Block Samuel, Chi Fangtao, Rosen Paul C, Pineda S Sebastian, Darnell Alicia M, Abbott Keene L, Pena Izabella A, Heiman Myriam, Yilmaz Ömer H, Kory Nora, Vander Heiden Matthew G
David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge, MA, USA.
Department of Biology, MIT, Cambridge, MA, USA.
bioRxiv. 2025 Jul 2:2025.06.18.660357. doi: 10.1101/2025.06.18.660357.
Mitochondria contribute to compartmentalized metabolism in eukaryotic cells, supporting key enzymatic reactions for cell function and energy homeostasis. However, this compartmentalization necessitates regulated metabolite transport across mitochondrial membranes. Although many transport proteins have been identified, several mitochondrial amino acid transporters remain largely uncharacterized. Using CRISPR-Cas9-mediated candidate transporter knockouts coupled with assessment of metabolite transport via a mitochondrial swelling assay, we identify SFXN1, previously characterized for its role in mitochondrial serine transport, as a protein that mediates mitochondrial transport of a range of other polar neutral amino acids including proline, glycine, threonine, taurine, hypotaurine, β-alanine, and γ-aminobutyric acid (GABA). Furthermore, the SFXN1 paralogues SFXN2 and SFXN3 partially complement loss of SFXN1 to enable glycine transport, while SFXN2 and SFXN5 partially complement loss of SFXN1 to enable GABA transport. Altogether, these data suggest that sideroflexins facilitate the transport of polar neutral amino acids across the inner mitochondrial membrane.
线粒体有助于真核细胞中的区室化代谢，支持细胞功能和能量稳态的关键酶促反应。然而，这种区室化需要调节代谢物跨线粒体膜的运输。尽管已经鉴定出许多转运蛋白，但几种线粒体氨基酸转运蛋白在很大程度上仍未得到充分表征。利用CRISPR-Cas9介导的候选转运蛋白敲除技术，并通过线粒体肿胀试验评估代谢物运输，我们确定了SFXN1（此前已证明其在线粒体丝氨酸运输中的作用）是一种介导一系列其他极性中性氨基酸（包括脯氨酸、甘氨酸、苏氨酸、牛磺酸、次牛磺酸、β-丙氨酸和γ-氨基丁酸（GABA））跨线粒体运输的蛋白。此外，SFXN1的旁系同源物SFXN2和SFXN3部分弥补了SFXN1缺失，从而实现甘氨酸运输，而SFXN2和SFXN5部分弥补了SFXN1缺失，从而实现GABA运输。总之，这些数据表明，铁弯曲蛋白有助于极性中性氨基酸跨线粒体内膜的运输。
