The cytosolic cochaperone Sti1 is relevant for mitochondrial biogenesis and morphology. (28th July 2016)

• Record Type: Journal Article
• Authors: Hoseini, Hoda; Pandey, Saroj; Jores, Tobias; Schmitt, Anja; Franz‐Wachtel, Mirita; Macek, Boris; Buchner, Johannes; Dimmer, Kai Stefan; Rapaport, Doron
• Is Part Of: FEBS journal. Volume 283:Number 18(2016)
• Page Start: 3338
• Page End: 3352
• Publication Date: 2016-07-28
• Subjects: chaperones -- import receptors -- mitochondria -- protein import -- TOM complex; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.13813
• Languages: English
• ISSNs: 1742-464X

Abstract

Abstract : Most mitochondrial proteins are synthesized in the cytosol prior to their import into the organelle. It is commonly accepted that cytosolic factors are required for delivering precursor proteins to the mitochondrial surface and for keeping newly synthesized proteins in an import‐competent conformation. However, the identity of such factors and their defined contribution to the import process are mostly unknown. Using a presequence‐containing model protein and a site‐directed photo‐crosslinking approach in yeast cells we identified the cytosolic chaperones Hsp70 (Ssa1) and Hsp90 (Hsp82) as well as their cochaperones, Sti1 and Ydj1, as putative cytosolic factors involved in mitochondrial protein import. Deletion of STI1 caused both alterations in mitochondrial morphology and lower steady‐state levels of a subset of mitochondrial proteins. In addition, double deletion of STI1 with the mitochondrial import factors, MIM1 or TOM20, showed a synthetic growth phenotype indicating a genetic interaction of STI1 with these genes. Moreover, recombinant cytosolic domains of the import receptors Tom20 and Tom70 were able to bind in vitro Sti1 and other cytosolic factors. In summary, our observations point to a, direct or indirect, role of Sti1 for mitochondrial functionality. Abstract : Most mitochondrial proteins are synthesized in the cytosol prior to their import into the organelle. We identified the cytosolic chaperones Hsp70 and Hsp90 as well as their cochaperones, Sti1 and Ydj1, as factors involved in mitochondrial protein import. Deletion of STI1 caused alterations in mitochondrial morphology and biogenesis, and the protein appears to play a role in mitochondrial functionality.