A GTP-binding protein modulates a Ca2+ pump present in reticulocyte endocytic vesicles

Biochem Mol Biol Int. 1995 Apr;35(4):889-98.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzalkonium Compounds / pharmacology
  • Blotting, Western
  • Calcium / antagonists & inhibitors
  • Calcium / pharmacokinetics
  • Calcium-Transporting ATPases / antagonists & inhibitors
  • Calcium-Transporting ATPases / drug effects
  • Calcium-Transporting ATPases / metabolism*
  • Calmodulin / antagonists & inhibitors
  • Calmodulin / pharmacology
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Dose-Response Relationship, Drug
  • Electrophoresis, Polyacrylamide Gel
  • Endocytosis / drug effects
  • Endocytosis / physiology*
  • Endosomes / drug effects
  • Endosomes / metabolism*
  • Enzyme Inhibitors / pharmacology
  • Erythrocytes / drug effects
  • Erythrocytes / metabolism
  • GTP-Binding Proteins / drug effects
  • GTP-Binding Proteins / metabolism*
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Imidazoles / pharmacology
  • Intercellular Signaling Peptides and Proteins
  • Peptides
  • Rats
  • Rats, Sprague-Dawley
  • Reticulocytes / drug effects
  • Reticulocytes / metabolism*
  • Trifluoperazine / pharmacology
  • Vanadates / pharmacology
  • Wasp Venoms / pharmacology

Substances

  • Benzalkonium Compounds
  • Calmodulin
  • Enzyme Inhibitors
  • Imidazoles
  • Intercellular Signaling Peptides and Proteins
  • Peptides
  • Wasp Venoms
  • Trifluoperazine
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Vanadates
  • calmidazolium
  • mastoparan
  • GTP-Binding Proteins
  • Calcium-Transporting ATPases
  • Calcium