Borgatti P, Zauli G, Cantley L C, Capitani S
Division of Signal Transduction, Harvard Institute of Medicine, Beth Israel Hospital, Boston, Massachusettes 02115, USA.
Biochem Biophys Res Commun. 1998 Jan 14;242(2):332-7. doi: 10.1006/bbrc.1997.7877.
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.
在PC12细胞培养物中添加细胞外HIV-1 Tat蛋白（0.1 - 1 nM）会导致总体蛋白激酶C（PKC）催化活性迅速增加。根据免疫沉淀中的活性判断，在PC12细胞中表达的各种PKC同工型（α、βI、βII、δ、ε、η、θ和ζ）中，Tat选择性地刺激α、ε和ζ。这些同工型的激活被酪氨酸激酶抑制剂金雀异黄素抑制。此外，PKC-ζ对Tat的反应显示出最快的激活动力学，但PKC-α和PKC-ε显示出最高的激活水平。PKC-α的激活伴随着细胞内IP3的升高，而PI 3-激酶抑制剂渥曼青霉素和LY294002抑制PKC-ε的激活。综上所述，这些发现表明细胞外Tat在PC12细胞中表现出细胞因子样活性，能够触发涉及PKC-α、-ε和-ζ的细胞内信号级联反应。
