Asada Akiko, Yamamoto Naoyuki, Gohda Masaki, Saito Taro, Hayashi Nobuhiro, Hisanaga Shin-Ichi
Department of Biological Sciences, Tokyo Metropolitan University, Hachiohji, Tokyo, Japan.
J Neurochem. 2008 Aug;106(3):1325-36. doi: 10.1111/j.1471-4159.2008.05500.x. Epub 2008 May 26.
Cdk5 is a member of the cyclin-dependent kinases (Cdks), activated by the neuron-specific activator p39 or p35. The activators also determine the cytoplasmic distribution of active Cdk5, but the mechanism is not yet known. In particular, little is known for p39. p39 and p35 contain localization motifs, such as a second Gly for myristoylation and Lys clusters in the N-terminal p10 region. Using mutant constructs, we investigated the cellular distribution mechanism. We observed that p39 localizes the active Cdk5 complex in the perinuclear region and at the plasma membrane as does p35. We demonstrated the myristoylation of both p39 and p35, and found that it is a major determinant of their membrane association. Plasma membrane targeting depends on the amino acid sequence containing the Lys-cluster in the N-terminal p10 region. In contrast, a non-myristoylated Ala mutant (p39G2A or p35G2A) showed nuclear localization with stronger accumulation of p39G2A than p35G2A. These results indicate that myristoylation regulates the membrane association of p39 as well as p35 and that the Lys cluster controls their trafficking to the plasma membrane. The differential nuclear accumulation of p39 and p35 suggests their segregated functions, p35-Cdk5 in the cytoplasm and p39-Cdk5 in the nucleus.
细胞周期蛋白依赖性激酶5（Cdk5）是细胞周期蛋白依赖性激酶（Cdks）家族的成员，由神经元特异性激活剂p39或p35激活。这些激活剂还决定了活性Cdk5在细胞质中的分布，但其机制尚不清楚。特别是，对于p39了解甚少。p39和p35含有定位基序，如用于肉豆蔻酰化的第二个甘氨酸和N端p10区域的赖氨酸簇。我们使用突变体构建体研究了细胞分布机制。我们观察到，p39与p35一样，将活性Cdk5复合物定位在核周区域和质膜上。我们证实了p39和p35均发生了肉豆蔻酰化，并发现这是它们与膜结合的主要决定因素。质膜靶向取决于N端p10区域中包含赖氨酸簇的氨基酸序列。相比之下，非肉豆蔻酰化的丙氨酸突变体（p39G2A或p35G2A）表现出核定位，且p39G2A的积累比p35G2A更强。这些结果表明，肉豆蔻酰化调节p39以及p35与膜的结合，赖氨酸簇控制它们向质膜的转运。p39和p35在核内的不同积累表明它们具有不同的功能，即细胞质中的p35-Cdk5和细胞核中的p39-Cdk5。
