Dehvari Nodi, Cedazo-Minguez Angel, Isacsson Ola, Nilsson Tatjana, Winblad Bengt, Karlström Helena, Benedikz Eirikur, Cowburn Richard F
Karolinska Institutet, NVS, KI-Alzheimer Disease Research Center, Novum, Stockholm, Sweden.
J Neurochem. 2007 Aug;102(3):848-57. doi: 10.1111/j.1471-4159.2007.04571.x. Epub 2007 Apr 16.
Presenilins (PSs) are involved in processing several proteins such as the amyloid precursor protein (APP), as well as in pathways for cell death and survival. We previously showed that some familial Alzheimer's disease PS mutations cause increased basal and acetylcholine muscarinic receptor-stimulated phospholipase C (PLC) activity which was gamma-secretase dependent. To further evaluate the dependence of PLC on PSs we measured PLC activity and the activation of variant protein kinase C (PKC) isoforms in mouse embryonic fibroblasts (MEFs) lacking either PS1, PS2, or both. PLC activity and PKCalpha and PKCgamma activations were significantly lower in PS1 and PS2 double knockout MEFs after PLC stimulation. Protein levels of PKCalpha and PKCgamma were lower in PS1 and PS2 double knockout MEFs. In contrast, PKCdelta levels were significantly elevated in PS1 and PS2 double knockout as well as in PS1 knockout MEFs. Also, PKCdelta levels were lowered after transfection of PS1 into PS1 knockout or PS double knockout MEFs. Using APP knockout MEFs we showed that the expression of PKCalpha, but not the other PKC isoforms is partially dependent on APP and can be regulated by APP intracellular domain (AICD). These results show that PLC and PKC activations are modulated by PS and also that PSs differentially regulate the expression of PKC isoforms by both APP/AICD-dependent and independent mechanisms.
早老素（PSs）参与多种蛋白质的加工过程，如淀粉样前体蛋白（APP），同时也参与细胞死亡和存活途径。我们之前发现，一些家族性阿尔茨海默病的PS突变会导致基础和乙酰胆碱毒蕈碱受体刺激的磷脂酶C（PLC）活性增加，且这种增加依赖于γ-分泌酶。为了进一步评估PLC对PSs的依赖性，我们在缺乏PS1、PS2或两者的小鼠胚胎成纤维细胞（MEFs）中测量了PLC活性以及变体蛋白激酶C（PKC）亚型的激活情况。在PLC刺激后，PS1和PS2双敲除MEFs中的PLC活性以及PKCα和PKCγ的激活显著降低。PS1和PS2双敲除MEFs中PKCα和PKCγ的蛋白水平较低。相反，在PS1和PS2双敲除以及PS1敲除的MEFs中，PKCδ水平显著升高。此外，将PS1转染到PS1敲除或PS双敲除MEFs后，PKCδ水平降低。利用APP敲除MEFs，我们发现PKCα的表达部分依赖于APP，而其他PKC亚型则不然，并且PKCα的表达可由APP细胞内结构域（AICD）调节。这些结果表明，PLC和PKC的激活受PS调节，并且PSs通过APP/AICD依赖和独立机制对PKC亚型的表达进行差异调节。
