Mitochondrial inheritance and quality control

蛋白质稳态，或蛋白质稳态，依赖于对蛋白质合成、折叠和降解的精确控制。 前列腺癌错误会导致蛋白质聚集，这种聚集是有毒的，并与神经退行性疾病、心血管疾病、 肌肉和新陈代谢障碍，以及过早衰老。内质网和线粒体是蛋白质的主要部位 折叠，并由质量控制机制支持，以纠正蛋白质折叠或消除蛋白质或 细胞器受损，无法修复。内质网相关降解(ERAD)与线粒体相关 降解(MAD)是与功能和机械相关的机制。在这两种情况下，错误折叠的蛋白质 鉴定，泛素化，从细胞器中提取，并被蛋白酶体降解。然而，这两条路径 都有局限性。以往的研究表明，MAD蛋白抑制作用仅限于线粒体外膜-- 膜(OM)蛋白，占线粒体蛋白的10%。此外，MAD和ERAD本身就是低吞吐量的 因为它们作用于单个蛋白质。这种限制对内质网来说是一个特别令人担忧的问题，在内质网中，所有蛋白质的三分之一 细胞经历折叠，蛋白质以每分钟0.1-100万蛋白质的速度进入内质网。在最后一次 资助期，我们发现MAD在线粒体基质和内膜的蛋白抑制调控中发挥作用 蛋白质。与此一致，我们发现MAD而不是伴侣、蛋白酶或自噬蛋白发挥作用 线粒体和细胞适合性在衰老模型中的主要作用以及MAD功能的丧失导致 过早衰老。我们还在体外重组了MAD底物从基质中的逆转录移位，并鉴定了它的存在。 TOM通道将蛋白质输入线粒体，在MAD底物的逆转位中扮演了重要角色 从细胞器里出来。在互补性研究中，我们发现了一条新的ER蛋白平衡途径，该途径有重叠- PING与ERAD一起发挥作用，但具有较高的吞吐能力，有助于酵母的内质网应激反应。 新发现的先天性肌营养不良症(CHKB CMD)的马里细胞和细胞模型。在这条道路上- 通过这种方式，内质网膜上形成的细胞器--脂滴(LD)--可以作为大规模清除的逃生通道 未折叠的内质网蛋白和这些蛋白及其LD载体的降解。在这里，退化发生在 微自噬，一种保守但未被研究的自噬形式，不依赖于自噬小体或核心 将货物运送到液泡(酵母溶酶体)的ATG基因。相反，学习记忆障碍是通过直接接触发生的 随着液泡在液泡膜的凹陷处，LDS被释放到液泡腔 运输所需的内体分选复合体(ESCRT)介导的膜断裂。重要的功夫- 真正的目标是了解线粒体内MAD功能的机制，以及MAD的生理意义。 MAD介导的线粒体蛋白平衡的序列。另一个重要目标是识别组件和 ESCRT和微脂细胞介导的ER蛋白稳定途径ER-PERM的功能后果 AGY，在酵母和哺乳动物细胞中。这些研究将揭示ER-PERM和靶点的机制和功能 用于治疗CHKB CMD，这是一种威胁生命的疾病，目前尚无治愈方法。

Protein homeostasis, or proteostasis, relies on precise control of protein synthesis, folding and degradation. Proteostatic errors lead to protein aggregates, which are toxic and linked to neurodegenerative, cardiovascular, muscular and metabolic disorders, and to premature aging. The ER and mitochondria are major sites for protein folding and are supported by quality control mechanisms that correct protein folding or eliminate proteins or organelles that are damaged beyond repair. ER-associated degradation (ERAD) and mitochondria-associated degradation (MAD) are functionally and mechanistically related mechanisms. In both, misfolded proteins are identified, ubiquitinated, extracted from organelles and degraded by the proteasome. However, both pathways have limitations. Previous studies suggested that MAD proteostasis was restricted to mitochondrial outer mem- brane (OM) proteins, <10% of mitochondrial proteins. Moreover, MAD and ERAD are inherently low-throughput because they act on individual proteins. This limitation is a particular concern for ER, where 1/3 of all proteins in the cell undergo folding, and protein entry into ER occurs at rates of 0.1-1 million proteins/minute. In the last funding period, we found that MAD functions in proteostatic control of mitochondrial matrix and inner membrane proteins. Consistent with this, we found that MAD and not chaperones, proteases or autophagy proteins, plays a major role in mitochondrial and cellular fitness in a model for aging and that loss of MAD function results in premature aging. We also reconstituted retrotranslocation of MAD substrates from the matrix in vitro and identi- fied a role for the TOM channel, which imports proteins into mitochondria, in retrotranslocation of MAD substrates out of the organelle. In complementary studies, we identified a novel ER proteostasis pathway that has overlap- ping function with ERAD, but has higher throughput and contributes to the ER stress response in yeast, mam- malian cells and cellular models for a newly identified congenital muscular dystrophy (CHKB CMD). In this path- way, lipid droplets (LDs), organelles that form at ER membranes, act as escape hatches for large-scale removal of unfolded ER proteins and degradation of those proteins and their LD carriers. Here, degradation occurs by microautophagy, a conserved but understudied form of autophagy that does not rely on autophagosomes or core ATG genes for delivery of cargoes to the vacuole (yeast lysosome). Rather, LD uptake occurs by direct contact with the vacuole at invaginations of the vacuolar membrane, and LDs are released into the vacuolar lumen by membrane scission mediated by the endosomal sorting complex required for transport (ESCRT). Important fu- ture goals are to understand the mechanism of MAD function within mitochondria, and the physiological conse- quences of MAD-mediated mitochondrial proteostasis. Another important goal is to identify components and functional consequences of ER-PERM, the pathway for ER proteostasis mediated by ESCRT and microlipoph- agy, in yeast and mammalian cells. These studies will reveal mechanisms and functions of ER-PERM and targets for treatment of CHKB CMD, a life-threatening disease for which there is no cure.