Nakamura Jiro
Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba-shi, Ibaraki-ken, Japan.
Biochim Biophys Acta. 2008 May;1781(5):277-81. doi: 10.1016/j.bbalip.2008.03.007. Epub 2008 Apr 8.
We have shown previously that insulin attenuates beta1-adrenergic receptor (beta1-AR)-mediated lipolysis via activation of protein kinase C (PKC) in rat adipocytes. This antilipolysis persists after removal of insulin and is independent of the phosphodiesterase 3B activity, and phorbol 12-myristate 13-acetate (PMA) could substitute for insulin to produce the same effect. Here, we attempted to identify the PKC isoform responsible for antilipolysis. Isolated adipocytes were treated with high and low concentrations of PMA for up to 6 h to degrade specific PKC isoforms. In the PMA-treated cells, the downregulation profiles of PKC isoforms alpha and betaI, but not betaII, delta, epsilon, or zeta, correlated well with a decrease of lipolysis-attenuating effect of PMA. After rats fasted for 24 h, adipocyte expression of PKC isoform alpha increased, while expression of PKCdelta decreased. Fasting did not change the potency of PMA to attenuate lipolysis, however. The lipolysis-attenuating effect of PMA was blocked by the PKCbetaI/betaII inhibitor LY 333531, but not by the PKCbetaII inhibitor CGP 53353 or the PKCdelta inhibitor rottlerin. These data suggest that PKCbetaI interacts with beta1-AR signaling and attenuates lipolysis in rat adipocytes.
我们之前已经表明，胰岛素通过激活大鼠脂肪细胞中的蛋白激酶C（PKC）来减弱β1-肾上腺素能受体（β1-AR）介导的脂解作用。在去除胰岛素后，这种抗脂解作用仍然存在，并且独立于磷酸二酯酶3B的活性，佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）可以替代胰岛素产生相同的效果。在此，我们试图确定负责抗脂解作用的PKC同工型。分离的脂肪细胞用高浓度和低浓度的PMA处理长达6小时，以降解特定的PKC同工型。在PMA处理的细胞中，PKC同工型α和βI（而非βII、δ、ε或ζ）的下调情况与PMA脂解减弱作用的降低密切相关。大鼠禁食24小时后，PKC同工型α在脂肪细胞中的表达增加，而PKCδ的表达降低。然而，禁食并未改变PMA减弱脂解的效力。PMA的脂解减弱作用被PKCβI/βII抑制剂LY 333531阻断，但未被PKCβII抑制剂CGP 53353或PKCδ抑制剂rottlerin阻断。这些数据表明，PKCβI与β1-AR信号相互作用并减弱大鼠脂肪细胞中的脂解作用。
