Geiges D, Marks F, Gschwendt M
German Cancer Research Center, Heidelberg.
Exp Cell Res. 1995 Jul;219(1):299-303. doi: 10.1006/excr.1995.1231.
The spontaneously immortalized human skin keratinocytes HaCaT contain protein kinase C (PKC) alpha, -delta, -epsilon, and -zeta. All PKC isoenzymes except PKC zeta are down-regulated by TPA as well as by bryostatin. However, with PKC delta, bryostatin but not TPA was found to be much less effective at high concentrations than at low ones. PKC delta expression at the protein and mRNA level is significantly suppressed in HaCaT cells I-7 and II-4, which are transfected with mutated c-Ha-ras. The expression of the other isoenzymes remains essentially unchanged in the ras-transfected cells compared to normal ones. PKC delta is lost when growing HaCaT cells in a medium obtained from the cultivation of ras-transfected cells ("ras-conditioned" medium). The factor secreted into the medium by the ras-transfected cells that is responsible for this effect appears to be TGF alpha, since the action of ras-conditioned medium on PKC delta expression can be overcome by the addition of an anti-TGF alpha antibody. Moreover, treatment of HaCaT cells with TGF alpha suppresses selectively the expression of the PKC isoenzyme delta.
自发永生化的人皮肤角质形成细胞HaCaT含有蛋白激酶C（PKC）α、δ、ε和ζ。除PKCζ外，所有PKC同工酶都可被佛波酯（TPA）以及苔藓抑素下调。然而，对于PKCδ，发现苔藓抑素在高浓度时的效果远不如低浓度时，而TPA则不然。在转染了突变型c-Ha-ras的HaCaT细胞I-7和II-4中，PKCδ在蛋白质和mRNA水平的表达均被显著抑制。与正常细胞相比，其他同工酶在转染了ras的细胞中的表达基本保持不变。当在从转染了ras的细胞培养物中获得的培养基（“ras条件培养基”）中培养HaCaT细胞时，PKCδ会消失。转染了ras的细胞分泌到培养基中导致这种效应的因子似乎是转化生长因子α（TGFα），因为添加抗TGFα抗体可以克服ras条件培养基对PKCδ表达的作用。此外，用TGFα处理HaCaT细胞会选择性地抑制PKC同工酶δ的表达。
