The cell adhesion molecule CD31 is phosphorylated after cell activation. Down-regulation of CD31 in activated T lymphocytes.
We report the independent cloning of the cDNA for CD31, a recently described cell adhesion molecule of the immunoglobulin gene superfamily present on platelets, granulocytes, monocytes, lymphocytes, and endothelial cells. Northern analysis revealed three major mRNA transcripts in Jurkat (a human T cell line) and K562 and HEL (leukemia cell lines) cells with an additional 5.3-kilobase transcript seen in cultured human umbilical vein endothelial cells. Following T cell activation, CD31 mRNA was down-regulated by Northern analysis, and decreased CD31 protein expression was confirmed by immunoblots. The down-regulation of CD31 was partially mediated by decreased transcription as demonstrated by nuclear run-on studies. CD31 became rapidly phosphorylated in platelets, Jurkat cells, and endothelial cells after cell activation. We were unable to demonstrate the presence of a phosphotyrosine in CD31 using monoclonal and polyclonal phosphotyrosine antibodies. In addition, CD31 phosphorylation in platelets was induced by phorbol ester and was blocked by staurosporin, a protein kinase C inhibitor, suggesting that CD31 phosphorylation is mediated by protein kinase C and involves serine and/or threonine residues. The phosphorylation of CD31 following cell activation may modulate its cellular adhesiveness, and the down-regulation of its expression may serve to impart target specificity and to localize effector lymphocytes to areas of inflammation.
Zehnder
J L
JL
Division of Hematology, Stanford University School of Medicine, California 94305-5112.
Hirai
K
K
Shatsky
M
M
McGregor
J L
JL
Levitt
L J
LJ
Leung
L L
LL
D000911:Antibodies, Monoclonal; D015214:Antigens, Differentiation, Myelomonocytic / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001792:Blood Platelets / Q000276:immunology; D015152:Blotting, Northern; D015139:Blotting, Southern; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D015723:Gene Library; D006801:Humans; D015151:Immunoblotting; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010766:Phosphorylation; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D015183:Restriction Mapping; D013601:T-Lymphocytes / Q000276:immunology*
D000911:Antibodies, Monoclonal; D015214:Antigens, Differentiation, Myelomonocytic; D015815:Cell Adhesion Molecules; D009838:Oligodeoxyribonucleotides; D019408:Platelet Endothelial Cell Adhesion Molecule-1