Massive palmitoylation-dependent endocytosis during reoxygenation of anoxic cardiac muscle.
Massive palmitoylation-dependent endocytosis during reoxygenation of anoxic cardiac muscle.
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DOI：
10.7554/elife.01295
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发表时间：
2013-11-26
期刊：
影响因子：
7.7
通讯作者：
Hilgemann DW
中科院分区：
文献类型：
--
作者：
Lin MJ;Fine M;Lu JY;Hofmann SL;Frazier G;Hilgemann DW
在成纤维细胞中，大的Ca瞬变激活大量内吞作用（MEND），其涉及线粒体通透性转换孔（PTP）开口之后的膜蛋白棕榈酰化。在这里，我们描述了心肌中的这一通路。具有酰基转移酶DHHC 5表达增加的肌细胞具有降低的Na/K泵活性。在DHHC 5缺乏的心肌细胞中，Na/K泵活性和表面积/体积比增加，棕榈酰化调节蛋白磷脂酶原（PLM）和心脏Na/Ca交换器（NCX 1）显示出更大的表面膜定位，四种方案中MEND被抑制。电学和光学方法都表明，PTP依赖的MEND发生在缺氧心脏的复氧过程中。缺氧后MEND在DHHC 5缺乏的心脏中被消融，被环孢菌素A（CsA）和腺苷抑制，被星形孢菌素（STS）促进，在缺乏PLM的心脏中减少，并且与缺氧后收缩功能受损相关。因此，MEND途径似乎是有害的，在严重的氧化应激，但可能组成性地有助于依赖于代谢应激的心脏肌膜周转。DOI：http://dx.doi.org/10.7554/eLife.01295.001许多中风或心脏病发作后幸存下来的人在血液供应恢复时会经历严重的组织损伤。大部分这种损害可能是由细胞内的线粒体释放一种称为细胞色素c的蛋白质引起的，这种蛋白质可以导致细胞在一个称为凋亡的过程中死亡。当线粒体的外膜变得可渗透时，细胞色素c被释放，并且称为渗透性转换孔的孔在内膜中打开。现在，Lin等人探索在缺氧组织的复氧过程中，线粒体释放的其他分子是否也可能引发重要的细胞反应。Lin及其同事最近表明，某些细胞的线粒体可以释放一种小的酶辅因子辅酶A，然后促进称为大规模内吞作用的细胞反应。这个过程可以导致高达70%的细胞表面膜以膜囊泡的形式被吸收到细胞内部。大多数形式的内吞作用涉及细胞膜的小得多的部分，并采用一组不参与大量内吞作用的众所周知的内吞蛋白。现在，Lin等人研究了大量内吞作用在心肌中的作用。电学和光学测量结果显示，大量的内吞作用发生在缺氧的心肌细胞重新供氧时。Lin等人还发现，必须存在一种称为DHHC 5的酶才能在复氧期间发生内吞作用。DHHC 5是一种酶，催化一种称为酰化的过程-酰基转移到细胞表面的蛋白质。此外，DHHC 5的缺失对缺氧后心肌的性能具有有益的影响，这意味着抑制蛋白酰化的分子可能会保护心脏免受再氧合过程中的损伤。总之，这些结果为酰化建立了新的病理和生理作用，酰化是膜蛋白合成后最常见的生化修饰之一。DOI：http://dx.doi.org/10.7554/eLife.01295.002网站
In fibroblasts, large Ca transients activate massive endocytosis (MEND) that involves membrane protein palmitoylation subsequent to mitochondrial permeability transition pore (PTP) openings. Here, we characterize this pathway in cardiac muscle. Myocytes with increased expression of the acyl transferase, DHHC5, have decreased Na/K pump activity. In DHHC5-deficient myocytes, Na/K pump activity and surface area/volume ratios are increased, the palmitoylated regulatory protein, phospholemman (PLM), and the cardiac Na/Ca exchanger (NCX1) show greater surface membrane localization, and MEND is inhibited in four protocols. Both electrical and optical methods demonstrate that PTP-dependent MEND occurs during reoxygenation of anoxic hearts. Post-anoxia MEND is ablated in DHHC5-deficient hearts, inhibited by cyclosporine A (CsA) and adenosine, promoted by staurosporine (STS), reduced in hearts lacking PLM, and correlates with impaired post-anoxia contractile function. Thus, the MEND pathway appears to be deleterious in severe oxidative stress but may constitutively contribute to cardiac sarcolemma turnover in dependence on metabolic stress. DOI: http://dx.doi.org/10.7554/eLife.01295.001 Many people who survive a stroke or heart attack experience substantial tissue damage when the blood supply is restored. Much of this damage can be caused by the mitochondria inside the cells releasing a protein called cytochrome c that can cause cells to die in a process called apoptosis. The cytochrome c is released as the outer membrane of the mitochondria becomes permeable and pores called permeability transition pores open up in the inner membrane. Now Lin et al. explore if additional molecules released from the mitochondria might also initiate important cellular responses during the reoxygenation of oxygen-deprived tissue. Lin and co-workers recently showed that the mitochondria of some cells can release a small enzyme cofactor, coenzyme A, which then promotes a cellular response called massive endocytosis. This process can cause up to 70% of the cell surface membrane to be absorbed into the interior of the cell in the form of membrane vesicles. Most forms of endocytosis involve a much smaller fraction of the cell membrane and employ a set of well-known endocytic proteins that are not involved in massive endocytosis. Now, Lin et al. investigate the role of massive endocytosis in cardiac muscle. Electrical and optical measurements reveal that massive endocytosis occurs as cardiac cells that have been deprived of oxygen are reoxygenated. Lin et al. also find that an enzyme called DHHC5 must be present to allow endocytosis to take place during reoxygenation. DHHC5 is an enzyme that catalyzes a process called acylation – the transfer of acyl groups to proteins at the cell surface. Moreover, the deletion of DHHC5 has a beneficial impact on the performance of cardiac muscle after oxygen deprivation, which implies that molecules that inhibit protein acylation might protect the heart from damage during reoxygenation. Together, these results establish new pathological and physiological roles for the acylation, which is one of the most common biochemical modifications made to membrane proteins after they are synthesized. DOI: http://dx.doi.org/10.7554/eLife.01295.002