Adhesion or plasmin regulates tyrosine phosphorylation of a novel membrane glycoprotein p80/gp140/CUB domain-containing protein 1 in epithelia.
Suspension of cultured human foreskin keratinocytes (HKs) with trypsin phosphorylates tyrosine residues on an 80-kDa membrane glycoprotein, p80 (Xia, Y., Gil, S. G., and Carter, W. G. (1996) J. Cell Biol. 132, 727-740). Readhesion dephosphorylates p80. Sequencing of a p80 cDNA established identity to CUB domain-containing protein 1 (CDCP1), a gene elevated in carcinomas. CDCP1/p80 cDNA encodes three extracellular CUB domains, a transmembrane domain, and two putative cytoplasmic Tyr phosphorylation sites. Treatment of adherent HKs with suramin, a heparin analogue, or inhibitors of phosphotyrosine phosphatases (PTPs; vanadate or calpeptin) increases phosphorylation of p80 and a novel 140-kDa membrane glycoprotein, gp140. Phosphorylated gp140 was identified as a trypsin-sensitive precursor to p80. Identity was confirmed by digestion and phosphorylation studies with recombinant gp140-GFP. Plasmin, a serum protease, also converts gp140 to p80, providing biological significance to the cleavage in wounds. Phosphorylation of gp140 and p80 are mediated by Src family kinases at multiple Tyr residues including Tyr(734). Dephosphorylation is mediated by PTP(s). Conversion of gp140 to p80 prolongs phosphorylation of p80 in response to suramin and changes in adhesion. This distinguishes gp140 and p80 and explains the relative abundance of phosphorylated p80 in trypsinized HKs. We conclude that phosphorylation of gp140 is dynamic and balanced by Src family kinase and PTPs yielding low equilibrium phosphorylation. We suggest that the balance is altered by conversion of gp140 to p80 and by adhesion, providing a novel transmembrane phosphorylation signal in epithelial wounds.
Brown
Tod A
TA
Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA. wcarter@fhcrc.org
Yang
Tai Mei
TM
Zaitsevskaia
Tatiana
T
Xia
Yuping
Y
Dunn
Clarence A
CA
Sigle
Randy O
RO
Knudsen
Beatrice
B
Carter
William G
WG
D020816:Amino Acid Motifs; D015703:Antigens, CD; D000951:Antigens, Neoplasm; D015153:Blotting, Western; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000737:chemistry*; D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004848:Epithelium / Q000378:metabolism*; D005341:Fibrinolysin / Q000737:chemistry / Q000378:metabolism*; D015723:Gene Library; D006023:Glycoproteins / Q000737:chemistry*; D049452:Green Fluorescent Proteins; D006493:Heparin / Q000737:chemistry; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D013058:Mass Spectrometry; D008562:Membrane Glycoproteins / Q000737:chemistry*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry*; D009841:Oligonucleotides / Q000737:chemistry; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D019947:Receptors, Interleukin-6; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013498:Suramin / Q000737:chemistry / Q000494:pharmacology; D014357:Trypsin / Q000737:chemistry / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry*
D015703:Antigens, CD; D000951:Antigens, Neoplasm; C432044:CDCP1 protein, human; D015815:Cell Adhesion Molecules; D018076:DNA, Complementary; C033904:GP 140; D006023:Glycoproteins; C508603:IL6R protein, human; D008164:Luminescent Proteins; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D009841:Oligonucleotides; D019947:Receptors, Interleukin-6; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D014443:Tyrosine; D013498:Suramin; D006493:Heparin; D010744:Phosphoric Monoester Hydrolases; D014357:Trypsin; D005341:Fibrinolysin