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Mol Cell Biol

Title:		Direct evidence for ligand-induced internalization of the yeast alpha-factor pheromone receptor
Author(s):		Schandel KA; Jenness DD;
Address:		"Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655-0122"
Journal Title:		Mol Cell Biol
Year:		1994
Volume:		14
Issue:		11
Page Number:		7245 - 7255
DOI:		10.1128/mcb.14.11.7245-7255.1994
ISSN/ISBN:		0270-7306 (Print) 1098-5549 (Electronic) 0270-7306 (Linking)
Abstract:		"When Saccharomyces cerevisiae a cells bind alpha-factor pheromone, the ligand is internalized and its binding sites are lost from the cell surface in a time-, energy-, and temperature-dependent manner. This report presents direct evidence for alpha-factor-induced internalization of cell surface receptors. First, membrane fractionation on Renografin density gradients indicated that the alpha-factor receptors were predominantly found in the plasma membrane peak before alpha-factor treatment and then appeared in membranes of lesser buoyant density after alpha-factor exposure. Second, receptors were susceptible to cleavage by extracellular proteases before alpha-factor treatment and then became resistant to proteolysis after exposure to pheromone, consistent with the transit of receptors from the cell surface to an internal compartment. The median transit time in both assays was approximately 8 min. The ultimate target of the internalized receptors was identified as the vacuole, since the membranes containing internalized receptors cofractionated with vacuolar membranes, since the turnover of receptors was stimulated by alpha-factor exposure, and since receptor degradation was blocked in a pep4 mutant that is deficient for vacuolar proteases. The carboxy-terminal domain of the receptor that is required for ligand internalization was also found to be essential for endocytosis of the receptor. A receptor mutant, ste2-L236H, which is defective for pheromone response but capable of ligand internalization, was found to be proficient for receptor endocytosis. Hence, separate structural features of the receptor appear to specify its signal transduction and internalization activities"
Keywords:		"Biological Transport, Active Cell Membrane/metabolism Endocytosis Endopeptidases/metabolism Genes, Fungal Kinetics Mating Factor Mutation Peptides/*metabolism Receptors, Mating Factor Receptors, Peptide/genetics/*metabolism Saccharomyces cerevisiae/geneti;"
Notes:		"MedlineSchandel, K A Jenness, D D eng GM34719/GM/NIGMS NIH HHS/ Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. 1994/11/01 Mol Cell Biol. 1994 Nov; 14(11):7245-55. doi: 10.1128/mcb.14.11.7245-7255.1994"