Palmitoylation-dependent massive endocytosis (pMEND)

描述（由申请人提供）：本项目关注线粒体调节细胞质调节蛋白和表面膜转换的新的心脏信号通路。该途径依赖于辅酶A（CoA）通过线粒体积累到高浓度，使得游离CoA到细胞质的梯度大于50：1。由于这个原因，线粒体内膜中的非选择性渗透性转换孔（PTP）的瞬时打开可以在细胞质中产生微摩尔CoA瞬变，而不会显著消耗其他线粒体底物。然后CoA瞬变转化为酰基CoA瞬变，因为酰基CoA合成酶受主要的游离细胞质CoA浓度的限制。许多信号蛋白会受到影响。在极端的代谢应激中，如在缺血性心脏组织的再氧合后发生的，表面膜蛋白经由该途径的棕榈酰化明显导致它们聚集在液体有序（Lo）膜结构域中，随后它们作为大量内吞作用（pMEND）内化。在这种情况下，pMEND是有害的，但初步数据表明，pMEND途径有助于组成性肌膜周转和调节心肌细胞中的Na/K泵的活性。使用多个在这一途径中存在缺陷的小鼠品系，以及阻断PTP的药物，我们将确定pMEND相关的内吞作用在心肌细胞中起什么样的生理和病理作用。该项目将提供对基本细胞调控机制的深入了解，这些机制对了解发达国家的主要死亡原因具有重要影响。

DESCRIPTION (provided by applicant): This project focuses on a new cardiac signaling pathway by which mitochondria regulate cytoplasmic regulatory proteins and surface membrane turnover. The pathway relies on the accumulation by mitochondria of coenzyme A (CoA) to a high concentration, such that free CoA gradients to the cytoplasm are greater than 50 to1. For this reason, transient openings of nonselective permeability transition pores (PTP's) in the inner mitochondrial membrane can generate micromolar CoA transients in the cytoplasm without significantly depleting other mitochondrial substrates. CoA transients are then converted to acyl CoA transients because acyl CoA sythetases are limited by the prevailing free cytoplasmic CoA concentration. Numerous signaling proteins will be affected. In extreme metabolic stress, as occurs upon reoxygenation of ischemic cardiac tissue, palmitoylation of surface membrane proteins via this pathway evidently leads to their clustering in liquid ordered (Lo) membrane domains followed by their internalization as massive endocytosis (pMEND). In this context pMEND is detrimental, but preliminary data indicate that the pMEND pathway contributes to constitutive sarcolemma turnover and regulates the activities of Na/K pumps in cardiac myocytes. Using multiple mice lines with deficiencies in this pathway, as well as drugs to block PTP's, we will determine what physiological and pathological roles pMEND-related endocytosis plays in cardiac myocytes. The project will provide insight into fundamental cell regulatory mechanisms that have a high impact for an understanding of the leading cause of death in the developed world.