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Investigative Ophthalmology & Visual Science, Vol 29, 1794-1799, Copyright © 1988 by Association for Research in Vision and Ophthalmology
ARTICLES AND REPORTS |
CA Heth and SY Schmidt
Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Boston, MA 02114.
Incubation of confluent cultures of rat retinal pigment epithelium (RPE) with 32P-orthophosphate resulted in the incorporation of 32P into proteins, RNA and the nucleoside phosphates ADP, GDP, ATP and GTP. RPE cultures incubated with phorbol-12-myristate-13-acetate (PMA), a known activator of protein kinase C, did not significantly change the incorporation of 32P into total protein, RNA or the nucleoside phosphates ADP, GDP, ATP and GTP. However, PMA exposure specifically increased phosphorylation of five proteins with molecular weights of 80 kilodaltons (K), 56K, 35K, 33K, and 29K having isoelectric points between 4.3 and 6.5. PMA treated cultures also showed dephosphorylation of two proteins having molecular weights of about 33K. The observed increase in 80K phosphorylation suggests that protein kinase C is present and activated by PMA in the RPE.
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