Most of plasma membrane transporters are downregulated by ubiquitination-dependent endocytosis to avoid the excess uptake of their substrates. In Saccharomyces cerevisiae, ubiquitination of transporters is mediated by the HECT-type ubiquitin ligase Rsp5. We report here a mechanism underlying the substrate-induced endocytosis of the broad-specificity amino acid permease Agp1. First, we found that Agp1 underwent ubiquitination and endocytosis in response to the addition of excess asparagine, which is a substrate of Agp1. Moreover, the substrate-induced internalization of Agp1 was dependent on the ubiquitination activity of Rsp5. Since Rsp5 requires α-arrestin family proteins as adaptors to bind with substrates, we next developed a method of genetic screening to identify adaptor proteins for Agp1 endocytosis. This screening and biochemical analysis revealed that Bul1, but not its paralogue Bul2, was essential for the substrate-induced endocytosis of Agp1. Our results support that the substrate-induced endocytosis of Agp1 requires Rsp5 and Bul1.
CITATION STYLE
Tanahashi, R., Matsushita, T., Nishimura, A., & Takagi, H. (2021). Downregulation of the broad-specificity amino acid permease Agp1 mediated by the ubiquitin ligase Rsp5 and the arrestin-like protein Bul1 in yeast. Bioscience, Biotechnology and Biochemistry, 85(5), 1266–1274. https://doi.org/10.1093/bbb/zbab028
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