Palmitoylation-dependent massive endocytosis (pMEND)

描述（申请人提供）：本项目重点研究线粒体调节细胞质调节蛋白和表面膜转换的一种新的心脏信号通路。该途径依赖于线粒体对辅酶A （CoA）的高浓度积累，使游离CoA向细胞质的梯度大于50比1。因此，线粒体内膜非选择性通透性过渡孔（PTP's）的瞬间打开可以在细胞质中产生微摩尔CoA瞬态，而不会显著消耗其他线粒体底物。瞬时辅酶a随后转化为瞬时酰基辅酶a，因为酰基辅酶a合成酶受到普遍的游离细胞质CoA浓度的限制。许多信号蛋白将受到影响。在极端代谢应激下，如缺血心脏组织再氧化时发生的情况，通过这一途径，表面膜蛋白的棕榈酰化明显导致它们在液体有序（Lo）膜结构域聚集，然后内化为大量内吞作用（pMEND）。在这种情况下，pMEND是有害的，但初步数据表明，pMEND途径有助于构成性肌膜的转换，并调节心肌细胞中Na/K泵的活性。我们将利用该途径缺失的多个小鼠系，以及阻断PTP的药物，确定ppend相关的内吞作用在心肌细胞中所起的生理和病理作用。该项目将提供对基本细胞调节机制的深入了解，这对了解发达国家的主要死亡原因具有重大影响。

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.