Protein interactions on the erythrocyte membrane: Dynamic and structural aspects

Seon Hee Chang, Purdue University

Abstract

The band 3-ankyrin-spectrin bridge and the glycophorin C-protein 4.1-spectrin/actin bridge constitute the two major tethers between the erythrocyte membrane and its spectrin skeleton. We report here that elevation of cytosolic 2,3-bisphosphoglycerate, an increase in intracellular Ca2+, removal of cell O2, a decrease in intracellular pH, and activation of erythrocyte protein kinase C all promote dissociation of protein 4.1 from glycophorin C, leading to reduced retention of glycophorin C in detergent-extracted spectrin/actin skeletons. Significantly, dissociation of glycophorin C from the membrane skeletons does not impact membrane deformability, stability or whole cell filterability. A critical ankyrin binding site on cdb3 was identified by crystal structure analysis and site-directed mutagenesis. We have presented evidence that the β-hairpin loop comprising residues 175–185 of cdb3 constitutes a major ankyrin binding site on the erythrocyte membrane. Deletion mutagenesis of the NH 2-terminus of cdb3 further demonstrated that the first 50 residues of the polypeptide are not directly involved in ankyrin binding. Dematin is an actin binding protein in the erythrocyte membrane. We demonstrate the critical importance of the headpiece domain of dematin in the maintenance of mechanical properties of erythrocytes in vivo. The substrates for μ-calpain are components of the erythrocyte membrane skeleton. We document the effect of a complete μ-calpain deficiency in the membrane mechanical properties of mouse erythrocytes. Erythrocytes from two hydrocytosis patients were studied to gain potential insight into the mechanism of thrombosis in this disorder. The percentage of hydrocytosis erythrocytes with phosphatidylserine exposed on the outer surfaces was increased in both patients.

Degree

Ph.D.

Advisors

Low, Purdue University.

Subject Area

Biochemistry

COinS