Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America.
PLoS One. 2012;7(7):e39428. doi: 10.1371/journal.pone.0039428. Epub 2012 Jul 10.
Magmas is a growth factor responsive gene encoding an essential mitochondrial protein in mammalian cells. Pam16, the Magmas ortholog in Saccharomyces cerevisiae, is a component of the presequence translocase-associated motor. A temperature-sensitive allele (pam16-I61N) was used to query an array of non-essential gene-deletion strains for synthetic genetic interactions. The pam16-I61N mutation at ambient temperature caused synthetic lethal or sick phenotypes with genes involved in lipid metabolism, perixosome synthesis, histone deacetylation and mitochondrial protein import. The gene deletion array was also screened for suppressors of the pam16-I61N growth defect to identify compensatory pathways. Five suppressor genes were identified (SUR4, ISC1, IPT1, SKN1, and FEN1) and all are involved in sphingolipid metabolism. pam16-I61N cells cultured in glucose at non-permissive temperatures resulted in rapid growth inhibition and G1 cell cycle arrest, but cell viability was maintained. Altered mitochondria morphology, reduced peroxisome induction in glycerol/ethanol and oleate, and changes in the levels of several sphingolipids including C18 alpha-hydroxy-phytoceramide, were also observed in the temperature sensitive strain. Deletion of SUR4, the strongest suppressor, reversed the temperature sensitive fermentative growth defect, the morphological changes and the elevated levels of C18 alpha-hydroxy phytoceramide in pam16-I61N. Deletion of the other four suppressor genes had similar effects on C18 alpha-hydroxy-phytoceramide levels and restored proliferation to the pam16-I61N strain. In addition, pam16-I61N inhibited respiratory growth, likely by reducing cardiolipin, which is essential for mitochondrial function. Our results suggest that the pleiotropic effects caused by impaired Pam16/Magmas function are mediated in part by changes in lipid metabolism.
Magmas 是一种生长因子反应性基因，编码哺乳动物细胞中必需的线粒体蛋白。Saccharomyces cerevisiae 中的 Magmas 同源物 Pam16 是前导序列易位酶相关马达的组成部分。使用温度敏感等位基因 (pam16-I61N) 来查询非必需基因缺失菌株的数组，以进行合成遗传相互作用的查询。在环境温度下， pam16-I61N 突变导致与脂质代谢、过氧化物酶体合成、组蛋白去乙酰化和线粒体蛋白导入相关的基因发生合成致死或病态表型。还筛选了基因缺失数组以抑制 pam16-I61N 生长缺陷的抑制子，以鉴定补偿途径。鉴定了五个抑制子基因（SUR4、ISC1、IPT1、SKN1 和 FEN1），它们都参与鞘脂代谢。在非允许温度下用葡萄糖培养 pam16-I61N 细胞会导致快速生长抑制和 G1 细胞周期停滞，但细胞活力得以维持。在温度敏感菌株中还观察到线粒体形态改变、甘油/乙醇和油酸中过氧化物酶体诱导减少以及几种鞘脂水平的变化，包括 C18 alpha-羟基植物神经酰胺。SUR4 的缺失，最强的抑制剂，逆转了 pam16-I61N 的温度敏感发酵生长缺陷、形态变化和 C18 alpha-羟基植物神经酰胺水平的升高。其他四个抑制子基因的缺失对 C18 alpha-羟基植物神经酰胺水平有类似的影响，并恢复了 pam16-I61N 菌株的增殖。此外， pam16-I61N 抑制呼吸生长，可能是通过降低对线粒体功能至关重要的心磷脂。我们的结果表明，Pam16/Magmas 功能受损引起的多效性效应部分是通过脂质代谢的变化介导的。
