Yi Jae Kyo, Xu Ruijuan, Jeong Eunmi, Mileva Izolda, Truman Jean-Philip, Lin Chih-Li, Wang Kai, Snider Justin, Wen Sally, Obeid Lina M, Hannun Yusuf A, Mao Cungui
Graduate Program in Molecular and Cellular Biology, Stony Brook University, Stony Brook, NY, USA.
Department of Medicine, Stony Brook University, Stony Brook, NY, USA.
Oncotarget. 2016 Apr 19;7(16):21124-44. doi: 10.18632/oncotarget.8195.
Sphingoid bases (SBs) as bioactive sphingolipids, have been implicated in aging in yeast. However, we know neither how SBs are regulated during yeast aging nor how they, in turn, regulate it. Herein, we demonstrate that the yeast alkaline ceramidases (YPC1 and YDC1) and SB kinases (LCB4 and LCB5) cooperate in regulating SBs during the aging process and that SBs shortens chronological life span (CLS) by compromising mitochondrial functions. With a lipidomics approach, we found that SBs were increased in a time-dependent manner during yeast aging. We also demonstrated that among the enzymes known for being responsible for the metabolism of SBs, YPC1 was upregulated whereas LCB4/5 were downregulated in the course of aging. This inverse regulation of YPC1 and LCB4/5 led to the aging-related upregulation of SBs in yeast and a reduction in CLS. With the proteomics-based approach (SILAC), we revealed that increased SBs altered the levels of proteins related to mitochondria. Further mechanistic studies demonstrated that increased SBs inhibited mitochondrial fusion and caused fragmentation, resulting in decreases in mtDNA copy numbers, ATP levels, mitochondrial membrane potentials, and oxygen consumption. Taken together, these results suggest that increased SBs mediate the aging process by impairing mitochondrial structural integrity and functions.
鞘氨醇碱（SBs）作为生物活性鞘脂，与酵母衰老有关。然而，我们既不知道酵母衰老过程中SBs是如何被调控的，也不知道它们又是如何反过来调控衰老的。在此，我们证明酵母碱性神经酰胺酶（YPC1和YDC1）和SB激酶（LCB4和LCB5）在衰老过程中协同调控SBs，并且SBs通过损害线粒体功能缩短了时序寿命（CLS）。通过脂质组学方法，我们发现酵母衰老过程中SBs以时间依赖性方式增加。我们还证明，在已知负责SBs代谢的酶中，YPC1在衰老过程中上调，而LCB4/5下调。YPC1和LCB4/5的这种反向调控导致酵母中与衰老相关的SBs上调以及CLS降低。通过基于蛋白质组学的方法（SILAC），我们揭示增加的SBs改变了与线粒体相关的蛋白质水平。进一步的机制研究表明，增加的SBs抑制线粒体融合并导致碎片化，从而导致mtDNA拷贝数、ATP水平、线粒体膜电位和氧消耗降低。综上所述，这些结果表明增加的SBs通过损害线粒体结构完整性和功能来介导衰老过程。
