Plasma membrane localization of paralogous leucine permeases Bap2 and Bap3 is regulated by Bul1

Abstract

<jats:title>Abstract</jats:title><jats:p>Timeliness in expression and degradation of the nutrient permeases is vital for any organism. In <jats:italic>Saccharomyces cerevisiae</jats:italic> while transcriptional regulation of permeases has been studied in great detail, post translational events such as trafficking, sorting and turnover are poorly understood. We observed that loss of <jats:italic>BAP2</jats:italic> and but no other leucine permeases lead to growth retardation in a routine used SCGlu/Gal but not in a SCGlylac medium. Leucine prototrophy suppressed the growth retardation, showing that <jats:italic>BAP2</jats:italic> was synthetically lethal with <jats:italic>LEU2</jats:italic>. We revealed that loss of <jats:italic>BUL1</jats:italic> but not <jats:italic>BUL2</jats:italic> an arrestin involved in trafficking of other diverse permeases suppressed this lethality. The suppression was dependent on another leucine permease <jats:italic>BAP3</jats:italic>. Further experiments revealed that in <jats:italic>bul1Δ</jats:italic> cells, both <jats:italic>BAP2</jats:italic> and <jats:italic>BAP3</jats:italic> accumulated in plasma membrane and their turnover is reduced. Based on our results and what is known, we propose that <jats:italic>BUL1</jats:italic> regulates TORC1 activity by controlling the leucine uptake.</jats:p>