CD43 is associated with tyrosine kinase activity in human neutrophils

Abstract

CD43 appears to be involved in signal transduction, however, the mechanism of this function is unknown. Protein kinase activity was detected in neutrophils associated with CD43. Most of the protein kinase activity associated with these antigens was tyrosine kinase activity. The src family kinases lyn and hck were found to account for much of the associated tyrosine kinase activity. The data suggest that associated tyrosine kinase activity may play a role in signal transduction via CD43 to regulate other cell functions. J. Leukoc. Biol. 64: 800-802; 1998. Key Words: granulocyte · inflammation · signal transduction · protein kinase · membrane proteinCD43, also known as sialophorin, leukosialin, and leukocyte sialoglycoprotein, is a single-chain transmembrane protein that appears to play a role in cell adhesion [1][2][3] but can also transmit signals, such as the activation of T cells [4,5], neutrophils [6], and monocytes [7], and the induction of apoptosis in some hematopoietic progenitors [8]. After cell activation, CD43 is rapidly lost from the cell surface of neutrophils and lymphocytes by proteolysis [1]. CD43 is constitutively phosphorylated on serine on its intracellular domain, and the level of phosphorylation increases on cell activation. However, the mechanism by which CD43 participates in signal transduction is unclear [1].Protein phosphorylation is an important mechanism of regulating protein function. When CD43 was immunoprecipitated from solubilized neutrophils, protein tyrosine kinase activity associated with CD43 was detected in the immunoprecipitates. The src family kinases lyn and hck were found to account for much of this activity. The data suggest that tyrosine kinase activity associated with CD43 may play a role in the transduction of regulatory signals in neutrophils.Neutrophils were prepared from heparinized (2 units/mL) human venous blood as described [9], and were suspended at the indicated concentrations in 145 mM NaCl, 20 mM HEPES (GIBCO, Grand Island, NY), pH 7.3 (NaCl-HEPES).mAb AHN-12 (IgG1; CD45) has been previously described [10]. CD43 mAbs were obtained from the Fifth International Workshop and Conference on Human Leukocyte Differentiation Antigens, including the following CD43 mAbs: MEM-59, G10.2, L60, 10G7, BRA7G, and 6E5. The T cell-reactive mAbs 5T-011 (MEM-24; IgG1) and 5T-012 (263K 3F4; IgG2a) were obtained from the T cell panel of the same workshop. AHN-17 (IgG1) and AHN-17.1 (IgG1) recognize migration inhibitoryrelated protein-8 and -14, and were described in the same workshop. Polyclonal antibodies to yes, src, lck, lyn, fyn, hck, and fgr were obtained from Santa Cruz Biotechnology, Santa Cruz, CA. Polyclonal antibodies to yes, fyn, src, and fgr were also obtained as a gift from Dr. F. Uckun, University of Minnesota Medical School, Minneapolis, MN. Antiserum to syk was purchased from Upstate Biotechnology, Inc. (Lake Placid, NY). Normal mouse serum (NMS) and normal rat serum (NRS) were purchased from Sigma Chemical Co. (St. Louis, MO).Immunoprecipitation was perfo...

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Functional Mapping of the Cytoplasmic Region of Intercellular Adhesion Molecule-3 Reveals Important Roles for Serine Residues

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