fisiopatologia e Medicina Sperimentale, Università di Siena, Viale A. Moro no. 1, 53100-Siena, Italy.
Giurisato
Emanuele
E
Pizzo
Paola
P
Tassi
Maristella
M
Giunti
Roberta
R
McIntosh
Deirdre Patricia
DP
Benedetti
Angelo
A
D001464:Barium / Q000378:metabolism; D015153:Blotting, Western; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D002412:Cations; D002460:Cell Line; D004075:Diglycerides / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D019169:Jurkat Cells; D008564:Membrane Potentials; D010835:Phytohemagglutinins / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013324:Strontium / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*; D050052:TRPC Cation Channels; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
D001896:Boron Compounds; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002412:Cations; D004075:Diglycerides; D004791:Enzyme Inhibitors; D007093:Imidazoles; D010835:Phytohemagglutinins; D012333:RNA, Messenger; D050052:TRPC Cation Channels; D001464:Barium; D019284:Thapsigargin; C109986:2-aminoethoxydiphenyl borate; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium; D013324:Strontium