Oligomerization of the yeast alpha-factor receptor: implications for dominant negative effects of mutant receptors.
Oligomerization of G protein-coupled receptors is commonly observed, but the functional significance of oligomerization for this diverse family of receptors remains poorly understood. We used bioluminescence resonance energy transfer (BRET) to examine oligomerization of Ste2p, a G protein-coupled receptor that serves as the receptor for the alpha-mating pheromone in the yeast Saccharomyces cerevisiae, under conditions where the functional effects of oligomerization could be examined. Consistent with previous results from fluorescence resonance energy transfer (Overton, M. C., and Blumer, K. J. (2000) Curr. Biol. 10, 341-344), we detected efficient energy transfer between Renilla luciferase and a modified green fluorescent protein individually fused to truncated alpha-factor receptors lacking the cytoplasmic C-terminal tail. In addition, the low background of the BRET system allowed detection of significant, but less efficient, energy transfer between full-length receptors. The reduced efficiency of energy transfer between full-length receptors does not appear to result from different levels of receptor expression. Instead, attachment of fluorescent reporter proteins to the full-length receptors appears to significantly increase the distance between reporters. Mutations that were previously reported to block dimerization of truncated alpha-factor receptors reduce but do not completely eliminate BRET transfer between receptors. Dominant negative effects of mutant alleles of alpha-factor receptors appear to be mediated by receptor oligomerization since these effects are abrogated by introduction of additional mutations that reduce oligomerization. We find that heterodimers of normal and dominant negative receptors are defective in their ability to signal. Thus, signal transduction by oligomeric receptors appears to be a cooperative process requiring an interaction between functional monomers.
Gehret
Austin U
AU
Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642.
Bajaj
Anshika
A
Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642.
Naider
Fred
F
Department of Chemistry, College of Staten Island, City University of New York, New York, New York 10314.
Dumont
Mark E
ME
Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642. Electronic address: mark_dumont@urmc.rochester.edu.
D019281:Dimerization; D031541:Fluorescence Resonance Energy Transfer; D015966:Gene Expression Regulation, Fungal; D005799:Genes, Dominant; D008156:Luciferases / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry; D051964:Receptors, Mating Factor / Q000737:chemistry* / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics; D015398:Signal Transduction
D043562:Receptors, G-Protein-Coupled; D051964:Receptors, Mating Factor; C498031:STE2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D008156:Luciferases