Chang S, Hemmings H C, Aderem A
Laboratory of Signal Transduction, Rockefeller University, New York, New York 10021-6399, USA.
J Biol Chem. 1996 Jan 12;271(2):1174-8. doi: 10.1074/jbc.271.2.1174.
MacMARCKS (also known as myristoylated alanine-rich C kinase substrate (MARCKS)-related protein) is a member of the MARCKS family of protein kinase C substrates, which binds Ca2+/calmodulin in a phosphorylation-dependent manner. Immunoprecipitation demonstrated that MacMARCKS is present in both PC12 cells and in neurons. Upon depolarization of PC12 cells with 60 mM KCl, MacMARCKS phosphorylation increased 4-fold over basal levels in a Ca(2+)-dependent manner. By immunofluorescence microscopy, MacMARCKS was colocalized in PC12 cells to neurite tips with the synaptic vesicle membrane protein synaptophysin and to vesicles in the perinuclear region. Subcellular fractionation demonstrated that MacMARCKS associates tightly with membranes in PC12 cells. In Percoll-purified rat cerebrocortical synaptosomes, depolarization with 60 mM KCl in the presence of exogenous Ca2+ transiently increased MacMARCKS phosphorylation, whereas phorbol ester promoted a sustained increase in MacMARCKS phosphorylation. Subcellular fractionation of rat brain indicated that MacMARCKS was present in both soluble and particulate fractions; particulate MacMARCKS was associated with both small vesicles and highly purified synaptic vesicles. These results are consistent with a role for MacMARCKS in integrating Ca(2+)-calmodulin and protein kinase C-dependent signals in the regulation of neurosecretion.
MacMARCKS（也称为肉豆蔻酰化富含丙氨酸的C激酶底物（MARCKS）相关蛋白）是蛋白激酶C底物的MARCKS家族成员，它以磷酸化依赖的方式结合Ca2+/钙调蛋白。免疫沉淀表明MacMARCKS存在于PC12细胞和神经元中。用60 mM KCl使PC12细胞去极化后，MacMARCKS的磷酸化以Ca(2+)依赖的方式比基础水平增加了4倍。通过免疫荧光显微镜观察，MacMARCKS在PC12细胞中与神经突尖端的突触小泡膜蛋白突触素共定位，并与核周区域的小泡共定位。亚细胞分级分离表明MacMARCKS在PC12细胞中与膜紧密结合。在经Percoll纯化的大鼠大脑皮质突触体中，在外源Ca2+存在下用60 mM KCl去极化会短暂增加MacMARCKS的磷酸化，而佛波酯则促进MacMARCKS磷酸化的持续增加。大鼠脑的亚细胞分级分离表明MacMARCKS存在于可溶性和颗粒性部分中；颗粒性MacMARCKS与小泡和高度纯化的突触小泡都有关联。这些结果与MacMARCKS在整合Ca(2+)-钙调蛋白和蛋白激酶C依赖性信号以调节神经分泌中的作用一致。
