Functional coupling of presequence processing and degradation in human mitochondria
Functional coupling of presequence processing and degradation in human mitochondria
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DOI：
10.1111/febs.15358
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发表时间：
2020-06-03
期刊：
影响因子：
5.4
通讯作者：
Voegtle, Friederike-Nora
中科院分区：
文献类型：
--
作者：
Kuecuekkoese, Cansu;Taskin, Asli Aras;Voegtle, Friederike-Nora
线粒体蛋白质组主要通过输入核编码的前体蛋白来构建和维持。这些前体中的大多数使用N-末端前序列作为被线粒体基质蛋白酶去除的靶向信号。必需的线粒体加工蛋白酶MPP在输入到细胞器后切割前序列，从而使蛋白质折叠和功能成为可能。切割的前序列随后被肽酶降解。虽然这些过程中的大多数已经在酵母中发现，但人类酶的表征仍然很少。由于已报道基质前序列肽酶PreP在阿尔茨海默病中起作用，因此对人类细胞中受损肽周转的分析具有巨大的兴趣。在这里，我们报告HEK 293 T PreP敲除细胞的表征。PreP的缺失导致氧化磷酸化的严重缺陷和应激反应标记基因的核表达的变化。缺乏PreP时的线粒体缺陷是由前序列肽的积累引起的，前序列肽触发MPP的反馈抑制和未加工前体蛋白的积累。此外，在MPP加工后从前体的子集切割八个残基的线粒体中间肽酶MIP在PreP损失后受损，表明PreP也降解MIP产生的八肽。对与神经系统疾病相关的PreP（R183 Q）患者突变的研究表明，该突变使蛋白质不稳定，使其在热休克时易于增强降解和聚集。两者合计，我们的数据揭示了MPP和MIP的前体加工和PreP在人类线粒体中的前序列降解之间的功能耦合，这对维持功能性细胞器蛋白质组至关重要。
The mitochondrial proteome is built and maintained mainly by import of nuclear-encoded precursor proteins. Most of these precursors use N-terminal presequences as targeting signals that are removed by mitochondrial matrix proteases. The essential mitochondrial processing protease MPP cleaves presequences after import into the organelle thereby enabling protein folding and functionality. The cleaved presequences are subsequently degraded by peptidases. While most of these processes have been discovered in yeast, characterization of the human enzymes is still scarce. As the matrix presequence peptidase PreP has been reported to play a role in Alzheimer's disease, analysis of impaired peptide turnover in human cells is of huge interest. Here, we report the characterization of HEK293T PreP knockout cells. Loss of PreP causes severe defects in oxidative phosphorylation and changes in nuclear expression of stress response marker genes. The mitochondrial defects upon lack of PreP result from the accumulation of presequence peptides that trigger feedback inhibition of MPP and accumulation of nonprocessed precursor proteins. Also, the mitochondrial intermediate peptidase MIP that cleaves eight residues from a subset of precursors after MPP processing is compromised upon loss of PreP suggesting that PreP also degrades MIP generated octapeptides. Investigation of the PreP(R183Q) patient mutation associated with neurological disorders revealed that the mutation destabilizes the protein making it susceptible to enhanced degradation and aggregation upon heat shock. Taken together, our data reveal a functional coupling between precursor processing by MPP and MIP and presequence degradation by PreP in human mitochondria that is crucial to maintain a functional organellar proteome.