Arendt C W, Hsi G, Ostergaard H L
Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Canada.
J Immunol. 1995 Dec 1;155(11):5095-103.
CD45 is a transmembrane protein tyrosine phosphatase required for signal transduction through the Ag receptor complexes of T and B lymphocytes. Herein, we demonstrate that immobilized mAbs to the external domain of CD45 induce rapid and dramatic morphologic changes in a variety of T cell lines, including CD8+ cytotoxic clones. CD45-induced morphologic changes can be inhibited by the cytoskeletal inhibitors cytochalasin D and E and by the protein tyrosine kinase inhibitor herbimycin A. Consistent with the requirement for tyrosine kinase activity, tyrosine phosphorylation of proteins at about 60 to 75 kDa and 115 to 130 kDa is increased upon engagement with immobilized anti-CD45 mAb with kinetics paralleling the observed changes in morphology. The phosphorylation of these proteins is inhibited by tyrosine kinase inhibitors at concentrations that also inhibit changes in morphology. The phosphoproteins induced when cells are added to immobilized anti-CD45 are co-immunoprecipitated with p56lck, suggesting that this tyrosine kinase might play a role in the phosphorylation of these proteins. Consistent with this, there is no increase in the phosphorylation of these proteins in p56lck-deficient CTLL-2 cells in response to immobilized anti-CD45 mAb. An important role for p56lck in the morphologic pathway is further supported by the observation that p56lck-deficient human J.CAM1.6 cells, in contrast to the parental Jurkat line, cannot be induced to undergo morphologic changes. Taken together, these results suggest a possible role for CD45 in coordinating a cytoskeletal remodeling cascade that may be important in cell activation.
CD45是一种跨膜蛋白酪氨酸磷酸酶，是T和B淋巴细胞通过抗原受体复合物进行信号转导所必需的。在此，我们证明，针对CD45胞外域的固定化单克隆抗体可在多种T细胞系中诱导快速且显著的形态变化，包括CD8 + 细胞毒性克隆。CD45诱导的形态变化可被细胞骨架抑制剂细胞松弛素D和E以及蛋白酪氨酸激酶抑制剂赫曲霉素A抑制。与酪氨酸激酶活性的需求一致，在与固定化抗CD45单克隆抗体结合后，约60至75 kDa和115至130 kDa的蛋白质酪氨酸磷酸化增加，其动力学与观察到的形态变化平行。这些蛋白质的磷酸化在也抑制形态变化的浓度下被酪氨酸激酶抑制剂抑制。当细胞与固定化抗CD45抗体结合时诱导产生的磷酸化蛋白与p56lck共同免疫沉淀，表明这种酪氨酸激酶可能在这些蛋白质的磷酸化中起作用。与此一致，在p56lck缺陷的CTLL - 2细胞中，针对固定化抗CD45单克隆抗体的反应中，这些蛋白质的磷酸化没有增加。p56lck缺陷的人J.CAM1.6细胞与亲本Jurkat细胞系不同，不能被诱导发生形态变化，这一观察结果进一步支持了p56lck在形态学途径中的重要作用。综上所述，这些结果表明CD45在协调可能对细胞激活很重要的细胞骨架重塑级联反应中可能发挥作用。
