A GTP-binding protein modulates a Ca2+ pump present in reticulocyte endocytic vesicles.
Rat reticulocytes were used to prepare endocytic vesicles to study calcium fluxes across the endosomal membrane. We used 45Ca2+, and found that endocytic vesicles from reticulocytes present a Ca(2+)-ATPase that pumps Ca2+ into the lumen of vesicles. This activity was sensitive to vanadate and the calmodulin antagonists: trifluoperazine and calmidazolium. Western blot analysis using a monoclonal antibody evidenced that Ca(2+)-ATPase present in reticulocyte endocytic vesicles is probably the same as the erythrocyte Ca2+ pump. Ca2+ pump activity was shown to be partially inhibited by GTP gamma S. Moreover, mastoparan and benzalkonium chloride, both activators of heterotrimeric G proteins, were found to decrease 45Ca2+ uptake by endocytic vesicles. These results suggest the involvement of a trimeric G protein in the modulation of Ca(2+)-ATPase.
Vidal
M
M
URA 1856 CNRS, Université Montpellier II, France.
Lefevre
F
F
Rouot
B
B
Sainte-Marie
J
J
Philippot
J
J
D000818:Animals; D001548:Benzalkonium Compounds / Q000494:pharmacology; D015153:Blotting, Western; D002118:Calcium / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D051381:Rats; D017207:Rats, Sprague-Dawley; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology; D014862:Wasp Venoms / Q000494:pharmacology
D001548:Benzalkonium Compounds; D002147:Calmodulin; D004791:Enzyme Inhibitors; D007093:Imidazoles; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014862:Wasp Venoms; D014268:Trifluoperazine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D014638:Vanadates; C031938:calmidazolium; C037500:mastoparan; D019204:GTP-Binding Proteins; D000252:Calcium-Transporting ATPases; D002118:Calcium