Mdm20 stimulates polyQ aggregation via inhibiting autophagy through Akt-Ser473 phosphorylation.
Mdm20 stimulates polyQ aggregation via inhibiting autophagy through Akt-Ser473 phosphorylation.
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DOI：
10.1371/journal.pone.0082523
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Mori N
中科院分区：
文献类型：
--
作者：
Yasuda K;Ohyama K;Onga K;Kakizuka A;Mori N
Mdm 20是NatB复合物的辅助亚基，其包括蛋白质N-末端乙酰化的催化亚基Nat 5。NatB复合物在从头蛋白质合成起始期间催化N-乙酰化;然而，最近来自酵母的证据表明NatB还影响原肌球蛋白的翻译后修饰，其参与聚集蛋白的细胞内分选。我们假设乙酰化复合物如NatB可能有助于哺乳动物细胞中的蛋白质清除和/或蛋白质稳态。使用聚谷氨酰胺（polyQ）聚集系统，我们研究了是否NatB复合物或其成分影响蛋白质聚集在大鼠原代培养的海马神经元和HEK 293细胞。PolyQ聚集体的数量在Mdm 20过表达（OE）细胞中增加，但在Nat 5-OE细胞中不增加。相反，在Mdm 20敲低（KD）细胞中，而不是在Nat 5-KD细胞中，polyQ聚集显著减少。尽管Mdm 20直接与Nat 5结合，但两种蛋白质的总体细胞定位略有不同，并且Mdm 20显然与polyQ聚集体共定位。此外，在Mdm 20-KD细胞中，LC 3的点状外观是明显的，表明诱导自噬。与这一观点一致，Akt的磷酸化，最显著的是在Ser 473，在Mdm 20-KD细胞中大大减少。这些结果表明，Mdm 20，即所谓的辅助亚基的抑制偶联蛋白N-乙酰化复合物，有助于蛋白质清除和/或聚集体的形成，通过影响Akt的磷酸化水平独立于Nat 5的功能。
Mdm20 is an auxiliary subunit of the NatB complex, which includes Nat5, the catalytic subunit for protein N-terminal acetylation. The NatB complex catalyzes N-acetylation during de novo protein synthesis initiation; however, recent evidence from yeast suggests that NatB also affects post-translational modification of tropomyosin, which is involved in intracellular sorting of aggregated proteins. We hypothesized that an acetylation complex such as NatB may contribute to protein clearance and/or proteostasis in mammalian cells. Using a poly glutamine (polyQ) aggregation system, we examined whether the NatB complex or its components affect protein aggregation in rat primary cultured hippocampal neurons and HEK293 cells. The number of polyQ aggregates increased in Mdm20 over-expressing (OE) cells, but not in Nat5-OE cells. Conversely, in Mdm20 knockdown (KD) cells, but not in Nat5-KD cells, polyQ aggregation was significantly reduced. Although Mdm20 directly associates with Nat5, the overall cellular localization of the two proteins was slightly distinct, and Mdm20 apparently co-localized with the polyQ aggregates. Furthermore, in Mdm20-KD cells, a punctate appearance of LC3 was evident, suggesting the induction of autophagy. Consistent with this notion, phosphorylation of Akt, most notably at Ser473, was greatly reduced in Mdm20-KD cells. These results demonstrate that Mdm20, the so-called auxiliary subunit of the translation-coupled protein N-acetylation complex, contributes to protein clearance and/or aggregate formation by affecting the phosphorylation level of Akt indepenently from the function of Nat5.
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影响因子：
56.9
作者：
Choudhary, Chunaram;Kumar, Chanchal;Mann, Matthias
通讯作者：
Mann, Matthias
影响因子：
4.8
作者：
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Li, BY
影响因子：
64.8
作者：
Hubbert, C;Guardiola, A;Yao, TP
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Yao, TP
影响因子：
4.4
作者：
Helbig AO;Rosati S;Pijnappel PW;van Breukelen B;Timmers MH;Mohammed S;Slijper M;Heck AJ
通讯作者：
Heck AJ
影响因子：
3.7
作者：
Bobrowska A;Donmez G;Weiss A;Guarente L;Bates G
通讯作者：
Bates G