CD10/neutral endopeptidase 24.11 is phosphorylated by casein kinase II and coassociates with other phosphoproteins including the lyn src-related kinase.
CD10/neutral endopeptidase 24.11 (NEP) regulates peptidemediated proliferation of lymphoid progenitors and certain epithelial cells and is itself regulated by cellular proliferation. To further characterize mechanisms by which cell-surface signaling might regulate CD10/NEP expression, we determined whether CD10/NEP was phosphorylated and whether the enzyme co-associated with additional cellular phosphoproteins. The CD10/NEP cytoplasmic tall contains two consensus recognition sequences for casein kinase II (CKII), a serine and threonine kinase that increases in activity following peptide signaling. In standard in vitro kinase assays, CKII phosphorylated full-length recombinant CD10/NEP but did not phosphorylate a truncated CD10/NEP protein that lacked the transmembrane region and cytoplasmic tail. To determine whether CD10/NEP might interact with additional cellular phosphoproteins, in vitro kinase assays were performed on CD10/NEP immune complexes from Nalm-6 cells. Three additional tyrosine phosphoproteins of approximately 40 kD, approximately 58 kD, and approximately 75 kD were identified in the CD10/NEP immunoprecipitates. The approximately 56-kD CD10/NEP-associated phosphoprotein was immunoprecipitated with an anti-lyn antibody confirming its identity as the lyn src-related kinase. Taken together, these data indicate that CD10/NEP is itself phosphorylated by CKII and that CD10/NEP co-associates with additional tyrosine phosphoproteins including lyn.
Ganju
R K
RK
Department of Medicine, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
Shpektor
R G
RG
Brenner
D G
DG
Shipp
M A
MA
D000818:Animals; D016466:CHO Cells / Q000378:metabolism; D047390:Casein Kinase II; D006224:Cricetinae; D003412:Cricetulus; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D046911:Macromolecular Substances; D009363:Neoplasm Proteins / Q000378:metabolism; D015260:Neprilysin / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000473:pathology; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured; D019061:src-Family Kinases / Q000378:metabolism*
D018076:DNA, Complementary; D046911:Macromolecular Substances; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D015260:Neprilysin