Nakhost A, Forscher P, Sossin W S
Department of Neurology and Neurosurgery, McGill University, Montreal Neurological Institute, Quebec, Canada.
J Neurochem. 1998 Sep;71(3):1221-31. doi: 10.1046/j.1471-4159.1998.71031221.x.
Recently, two of the 10 vertebrate protein kinase C (PKC) isoforms, PKC betaII and PKC epsilon, have been shown to bind specifically to actin filaments, suggesting that these kinases may regulate cytoskeletal dynamics. Here, we present evidence that two PKCs from the marine mollusk Aplysia californica, PKC Apl I, a Ca2+-activated PKC, and PKC Apl II, a Ca2+-independent PKC most similar to PKC epsilon and eta, also bind F-actin. First, they both cosedimented with purified actin filaments in a phorbol ester-dependent manner. Second, they both translocated to the Triton-insoluble fraction of the nervous system after phorbol ester treatment. PKC Apl II could also partially translocate to actin filaments and associate with the Triton-insoluble fraction in the absence of phorbol esters. Translocation to purified actin filaments was increased in the presence of a PKC inhibitor, suggesting that PKC phosphorylation reduces PKC bound to actin. Although both kinases bound F-actin, actin was not sufficient to activate the kinases. In support of a physiological role for actin-PKC interactions, immunochemical localization of PKC Apl II in neuronal growth cones revealed a striking colocalization with F-actin. Our results are consistent with a role for actin-PKC interactions in regulating cytoskeletal dynamics in Aplysia.
最近，已证实10种脊椎动物蛋白激酶C（PKC）亚型中的两种，即PKCβII和PKCε，能特异性结合肌动蛋白丝，这表明这些激酶可能调节细胞骨架动力学。在此，我们提供证据表明，来自海生软体动物加州海兔的两种PKC，即Ca2+激活的PKC Apl I和与PKCε及η最为相似的Ca2+非依赖性PKC Apl II，也能结合F-肌动蛋白。首先，它们都以佛波酯依赖性方式与纯化的肌动蛋白丝共沉降。其次，在佛波酯处理后，它们都转位至神经系统的Triton不溶性组分中。在没有佛波酯的情况下，PKC Apl II也能部分转位至肌动蛋白丝并与Triton不溶性组分结合。在PKC抑制剂存在的情况下，转位至纯化肌动蛋白丝的情况增加，这表明PKC磷酸化会减少与肌动蛋白结合的PKC。尽管两种激酶都能结合F-肌动蛋白，但肌动蛋白不足以激活这些激酶。为支持肌动蛋白-PKC相互作用的生理作用，PKC Apl II在神经元生长锥中的免疫化学定位显示与F-肌动蛋白有显著的共定位。我们的结果与肌动蛋白-PKC相互作用在调节加州海兔细胞骨架动力学中的作用一致。
