Leibniz Research Institute for Molecular Pharmacology (FMP) im Forschungsverbund Berlin e.V. (FMP), Berlin, Germany.
NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Berlin, Germany.
Nat Commun. 2022 Aug 10;13(1):4692. doi: 10.1038/s41467-022-32370-5.
Huntington's disease is a neurodegenerative disease caused by an expanded polyQ stretch within Huntingtin (HTT) that renders the protein aggregation-prone, ultimately resulting in the formation of amyloid fibrils. A trimeric chaperone complex composed of Hsc70, DNAJB1 and Apg2 can suppress and reverse the aggregation of HTTExon1Q. DNAJB1 is the rate-limiting chaperone and we have here identified and characterized the binding interface between DNAJB1 and HTTExon1Q. DNAJB1 exhibits a HTT binding motif (HBM) in the hinge region between C-terminal domains (CTD) I and II and binds to the polyQ-adjacent proline rich domain (PRD) of soluble as well as aggregated HTT. The PRD of HTT represents an additional binding site for chaperones. Mutation of the highly conserved H244 of the HBM of DNAJB1 completely abrogates the suppression and disaggregation of HTT fibrils by the trimeric chaperone complex. Notably, this mutation does not affect the binding and remodeling of any other protein substrate, suggesting that the HBM of DNAJB1 is a specific interaction site for HTT. Overexpression of wt DNAJB1, but not of DNAJB1 can prevent the accumulation of HTTExon1Q aggregates in HEK293 cells, thus validating the biological significance of the HBM within DNAJB1.
亨廷顿病是一种神经退行性疾病，由亨廷顿蛋白（HTT）内扩展的多聚谷氨酰胺链引起，使蛋白质易于聚集，最终导致淀粉样纤维的形成。由 Hsc70、DNAJB1 和 Apg2 组成的三聚体伴侣复合物可以抑制和逆转 HTTExon1Q 的聚集。DNAJB1 是限速伴侣，我们在这里鉴定并描述了 DNAJB1 和 HTTExon1Q 之间的结合界面。DNAJB1 在 C 端结构域（CTD）I 和 II 之间的铰链区域具有 HTT 结合基序（HBM），并与可溶性和聚集的 HTT 的多聚 Q 相邻脯氨酸丰富结构域（PRD）结合。HTT 的 PRD 代表伴侣蛋白的另一个结合位点。DNAJB1 的 HBM 中高度保守的 H244 突变完全消除了三聚体伴侣复合物对 HTT 纤维的抑制和去聚集作用。值得注意的是，这种突变不影响任何其他蛋白质底物的结合和重塑，这表明 DNAJB1 的 HBM 是 HTT 的特定相互作用位点。wt DNAJB1 的过表达，但不是 DNAJB1 可以防止 HEK293 细胞中 HTTExon1Q 聚集体的积累，从而验证了 DNAJB1 内 HBM 的生物学意义。
