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Regulation of multiple functions of SHPS-1, a transmembrane glycoprotein, by its cytoplasmic region

2003; Elsevier BV; Volume: 309; Issue: 3 Linguagem: Inglês

10.1016/j.bbrc.2003.08.031

1090-2104

Ryuji Sato, Hiroshi Ohnishi, Hisae Kobayashi, Daisuke Kiuchi, Akiko Hayashi, Yuka Kaneko, Nakayuki Honma, Hideki Okazawa, Yukio Hirata, Takashi Matozaki,

Complement system in diseases

SHPS-1 is a receptor-type transmembrane glycoprotein, which contains four tyrosine residues in its cytoplasmic region, and the phosphorylation of these tyrosine residues serves the binding sites for SHP-2 protein–tyrosine phosphatase. Its extracellular region interacts with another membrane protein, CD47, thereby constituting a cell–cell communication system. We analyzed this ligand–receptor interaction using Chinese hamster ovary (CHO) cells expressing wild-type (WT) or mutant SHPS-1. The binding affinity of an SHPS-1 mutant such as ΔCyto, that lacked most of cytoplasmic region, or 4F, in which all four tyrosine residues in cytoplasmic region were substituted with phenylalanine, for a recombinant CD47-Fc was greater than that of WT. In addition, oligomerization of ΔCyto or 4F mutant by binding of CD47-Fc was greater than WT. Chemical cross-linking of SHPS-1 indicated that SHPS-1 formed a cis-dimer. Furthermore, WT cells exhibited a less polarized cell shape with decreased formation of actin stress fibers, compared with parental CHO cells and mutant SHPS-1 expressing cells. Prominent lamellipodium formation and membrane ruffling were also observed at leading edges of migrating WT cells but not at those of other mutant SHPS-1 expressing cells. These results suggest that the binding affinity of SHPS-1 to CD47, clustering ability of SHPS-1, and cytoskeletal reorganization are regulated by the cytoplasmic region of SHPS-1.