Mitophagy Dependent Regulation of Mammary Gland Differentiation

摘要 线粒体通过感知和响应细胞，作为许多新陈代谢过程的中心枢纽 维持动态平衡的环境。因此，它们的破坏是发病和进展的关键因素。 许多人类疾病，包括代谢紊乱、神经退行性疾病和癌症。 线粒体的动态平衡主要是通过靶向回收受损的线粒体来维持的 自噬，称为有丝分裂吞噬。有丝分裂是组织特有的，发生在对细胞应激和 差异化提示。分化提示的有丝分裂吞噬通常被称为程序性有丝分裂吞噬 因其对表观遗传状态、细胞命运决定、代谢适应和 差异化。尽管这些影响和其他影响都被归因于吞丝分裂，但人们对这种作用知之甚少 上游信号通路诱导有丝分裂，以满足特定的细胞需求。独特的形态 在出生后的乳腺发育阶段，线粒体存在差异。这表明 有丝分裂对这种组织的发育起着重要的作用。确定通过哪些机制 在乳腺发育过程中维持线粒体动态平衡将提供急需的洞察力 线粒体适应在正常发育和疾病中的更广泛作用。我们已经证明了 SIM2s(SIM2s，来源于SIM2)在乳腺发育过程中差异表达 是功能性乳腺分化的关键调节因子。我们最新的结果是利用乳腺- 特异的高表达和低表达的Sim2s转基因小鼠表明SIM2s是功能性哺乳所必需的， 并且部分地通过与PRKN有丝分裂复合体的直接相互作用来做到这一点。根据这些新的结果， 我们假设依赖有丝分裂的线粒体适应对乳腺功能是必不可少的。 SIM2s是维持线粒体动态平衡所必需的。为了解决这一假设，我们 提出两个具体目标。在目标1中，我们将确定所需的有丝分裂驱动的代谢转变 MMTV-Sim2s和Sim2fl/fl与MMTV-QC小鼠模型杂交诱导乳腺上皮细胞分化 以评估小鼠的有丝分裂和线粒体结构以及代谢适应。在目标2中，我们将定义 SIM2、ATM、PINK1/PRKN和LC3之间相互作用的物理基础和功能结果 有丝分裂与乳腺分化。该提案的成功完成将提供对 到目前为止，线粒体在生理条件下的适应机制尚不清楚。我们期待结果 这些研究将有助于确定线粒体在乳腺发育中的适应机制， 哺乳和癌症。

SUMMARY Mitochondria operate as a central hub for many metabolic processes by sensing and responding to the cellular environment to maintain homeostasis. Consequently, their disruption is a key factor in the onset and progression of many human conditions, including metabolic disorders, neurodegenerative diseases, and cancer. Mitochondrial homeostasis is primarily maintained through the recycling of damaged mitochondria by targeted autophagy, termed mitophagy. Mitophagy is tissue-specific and occurs in response to both cellular stress and differentiation cues. Differentiation-cued mitophagy is often termed programmed mitophagy and has recently gained attention for its contribution to epigenetic status, cell fate decisions, metabolic adaptation and differentiation. Although these and other effects have been attributed to mitophagy, little is known about the upstream signaling pathways that induce mitophagy to meet specific cellular needs. Distinct morphological differences in mitochondria exist during the post-natal stages of mammary gland development. This suggests that mitophagy plays an important to the development of this tissue. Identifying the mechanism by which mitochondrial homeostasis is maintained during mammary gland development will provide much needed insight into the broader role of mitochondrial adaptation in normal development and disease. We have shown that Singleminded-2s (SIM2s; expressed from Sim2), is differentially expressed during mammary gland development and is a key regulator of functional mammary gland differentiation. Our recent results utilizing mammary gland- specific over- and under-expressing Sim2s transgenic mice show that SIM2s is required for functional lactation, and does so, in part, through direct interaction with the PRKN mitophagy complex. Based on these new results, we hypothesize that mitophagy-dependent mitochondrial adaptation is essential for mammary gland functional differentiation and that SIM2s is required to maintain mitochondrial homeostasis. To address this hypothesis we propose two Specific Aims. In Aim 1, we will determine the mitophagy-driven metabolic transition required for mammary epithelial cell differentiation by crossing the mito-QC mouse model with MMTV-Sim2s and Sim2fl/fl mice to assess mitophagy and mitochondrial architecture and metabolic adaptation. In Aim 2, we will define the physical basis for, and functional outcomes of, interactions between SIM2s, ATM, PINK1/PRKN, and LC3 in mitophagy and mammary gland differentiation. Successful completion of this proposal will provide insight into heretofore unknown mechanisms of mitochondrial adaptation under physiological conditions. We expect results from these studies will help define the mechanism of mitochondrial adaptation in mammary gland development, lactation, and cancer.