Studying Barth syndrome's pathomechanism using high throughput screens in yeast Diana Antunes1, Nofar Harpaz2, Maya Schuldiner2, Doron Rapaport1* 1Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen 72076, Germany 2Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel * email@example.com
Tafazzin is a mitochondrial protein that is involved in the metabolism of cardiolipin (CL) by functioning as a phospholipid-lysophospholipid transacylase. Mutations in the tafazzin gene are associated with a number of clinical disorders including Barth syndrome (BTHS). The tafazzin gene is highly conserved from yeast to human. Deletion of the yeast orthologue TAZ1 results in a decrease in the total cellular amounts of CL, increased levels of monolyso CL (MLCL), and compromised functions of mitochondria. Similar alterations were also observed in fibroblasts and platelets from patients with BTHS or from animal models. Currently, the biochemical mechanisms underlying the mitochondrial dysfunction in BTHS remain uncharacterized. To study the cellular effect of losing Taz1 activity, we performed a high throughput screen employing GFP-fusion variants of the whole yeast proteome and analyzed changes in protein localization and detection levels upon the deletion of TAZ1. Furthermore, we screened for multi-copy suppressors of the taz1Δ growth defect. The visual screens identified several proteins that their subcellular localization or detection levels were altered in the absence of Taz1. Importantly, we identified the branched-chain amino acid transaminases (BCATs), Bat1 and Bat2 as multicopy suppressors of the taz1Δ growth defect. Surprisingly, overexpression of Bat1 or Bat2 does not restore the reduced membrane potential, the altered stability of respiratory chain complexes, and the defective accumulation of MLCL species in cells devoid of Taz1. Hence, our findings suggest that the metabolism of amino acids has an important role in cells lacking Taz1 function and thus shed new light on the pathomechanism of the Barth syndrome.
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