Novel phosphorylation at a mitotic site, serine 75, in human pp60c-src from unsynchronized human tumor cells having a spherical morphology.
Endogenous pp60c-src from Y79 unsynchronized human retinoblastoma cells is phosphorylated at an additional N-terminal serine residue relative to unsynchronized fibroblast pp60c-src. We confirmed that the novel phosphorylation site is Ser 75, which is the same as that phosphorylated in overexpressed human pp60c-src during NIH3T3 cell mitosis. We also showed that the Ser 75 phosphorylation pattern correlates with cell rounding in 14 various unsynchronized human tumor cell lines. Especially, pp60c-src from Lu135 having a spherical morphology similar to that of Y79 is phosphorylated as high as Y79 pp60c-src. Mitotic spherical cells of the epithelial-like HepG2 express pp60c-src phosphorylated on Ser 75. On the other hand, Y79 pp60c-src is phosphorylated on Ser 75 throughout the cell cycle. These data suggest that this phosphorylation may be important in spherical cell morphology.
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D005134:Eye Neoplasms; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D051379:Mice; D008938:Mitosis / Q000187:drug effects; D008969:Molecular Sequence Data; D015739:Nocodazole / Q000494:pharmacology; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012175:Retinoblastoma; D012694:Serine; D014162:Transfection; D014407:Tumor Cells, Cultured
D010446:Peptide Fragments; D010710:Phosphates; D011994:Recombinant Proteins; D012694:Serine; D016392:Proto-Oncogene Proteins pp60(c-src); D015739:Nocodazole