G Protein Regulation of a Microtubule Motor Protein in Yeast

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

Cellular polarization is essential to morphogenesis, immune response, neuronal development, chemotropism, and motility. Saccharomyces cerevisiae is a well-studied model eukaryote that exhibits numerous polarization phenomena, including signal-induced changes in cell shape and nuclear position. During the haploid phase of their life cycle, yeast cells secrete peptide pheromones that transform vegetatively growing cells of opposite mating type into gametes. Preparatory to cellular and nuclear fusion, pheromone triggers polarized growth toward the mating partner (chemotropism), and migration of the nucleus to the tip of the mating projection. Recent results implicate the pheromone-responsive G-alpha protein, Gpa1, in the control of signal-induced polarized growth and nuclear movement. In cells responding to pheromone, Gpa1 interacts directly with the mating-specific MAPK protein, Fus3, and with Kar3, a microtubule motor protein that is essential for nuclear movement during mating. Disruption of the Gpa1-Fus3 interaction confers defects in chemotropism, microtubule orientation, and nuclear migration. The long-term goal of this project is to understand how G alpha proteins regulate the microtubule cytoskeleton in response to external signals. To this end, genetic, biochemical, mass spectrometric, and imaging approaches will be used to determine how Gpa1 affects the mating-specific functions of Kar3, and whether Fus3 is involved in this regulation. Because Gpa1 and Kar3 provide the first example of a G alpha protein/motor-protein interaction, and because G alpha regulation of nuclear movement is unprecedented, this analysis promises to be informative. This project will also provide significant training opportunity. A graduate student and a postdoctoral fellow will be working on several aspects of the research. In addition, a high school student will be recruited to participate in the project each summer.