Broad Institute, Cambridge, Massachusetts, USA; Department of Molecular Biology, Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts, USA; Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, USA.
Broad Institute, Cambridge, Massachusetts, USA; Department of Molecular Biology, Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts, USA; Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, USA.
J Biol Chem. 2023 Sep;299(9):105075. doi: 10.1016/j.jbc.2023.105075. Epub 2023 Jul 20.
Iron-sulfur clusters (ISC) are essential cofactors that participate in electron transfer, environmental sensing, and catalysis. Amongst the most ancient ISC-containing proteins are the ferredoxin (FDX) family of electron carriers. Humans have two FDXs- FDX1 and FDX2, both of which are localized to mitochondria, and the latter of which is itself important for ISC synthesis. We have previously shown that hypoxia can eliminate the requirement for some components of the ISC biosynthetic pathway, but FDXs were not included in that study. Here, we report that FDX1, but not FDX2, is dispensable under 1% O in cultured human cells. We find that FDX1 is essential for production of the lipoic acid cofactor, which is synthesized by the ISC-containing enzyme lipoyl synthase. While hypoxia can rescue the growth phenotype of either FDX1 or lipoyl synthase KO cells, lipoylation in these same cells is not rescued, arguing against an alternative biosynthetic route or salvage pathway for lipoate in hypoxia. Our work reveals the divergent roles of FDX1 and FDX2 in mitochondria, identifies a role for FDX1 in lipoate synthesis, and suggests that loss of lipoic acid can be tolerated under low oxygen tensions in cell culture.
铁硫簇（ISC）是参与电子传递、环境感应和催化的必需辅因子。在最古老的含有 ISC 的蛋白质中，有一类是电子载体的铁氧还蛋白（FDX）家族。人类有两种 FDX-FDX1 和 FDX2，它们都定位于线粒体，后者本身对 ISC 的合成很重要。我们之前的研究表明，缺氧可以消除 ISC 生物合成途径的一些成分的需求，但该研究不包括 FDX。在这里，我们报告说，在培养的人类细胞中，FDX1 而不是 FDX2 在 1%O 下是可有可无的。我们发现 FDX1 对于脂酰基辅酶 A 的合成是必需的，而脂酰基辅酶 A 是由含有 ISC 的酶脂酰基辅酶合成酶合成的。虽然缺氧可以挽救 FDX1 或脂酰基辅酶合成酶 KO 细胞的生长表型，但这些相同细胞中的脂酰化没有得到挽救，这表明在缺氧条件下，脂酰基辅酶 A 没有替代生物合成途径或补救途径。我们的工作揭示了 FDX1 和 FDX2 在线粒体中的不同作用，确定了 FDX1 在脂酰基辅酶 A 合成中的作用，并表明在细胞培养中低氧张力下可以耐受失去脂酰基辅酶 A。
