Heterotrimeric G protein Gi is involved in a signal transduction pathway for ATP release from erythrocytes.

Am J Physiol Heart Circ Physiol

Dept. of Pharmacological and Physiological Science, St. Louis Univ. School of Medicine, M-208, St. Louis, MO 63104, USA.

Published: March 2004

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Erythrocytes are reported to release ATP in response to mechanical deformation and decreased oxygen tension. Previously we proposed that receptor-mediated activation of the heterotrimeric G protein G(s) resulted in ATP release from erythrocytes. Here we investigate the hypothesis that activation of heterotrimeric G proteins of the G(i) subtype are also involved in a signal transduction pathway for ATP release from rabbit erythrocytes. Heterotrimeric G proteins G(alphai1), G(alphai2), and G(alphai3) but not G(alphao) were identified in rabbit and human erythrocyte membranes. Pretreatment of rabbit erythrocytes with pertussis toxin (100 ng/ml, 2 h), which uncouples G(i/o) from their effector proteins, inhibited deformation-induced ATP release. Incubation of rabbit and human erythrocytes with mastoparan (Mas, 10 microM) or Mas-7 (1 microM), which are compounds that directly activate G(i) proteins, resulted in ATP release. However, rabbit erythrocytes did not release ATP when incubated with Mas-17 (10 microM), which is an inactive Mas analog. In separate experiments, Mas (10 microM) but not Mas-17 (10 microM) increased intracellular concentrations of cAMP when incubated with rabbit erythrocytes. Importantly, Mas-induced ATP release from rabbit erythrocytes was inhibited after treatment with pertussis toxin (100 ng/ml, 2 h). These data are consistent with the hypothesis that the heterotrimeric G protein G(i) is a component of a signal transduction pathway for ATP release from erythrocytes.

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http://dx.doi.org/10.1152/ajpheart.00677.2003DOI Listing

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