Effect of tumour promoting agents on protein phosphorylation in human placenta.
1. The effects of okadaic acid (OA) and phorbol-12-myristate-13-acetate (PMA) on protein phosphorylation were studied in human term placentas. 2. When samples treated with tumour promoters were compared with untreated samples, the phosphorylation of a 135 kDa protein was significantly decreased; OA also produced a decrease in phosphorylation of a 24 kDa protein. 3. Both substances produced an alteration in the proportions of bands of masses 170, 65 and 24 kDa, relative to total phosphorylation; PMA treatment also affected the band of mass 135 kDa. 4. Placental cell extracts were also subjected to Western blotting with a protein kinase C (PKC) antibody, reportedly specific for the alpha- and beta-isoforms. 5. Two immunoreactive proteins were detected; an 80 kDa band, presumably corresponding to the alpha- or beta-PKC, and a 64 kDa protein, which could be a degradation production of the 80 kDa protein or it could correspond to another form of the enzyme. The expression of PKC did not change on treatment with PMA.
Bischof
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Department of Medical Biochemistry, University of the Witwatersrand Medical School, Parktown, Johannesburg, South Africa.
Hammond
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KD
D001345:Autoradiography; D015153:Blotting, Western; D002273:Carcinogens / Q000494:pharmacology*; D004988:Ethers, Cyclic / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008970:Molecular Weight; D019319:Okadaic Acid; D010766:Phosphorylation / Q000187:drug effects; D010920:Placenta / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014021:Tissue Preservation
D002273:Carcinogens; D004988:Ethers, Cyclic; D011257:Pregnancy Proteins; D019319:Okadaic Acid; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate