Tyrosine phosphorylation of biliary glycoprotein, a cell adhesion molecule related to carcinoembryonic antigen.
Biliary-glycoprotein (BGP), a cell adhesion molecule related to carcinoembryonic antigen (CEA), has been shown to exist as several alternatively spliced isoforms. Here we show that BGPa and BGPb are phosphorylated in the chronic myelogenous leukaemia cell line KG-1, which constitutively expresses several BGP isoforms, and Chinese hamster LR-73 cells transfected with the cDNAs encoding BGPa and BGPb. The phosphorylation can be augmented with the protein tyrosine phosphatase inhibitor ammonium vanadate and with TPA (an activator of protein kinase C). Phospho-amino acid analysis of phosphorylated BGPs demonstrated that phosphorylation occurs on serine, threonine and tyrosine residues. Phosphorylation reactions carried out in in vitro membrane preparations from KG-1 cells revealed a close association of BGP proteins with membrane associated protein tyrosine kinases. These observations suggest an association of BGP proteins with signal transduction molecules which is regulated by alternative splicing of the cytoplasmic domain.
Department of Biochemistry, University of Ottawa, Ontario, Canada.
D E
DE
Afar
C P
CP
Stanners
J C
JC
Bell
D000595:Amino Acid Sequence; D015703:Antigens, CD; D002272:Carcinoembryonic Antigen / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010750:Phosphoproteins / Q000378:metabolism; D019000:Phosphotyrosine; D016415:Sequence Alignment; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D015703:Antigens, CD; C069847:CD66 antigens; D002272:Carcinoembryonic Antigen; D015815:Cell Adhesion Molecules; D006023:Glycoproteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D019000:Phosphotyrosine; D014443:Tyrosine