Ohnishi Hiroshi, Kobayashi Hisae, Okazawa Hideki, Ohe Yoshihide, Tomizawa Kyoko, Sato Ryuji, Matozaki Takashi
Biosignal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-Machi, Maebashi, Gunma 371-8512, Japan.
J Biol Chem. 2004 Jul 2;279(27):27878-87. doi: 10.1074/jbc.M313085200. Epub 2004 Apr 28.
SHPS-1 is a transmembrane protein whose cytoplasmic region undergoes tyrosine phosphorylation and then binds the protein-tyrosine phosphatase SHP-2. Formation of the SHPS-1-SHP-2 complex is implicated in regulation of cell migration. In addition, SHPS-1 and its ligand CD47 constitute an intercellular recognition system that contributes to inhibition of cell migration by cell-cell contact. The ectodomain of SHPS-1 has now been shown to be shed from cells in a reaction likely mediated by a metalloproteinase. This process was promoted by activation of protein kinase C or of Ras, and the released ectodomain exhibited minimal CD47-binding activity. Metalloproteinases catalyzed the cleavage of a recombinant SHPS-1-Fc fusion protein in vitro, and the primary cleavage site was localized to the juxtamembrane region of SHPS-1. Forced expression of an SHPS-1 mutant resistant to ectodomain shedding impaired cell migration, cell spreading, and reorganization of the actin cytoskeleton. It also increased the tyrosine phosphorylation of paxillin and FAK triggered by cell adhesion. These results suggest that shedding of the ectodomain of SHPS-1 plays an important role in regulation of cell migration and spreading by this protein.
SHPS-1是一种跨膜蛋白，其胞质区域会发生酪氨酸磷酸化，然后与蛋白酪氨酸磷酸酶SHP-2结合。SHPS-1-SHP-2复合物的形成与细胞迁移的调控有关。此外，SHPS-1及其配体CD47构成了一个细胞间识别系统，该系统通过细胞间接触有助于抑制细胞迁移。现已表明，SHPS-1的胞外结构域会在可能由金属蛋白酶介导的反应中从细胞上脱落。这一过程通过蛋白激酶C或Ras的激活而得到促进，并且释放的胞外结构域表现出最小的CD47结合活性。金属蛋白酶在体外催化重组SHPS-1-Fc融合蛋白的裂解，并且主要裂解位点定位于SHPS-1的近膜区域。对胞外结构域脱落具有抗性的SHPS-1突变体体的强制表达会损害细胞迁移、细胞铺展以及肌动蛋白细胞骨架的重组。它还增加了由细胞黏附触发的桩蛋白和黏着斑激酶的酪氨酸磷酸化。这些结果表明，SHPS-1胞外结构域的脱落在此蛋白对细胞迁移和铺展的调控中起重要作用。
