Phenylarsine oxide increases intracellular calcium mobility and inhibits Ca(2+)-dependent ATPase activity in thymocytes.
A rise in intracellular Ca(2+) levels has been implicated as a regulatory signal for the initiation of lymphocyte proliferation. In the present study the mechanism underlying the elevation of [Ca(2+)] induced by phenylarsine oxide [PAO] was investigated in thymocytes. This agent inhibits HIV-1 replication and also NF-kappaB-mediated activation. It has been reported that the PAO-induced Ca(2+) elevation results from an enhanced plasma membrane calcium permeability in T cells. Here, we present biochemical evidence that the PAO-induced Ca(2+) increase was independent of external Ca(2+). Consistent with these facts, when [Ca(2+)](i) was depleted by prolonged incubation of the cells in Ca(2+)-free medium, PAO addition did not lead to [Ca(2+)](i) increase. These data indicate the involvement of intracellular organelles of thymocytes as the source of Ca(2+). Moreover, evidence is presented that PAO inhibited Ca(2+)-dependent ATPase activity from thymocytes and sarcoplasmic reticulum from skeletal muscle. This inhibition was dose-dependent, with a IC(50) of about 30 microM for both preparations of enzyme. The ability of PAO to inhibit Ca(2+)-dependent ATPase represents a novel mechanism of action for this drug. Present data suggest that the PAO-dependent [Ca(2+)](i) increase could be mainly the result of inhibition of Ca(2+)-dependent ATPase. In addition, we describe also a Ca(2+)-dependence for PAO effect on tyrosine phosphorylation.
Hmadcha
A
A
Facultad de Medicina, Universidad de Sevilla, Seville, 41009, USA.
Carballo
M
M
Conde
M
M
Márquez
G
G
Monteseirín
J
J
Martin-Nieto
J
J
Bedoya
F J
FJ
Pintado
E
E
Sobrino
F
F
D000818:Animals; D001152:Arsenicals / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015497:HIV-1 / Q000187:drug effects / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D051379:Mice; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D015388:Organelles / Q000187:drug effects / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D014779:Virus Replication / Q000187:drug effects
D001152:Arsenicals; D004791:Enzyme Inhibitors; C029341:oxophenylarsine; D000252:Calcium-Transporting ATPases; D002118:Calcium