title: Hematopoietic protein-1 regulates the actin membrane skeleton and membrane stability in murine erythrocytes.
abstract: Hematopoietic protein-1 (Hem-1) is a hematopoietic cell specific member of the WAVE (Wiskott-Aldrich syndrome verprolin-homologous protein) complex, which regulates filamentous actin (F-actin) polymerization in many cell types including immune cells. However, the roles of Hem-1 and the WAVE complex in erythrocyte biology are not known. In this study, we utilized mice lacking Hem-1 expression due to a non-coding point mutation in the Hem1 gene to show that absence of Hem-1 results in microcytic, hypochromic anemia characterized by abnormally shaped erythrocytes with aberrant F-actin foci and decreased lifespan. We find that Hem-1 and members of the associated WAVE complex are normally expressed in wildtype erythrocyte progenitors and mature erythrocytes. Using mass spectrometry and global proteomics, Coomassie staining, and immunoblotting, we find that the absence of Hem-1 results in decreased representation of essential erythrocyte membrane skeletal proteins including α- and β- spectrin, dematin, p55, adducin, ankyrin, tropomodulin 1, band 3, and band 4.1. Hem1⁻/⁻ erythrocytes exhibit increased protein kinase C-dependent phosphorylation of adducin at Ser724, which targets adducin family members for dissociation from spectrin and actin, and subsequent proteolysis. Increased adducin Ser724 phosphorylation in Hem1⁻/⁻ erythrocytes correlates with decreased protein expression of the regulatory subunit of protein phosphatase 2A (PP2A), which is required for PP2A-dependent dephosphorylation of PKC targets. These results reveal a novel, critical role for Hem-1 in the homeostasis of structural proteins required for formation and stability of the actin membrane skeleton in erythrocytes.
authors: Department of Comparative Medicine, University of Washington, Seattle, Washington, United States of America.
authors: Maia M
authors: MM
authors: Chan
authors: Jason M
authors: JM
authors: Wooden
authors: Mark
authors: M
authors: Tsang
authors: Diana M
authors: DM
authors: Gilligan
authors: Dinesh K
authors: DK
authors: Hirenallur-S
authors: Greg L
authors: GL
authors: Finney
authors: Eric
authors: E
authors: Rynes
authors: Michael
authors: M
authors: Maccoss
authors: Julita A
authors: JA
authors: Ramirez
authors: Heon
authors: H
authors: Park
authors: Brian M
authors: BM
authors: Iritani
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D004910:Erythrocyte Membrane / Q000378:metabolism*; D017353:Gene Deletion; D051379:Mice; D010766:Phosphorylation; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism; D013997:Time Factors; D059467:Transcriptome; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C534032:Hem1 protein, mouse; C495774:Wasf1 protein, mouse; D051300:Wiskott-Aldrich Syndrome Protein Family