[8-(Diethylamino)octyl-3,4,5-trimethoxybenzoate, HCl], the inhibitor of intracellular calcium mobilization, blocked mitogen-induced T cell proliferation by interfering with the sustained phase of protein kinase C activation.
The physiological role of IP(3)-dependent Ca(2+) release in T cell activation was in question due to the contradictory findings that [8-(Diethylamino)octyl-3,4,5-trimethoxybenzoate, HCl] (TMB-8), an inhibitor of intracellular Ca(2+) mobilization, blocked T cell proliferation, curtailing specifically the level of released Ca(2+) did not affect T cell activation and T cell line lacking IP(3) receptor was defective in IL-2 production in response to TCR/CD3 ligand. In the present study we found that TMB-8 inhibited Concanavalin A (Con A)- but not PMA/Ionomycin-induced T cell proliferation in a reversible and dose-dependent manner. The kinetic study revealed that TMB-8 exerted the inhibitory effect at a very early step of T cell activation. The Ca(2+) ionophore ionomycin augmented instead of overcoming the inhibitory effect of TMB-8, although the same doses of ionomycin alone had no effect on Con A-induced T cell proliferation. PMA the metabolically stable, but not diacylglycerol (DAG) the metabolically labile, activator of protein Kinase C (PKC) completely overcome the antiproliferative effect of TMB-8. A specific DAG lipase inhibitor RHC80267 also overcome the effect of TMB-8. Taken together, these results showed that the process of Ca(2+) release through IP(3) receptor, not the released Ca(2+), is essential for the sustained phase of PKC activation during T cell proliferation.
Kumar
S
S
Molecular Biology Unit, Institute of Medical Sciences, Banaras Hindu University, Varanasi-221005, India.
Chakrabarti
R
R
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects*; D003208:Concanavalin A / Q000494:pharmacology; D003512:Cyclohexanones / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D015759:Ionomycin / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D003512:Cyclohexanones; D004075:Diglycerides; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009281:Naphthalenes; D018160:Receptors, Cytoplasmic and Nuclear; D003208:Concanavalin A; D015759:Ionomycin; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; C036535:1,6-bis(cyclohexyloximinocarbonyl)hexane; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium