Park Bum-Chan, Yim Yang-In, Zhao Xiaohong, Olszewski Maciej B, Eisenberg Evan, Greene Lois E
Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
J Cell Sci. 2015 Oct 15;128(20):3811-21. doi: 10.1242/jcs.171058. Epub 2015 Sep 7.
Cyclin-G-associated kinase (GAK), the ubiquitously expressed J-domain protein, is essential for the chaperoning and uncoating of clathrin that is mediated by Hsc70 (also known as HSPA8). Adjacent to the C-terminal J-domain that binds to Hsc70, GAK has a clathrin-binding domain that is linked to an N-terminal kinase domain through a PTEN-like domain. Knocking out GAK in fibroblasts caused inhibition of clathrin-dependent trafficking, which was rescued by expressing a 62-kDa fragment of GAK, comprising just the clathrin-binding and J-domains. Expressing this fragment as a transgene in mice rescued the lethality and the histological defects caused by knocking out GAK in the liver or in the brain. Furthermore, when both GAK and auxilin (also known as DNAJC6), the neuronal-specific homolog of GAK, were knocked out in the brain, mice expressing the 62-kDa GAK fragment were viable, lived a normal life-span and had no major behavior abnormalities. However, these mice were about half the size of wild-type mice. Therefore, the PTEN-like domains of GAK and auxilin are not essential for Hsc70-dependent chaperoning and uncoating of clathrin, but depending on the tissue, these domains appear to increase the efficiency of these co-chaperones.
细胞周期蛋白G相关激酶（GAK）是一种在全身广泛表达的J结构域蛋白，对于由Hsc70（也称为HSPA8）介导的网格蛋白的伴侣作用和解聚至关重要。在与Hsc70结合的C末端J结构域附近，GAK有一个网格蛋白结合结构域，该结构域通过一个类PTEN结构域与N末端激酶结构域相连。在成纤维细胞中敲除GAK会导致网格蛋白依赖性运输受到抑制，而表达仅包含网格蛋白结合结构域和J结构域的62 kDa的GAK片段可挽救这种抑制。在小鼠中作为转基因表达该片段可挽救因在肝脏或大脑中敲除GAK而导致的致死性和组织学缺陷。此外，当在大脑中同时敲除GAK和辅助蛋白（也称为DNAJC6，GAK的神经元特异性同源物）时，表达62 kDa GAK片段的小鼠能够存活，寿命正常，且没有明显的行为异常。然而，这些小鼠的体型约为野生型小鼠的一半。因此，GAK和辅助蛋白的类PTEN结构域对于Hsc70依赖性的网格蛋白伴侣作用和解聚不是必需的，但根据组织不同，这些结构域似乎会提高这些共伴侣蛋白的效率。
