title: CD157 undergoes ligand-independent dimerization and colocalizes with caveolin in CHO and MCA102 fibroblasts.
abstract: CD157, a glycosylphosphatidylinositol (GPI)-anchored glycoprotein, has recently been shown to induce protein tyrosine phosphorylation in monocytes differentiated from HL-60 cells (mHL-60) in a ligand-dependent manner, but in a ligand-independent manner in stable CD157-transfected CHO (CHO/CD157) and MCA102 (MCA/CD157) fibroblasts [Cell Signal. 11 (1999) 891-897.]. Many GPI-anchored proteins need to be clustered by their ligands or antibodies to induce redistribution to caveolae and a concomitant activation of the associated signal-transducing proteins [Nature 387 (1997) 569-572.]. Here, we demonstrate that CD157, independent of antibody crosslinking, undergoes dimerization with disulfide bond formation and localization in caveolae in CHO/CD157 and MCA/CD157 fibroblasts. However, the native CD157 induced in mHL-60 cells remains a monomer form. The structural integrity of caveolae is required for the association of CD157 with caveolin and CD157-mediated tyrosine kinase signalling in the fibroblasts. We propose that an overexpression of CD157 could lead to its dimerization and relocation to caveolae and to further result in the initiation of signalling processes.
authors.affiliation: Department of Biochemistry, National University of Singapore, Singapore.
authors.forename: Fubo
authors.initials: F
authors.lastname: Liang
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Qi
authors.forename: Chan Fong
authors.initials: CF
authors.lastname: Chang
mesh_terms: D036541:ADP-ribosyl Cyclase / Q000378:metabolism*; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D016466:CHO Cells; D021941:Caveolae / Q000378:metabolism; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism*; D002451:Cell Compartmentation / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D019281:Dimerization; D005057:Eukaryotic Cells / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D058851:GPI-Linked Proteins; D018922:HL-60 Cells; D006801:Humans; D008024:Ligands; D015394:Molecular Structure; D017434:Protein Structure, Tertiary / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D015703:Antigens, CD; C495540:CAV1 protein, human; D051242:Caveolin 1; D022461:Caveolins; D058851:GPI-Linked Proteins; D008024:Ligands; D036541:ADP-ribosyl Cyclase; C087521:ADP-ribosyl cyclase 2