open access

https://hdl.handle.net/2115/51041

Membrane Protein Rim21 Plays a Central Role in Sensing Ambient pH in Saccharomyces cerevisiae

英語

pH Sensing

2012-11-09

American Society for Biochemistry and Molecular Biology

Journal of Biological Chemistry

287(46)

38473-38481

External alkalization activates the Rim101 pathway in Saccharomyces cerevisiae. In this pathway, three integral membrane proteins Rim21, Dfg16, and Rim9 are considered to be the components of the pH-sensor machinery. However, how these proteins are involved in pH sensing is totally unknown. In this work, we investigated the localization, physical interaction, and interrelationship of Rim21, Dfg16, and Rim9. These proteins were found to form a complex and to localize to the plasma membrane in a patchy and mutually-dependent manner. Their cellular level was also mutually dependent. In particular, the Rim21 level was significantly decreased in dfg16Δ and rim9Δ cells. Upon external alkalization, the proteins were internalized and degraded. We also demonstrate that the transient degradation of Rim21 completely suppressed the Rim101 pathway but the degradation of neither Dfg16 nor Rim9 did. This finding strongly suggests that Rim21 is the pH-sensor protein and that Dfg16 and Rim9 play auxiliary functions through maintaining the Rim21 level and assisting its plasma membrane localization. Even without external alkalization, the Rim101 pathway was activated in a Rim21-dependent manner by either protonophore treatment or depletion of phosphatidylserine in the inner leaflet of the plasma membrane, both of which caused plasma membrane depolarization like the external alkalization. Therefore, the plasma membrane depolarization seems to be one of the key signals for the pH-sensor molecule Rim21.

学術雑誌論文

Accepted Manuscript

This research was originally published in Journal of Biological Chemistry. Keisuke Obara, Hayashi Yamamoto and Akio Kihara. Membrane Protein Rim21 Plays a Central Role in Sensing Ambient pH in Saccharomyces cerevisiae. Journal of Biological Chemistry. 2012; 287:38473-38481. © the American Society for Biochemistry and Molecular Biology.

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