Blunted apoptosis of erythrocytes in mice deficient in the heterotrimeric G-protein subunit Gαi2

Rosi Bissinger,Mehrdad Ghashghaeinia,Andreas F Mack,Elisabeth Lang,Birgit Fehrenbacher,Sabina Honisch,Martin Schaller,Anja T Umbach,Hajar Fakhri,Christine Zelenak,Rexhep Rexhepaj,Florian Lang,Hong Chen,Yogesh Singh,Syed M Qadri,Guilai Liu,Lutz Birnbaumer,Guoxing Liu,Adrian Lupescu

doi:10.1038/srep30925

Abstract

Putative functions of the heterotrimeric G-protein subunit Gαi2-dependent signaling include ion channel regulation, cell differentiation, proliferation and apoptosis. Erythrocytes may, similar to apoptosis of nucleated cells, undergo eryptosis, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine (PS) exposure. Eryptosis may be triggered by increased cytosolic Ca2+ activity and ceramide. In the present study, we show that Gαi2 is expressed in both murine and human erythrocytes and further examined the survival of erythrocytes drawn from Gαi2-deficient mice (Gαi2−/−) and corresponding wild-type mice (Gαi2+/+). Our data show that plasma erythropoietin levels, erythrocyte maturation markers, erythrocyte counts, hematocrit and hemoglobin concentration were similar in Gαi2−/− and Gαi2+/+ mice but the mean corpuscular volume was significantly larger in Gαi2−/− mice. Spontaneous PS exposure of circulating Gαi2−/− erythrocytes was significantly lower than that of circulating Gαi2+/+ erythrocytes. PS exposure was significantly lower in Gαi2−/− than in Gαi2+/+ erythrocytes following ex vivo exposure to hyperosmotic shock, bacterial sphingomyelinase or C6 ceramide. Erythrocyte Gαi2 deficiency further attenuated hyperosmotic shock-induced increase of cytosolic Ca2+ activity and cell shrinkage. Moreover, Gαi2−/− erythrocytes were more resistant to osmosensitive hemolysis as compared to Gαi2+/+ erythrocytes. In conclusion, Gαi2 deficiency in erythrocytes confers partial protection against suicidal cell death.

Highlights

May-Grünwald staining further revealed no apparent changes in erythrocyte shape from Gαi2−/− mice as compared to erythrocytes from Gαi2+/+ mice (Fig. 1B)
The present observations disclose the expression of Gαi[2] in human and murine erythrocytes and further reveals that Gαi[2] deficiency confers partial protection against suicidal erythrocyte death or eryptosis
Our findings show that the percentage of eryptotic cells in circulating blood is significantly lower in Gαi2−/− mice as in Gαi2+/+ mice

Summary

Introduction

Erythrocytes may undergo suicidal death or eryptosis[19,20], which, similar to apoptosis, is triggered by osmotic shock and characterized by cell shrinkage and cell membrane scrambling[20,21]. Eryptosis may be triggered by activation of Ca2+-permeable cation channels[20] which subsequently leads to increase of cytosolic Ca2+. The cation channels are activated by prostaglandin E2, which is formed following exposure of erythrocytes to hyperosmotic shock[19]. In the present study we explored whether the Gαi[2] isoform is expressed in erythrocytes and whether it participates in the regulation of erythrocyte survival To this end, eryptosis was determined in erythrocytes from Gαi[2] knockout mice (Gαi2−/−) and their wild type littermates (Gαi2+/+)

Methods

Results

Conclusion