Extracellular HIV-1 Tat protein induces a rapid and selective activation of protein kinase C (PKC)-alpha, and -epsilon and -zeta isoforms in PC12 cells.
The addition in culture of extracellular HIV-1 Tat protein (0.1-1 nM) to PC12 cells induced a rapid increase of the bulk protein kinase C (PKC) catalytic activity. Among various PKC isoforms (alpha, beta I, beta II, delta, epsilon, eta, theta, and zeta) expressed in PC12 cells, Tat selectively stimulated alpha, epsilon, and zeta, as judged by activities in immunoprecipitates. Activation of these isoforms was suppressed by the tyrosine kinase inhibitor genistein. Moreover, PKC-zeta showed the fastest kinetics of activation in response to Tat, but PKC-alpha and PKC-epsilon showed the highest levels of activation. PKC-alpha activation was accompanied by a rise of intracellular IP3, while the PI 3-kinase inhibitors wortmannin and LY294002 suppressed PKC-epsilon activation. Taken together, these findings demonstrate that extracellular Tat shows a cytokine-like activity in PC12 cells, being able to trigger an intracellular signalling cascade which involves PKC-alpha, -epsilon, and -zeta.
Borgatti
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P
Division of Signal Transduction, Harvard Institute of Medicine, Beth Israel Hospital, Boston, Massachusettes 02115, USA.
Zauli
G
G
Cantley
L C
LC
Capitani
S
S
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015696:Gene Products, tat / Q000378:metabolism* / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D015497:HIV-1 / Q000737:chemistry*; D015544:Inositol 1,4,5-Trisphosphate / Q000032:analysis / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D016716:PC12 Cells; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors; D014764:Viral Proteins / Q000494:pharmacology; D000077191:Wortmannin; D054322:tat Gene Products, Human Immunodeficiency Virus
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D015696:Gene Products, tat; D007527:Isoenzymes; D009025:Morpholines; D014764:Viral Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D015544:Inositol 1,4,5-Trisphosphate; D019833:Genistein; D011493:Protein Kinase C; D000077191:Wortmannin