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Polarization of the Yeast Pheromone Receptor Requires Its Internalization but Not Actin-dependent Secretion

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posted on 07.05.2011, 00:00 by Dmitry V. Suchkov, Reagan DeFlorio, Edward Draper, Amber Ismael, Madhushalini Sukumar, Robert Arkowitz, David E. Stone
In the best understood models of eukaryotic directional sensing, chemotactic cells maintain a uniform distribution of surface receptors even when responding to chemical gradients. The yeast pheromone receptor is also uniformly distributed on the plasma membrane of vegetative cells, but pheromone induces its polarization into “crescents” that cap the future mating projection. Here, we find that in pheromone-treated cells, receptor crescents are visible before detectable polarization of actin cables and that the receptor can polarize in the absence of actin-dependent directed secretion. Receptor internalization, in contrast, seems to be essential for the generation of receptor polarity, and mutations that deregulate this process confer dramatic defects in directional sensing. We also show that pheromone induces the internalization and subsequent polarization of the mating-specific Gα and Gβ proteins and that the changes in G protein localization depend on receptor internalization and receptor–Gα coupling. Our data suggest that the polarization of the receptor and its G protein precedes actin polarization and is important for gradient sensing. We propose that the establishment of receptor/G protein polarity depends on a novel mechanism involving differential internalization and that this serves to amplify the shallow gradient of activated receptor across the cell.


This work was supported by National Science Foundation grant MCB-0453964 (to D.E.S.) and the American Heart Association grant G7192 (to D.E.S.). R. D. was supported in part by a European Molecular Biology Organization short-term fellowship (ASTF 196-2009) and work in R. A.'s laboratory was supported by the Centre National de la Recherche Scientifique and Fondation pour la Recherche Médicale-BNP-Paribas.


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The original source for this publication is at American Society for Cell Biology; DOI: 10.1091/mbc.E09-08-0706


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