title: Modulation of erythrocyte membrane mechanical function by protein 4.1 phosphorylation.
abstract: Erythrocyte membrane mechanical function is regulated by the spectrin-based membrane skeleton composed of alpha- and beta-spectrin, actin, protein 4.1R (4.1R), and adducin. Post-translational modifications of these proteins have been suggested to modulate membrane mechanical function. Indeed, beta-spectrin phosphorylation by casein kinase I has been shown to decrease membrane mechanical stability. However, the effects of the phosphorylation of skeletal proteins by protein kinase C (PKC), a serine/threonine kinase, have not been elucidated. In the present study, we explored the functional consequences of the phosphorylation of 4.1R and adducin by PKC. We identified Ser-312 in 4.1R as the PKC phosphorylation site. Using antibodies raised against phosphopeptides of 4.1R and adducin, we documented significant differences in the time course of phosphorylation of adducin and 4.1R by PKC. Although adducin was phosphorylated rapidly by the activation of membrane-bound atypical PKC by phorbol 12-myristate 13-acetate stimulation, there was a significant delay in the phosphorylation of 4.1R because of delayed recruitment of conventional PKC from cytosol to the membrane. This differential time course in the phosphorylation of 4.1R and adducin in conjunction with membrane mechanical stability measurements enabled us to document that, although phosphorylation of adducin by PKC has little effect on membrane mechanical stability, additional phosphorylation of 4.1R results in a marked decrease in membrane mechanical stability. We further showed that the phosphorylation of 4.1R by PKC results in its decreased ability to form a ternary complex with spectrin and actin as well as dissociation of glycophorin C from the membrane skeleton. These findings have enabled us to define a regulatory role for 4.1R phosphorylation in dynamic regulation of red cell membrane properties.
authors.affiliation: Department of Biochemistry, Tokyo Women's Medical University, 8-1 Kawada-Cho, Shinjuku-Ku, Tokyo 162-8666, Japan.
authors.forename: Sumie
authors.initials: S
authors.lastname: Manno
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Takakuwa
authors.forename: Narla
authors.initials: N
authors.lastname: Mohandas
mesh_terms: D000199:Actins / Q000737:chemistry; D001665:Binding Sites; D001798:Blood Proteins / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000737:chemistry; D047389:Casein Kinase I / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003598:Cytoskeletal Proteins; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D012694:Serine / Q000737:chemistry; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013049:Spectrin / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D000099291:Adducins
chemical_list: D000199:Actins; D001798:Blood Proteins; D002148:Calmodulin-Binding Proteins; D047389:Casein Kinase I; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D011493:Protein Kinase C; D012694:Serine; D012967:Sodium Dodecyl Sulfate; D013049:Spectrin; D013755:Tetradecanoylphorbol Acetate; D000099291:Adducins; C028841:erythrocyte membrane band 4.1 protein