To decipher the function(s) of HYPK, a huntingtin (HTT)-interacting protein with chaperone-like activity, we had previously identified 36 novel interacting partners of HYPK. Another 13 proteins were known earlier to be associated with HYPK. On the basis of analysis of the interacting partners of HYPK, it has been shown that HYPK may participate in diverse cellular functions relevant to Huntington's disease. In the present study, we identified additional 5 proteins by co-immunoprecipitation and co-localization. As of now we have 54 primary interactors of HYPK. From the database we collected 1026 unique proteins (secondary interactors) interacting with these 54 primary HYPK interacting partners. We observed that 10 primary and 91 secondary interacting proteins of HYPK are associated with two types of autophagy processes. We next tested the hypothesis that the hub, HYPK, might itself be involved in autophagy. Using mouse striatal STHdh(Q7)/Hdh(Q7) cell lines, we observed that over expression of HYPK significantly increased background cellular autophagy, while knock down of endogenous HYPK decreased the autophagy level as detected by altered LC3I conversion, BECN1 expression, cleavage of GFP from LC3-GFP, ATG5-ATG12 conjugate formation and expression of transcription factors like Tfeb, Srebp2 and Zkscan3. This result shows that HYPK, possibly with its interacting partners, induces autophagy. We further observed that N-terminal mutant HTT reduced the cellular levels of LC3II and BECN1, which could be recovered significantly upon over expression of HYPK in these cells. This result further confirms that HYPK could also be involved in clearing mutant HTT aggregates by augmenting autophagy pathway.

中文翻译：

---

伴侣蛋白HYPK及其相互作用的伴侣增强自噬。

为了破译HYPK的功能，一种具有伴侣样活性的亨廷顿蛋白（HTT）相互作用蛋白，我们以前已经确定了36种新型的HYPK相互作用伴侣。早先已知另外13种蛋白与HYPK相关。在对HYPK相互作用伙伴的分析的基础上，已经表明HYPK可能参与与亨廷顿氏病有关的多种细胞功能。在本研究中，我们通过共免疫沉淀和共定位鉴定了另外5种蛋白质。截至目前，我们有54个HYPK的主要相互作用者。从数据库中，我们收集了与这54个主要HYPK相互作用伙伴相互作用的1026种独特蛋白质（第二种相互作用物）。我们观察到，HYPK的10个主要相互作用蛋白和91个次要相互作用蛋白与两种自噬过程相关。接下来，我们检验了枢纽HYPK本身可能参与自噬的假说。使用小鼠纹状体STHdh（Q7）/ Hdh（Q7）细胞系，我们观察到HYPK的过表达显着增加了背景细胞自噬，而敲除内源性HYPK则降低了自噬水平，这是通过改变LC3I转化，BECN1表达，裂解来自LC3-GFP的GFP，ATG5-ATG12共轭物的形成以及转录因子如Tfeb，Srebp2和Zkscan3的表达。该结果表明，HYPK，可能与其相互作用的伴侣，诱导自噬。我们进一步观察到，N末端突变体HTT降低了LC3II和BECN1的细胞水平，当这些细胞中HYPK过表达时，它们可以显着恢复。