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

• Published in: Biochemical and biophysical research communications 2003-09, Vol.309 (3), p.584-590
• Main Authors: Sato, Ryuji, Ohnishi, Hiroshi, Kobayashi, Hisae, Kiuchi, Daisuke, Hayashi, Akiko, Kaneko, Yuka, Honma, Nakayuki, Okazawa, Hideki, Hirata, Yukio, Matozaki, Takashi
• Format: Article
• Language: English
• Subjects: Animals; Antigens, CD - metabolism; Antigens, Differentiation; Carrier Proteins - metabolism; CD47; CD47 Antigen; Cell Size; CHO Cells; Cricetinae; Cytoskeletal reorganization; Cytoskeleton - ultrastructure; Genes, ras; Ligands; Membrane Glycoproteins - chemistry; Membrane Glycoproteins - genetics; Membrane Glycoproteins - metabolism; Mutation; Neural Cell Adhesion Molecule L1 - chemistry; Neural Cell Adhesion Molecule L1 - genetics; Neural Cell Adhesion Molecule L1 - metabolism; Protein Structure, Tertiary; Receptor binding; Receptors, Immunologic; SHP-2; SHPS-1
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2003.08.031

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.