A Coated Vesicle-associated Kinase of 104 kDa (CVAK104) Induces Lysosomal Degradation of Frizzled 5 (Fzd5)*
A Coated Vesicle-associated Kinase of 104 kDa (CVAK104) Induces Lysosomal Degradation of Frizzled 5 (Fzd5)*
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DOI：
10.1074/jbc.m109.039313
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发表时间：
2009-07
期刊：
影响因子：
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通讯作者：
T. Terabayashi;Y. Funato;M. Fukuda;H. Miki
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文献类型：
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作者：
T. Terabayashi;Y. Funato;M. Fukuda;H. Miki
受体内化被认为是控制许多细胞表面受体的重要机制。该事件不仅有助于调节信号转导，而且还调节细胞表面受体的量。Frizzleds（Fzds）是Wnt配体的七次跨膜受体家族蛋白。最近的研究表明，Fzd 5在响应Wnt刺激时被内化以激活下游信号通路。内化后，Fzd 5似乎再循环回到质膜。然而，内化的Fzd 5是否被分选到溶酶体中进行蛋白质降解仍不清楚。我们在这里报告，包被囊泡相关激酶104 kDa（CVAK 104）选择性诱导Fzd 5的溶酶体降解。我们确定CVAK 104作为一种新的结合伙伴的Dishevelled（Dvl），支架蛋白在Wnt信号通路。有趣的是，我们发现CVAK 104也与Fzd 5相互作用，但不与Fzd 1或Fzd 4相互作用。CVAK 104通过网格蛋白介导的途径选择性地诱导Fzd 5的细胞内积累，该途径被Rab 5的显性负性形式的共表达抑制。Fzd 5随后通过溶酶体途径降解。事实上，通过RNA干扰敲低内源性CVAK 104导致Fzd 5的量增加。相反，Wnt处理诱导Fzd 5内化，但不刺激其降解。CVAK 104的过表达或敲低分别导致Wnt/β-连环蛋白途径的显著抑制或激活。这些结果表明，CVAK 104通过诱导溶酶体降解来调节Fzd 5的量，这可能有助于抑制Wnt信号通路。
Receptor internalization is recognized as an important mechanism for controlling numerous cell surface receptors. This event contributes not only to regulate signal transduction but also to adjust the amount of cell surface receptors. Frizzleds (Fzds) are seven-pass transmembrane receptor family proteins for Wnt ligands. Recent studies indicated that Fzd5 is internalized in response to Wnt stimulation to activate downstream signaling pathways. After internalization, it appears that Fzd5 is recycled back to the plasma membrane. However, whether internalized Fzd5 is sorted to lysosomes for protein degradation remains unclear. We here report that a coated vesicle-associated kinase of 104 kDa (CVAK104) selectively induces lysosomal degradation of Fzd5. We identify CVAK104 as a novel binding partner of Dishevelled (Dvl), a scaffold protein in the Wnt signaling pathway. Interestingly, we find that CVAK104 also interacts with Fzd5 but not with Fzd1 or Fzd4. CVAK104 selectively induces intracellular accumulation of Fzd5 via the clathrin-mediated pathway, which is suppressed by coexpression of a dominant negative form of Rab5. Fzd5 is subsequently degraded by a lysosomal pathway. Indeed, knockdown of endogenous CVAK104 by RNA interference results in an increase in the amount of Fzd5. In contrast, Wnt treatment induces Fzd5 internalization but does not stimulate its degradation. Overexpression or knockdown of CVAK104 results in a significant suppression or activation of the Wnt/β-catenin pathway, respectively. These results suggest that CVAK104 regulates the amount of Fzd5 by inducing lysosomal degradation, which probably contributes to the suppression of the Wnt signaling pathway.