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Eukaryot Cell

Title:		Prm1 targeting to contact sites enhances fusion during mating in Saccharomyces cerevisiae
Author(s):		Olmo VN; Grote E;
Address:		"Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21144, USA"
Journal Title:		Eukaryot Cell
Year:		2010
Volume:		20100820
Issue:		10
Page Number:		1538 - 1548
DOI:		10.1128/EC.00116-10
ISSN/ISBN:		1535-9786 (Electronic) 1535-9778 (Print) 1535-9786 (Linking)
Abstract:		"Prm1 is a pheromone-regulated membrane glycoprotein involved in the plasma membrane fusion event of Saccharomyces cerevisiae mating. Although this function suggests that Prm1 should act at contact sites in pairs of mating yeast cells where plasma membrane fusion occurs, only a small percentage of the total Prm1 was actually detected on the plasma membrane. We therefore investigated the intracellular transport of Prm1 and how this transport contributes to cell fusion. Two Prm1 chimeras that were sorted away from the contact site had reduced fusion activity, indicating that Prm1 indeed functions at contact sites. However, most Prm1 is located in endosomes and other cytoplasmic organelles and is targeted to vacuoles for degradation. Mutations in a putative endocytosis signal in a cytoplasmic loop partially stabilized the Prm1 protein and caused it to accumulate on the plasma membrane, but this endocytosis mutant actually had reduced mating activity. When Prm1 was expressed from a galactose-regulated promoter and its synthesis was repressed at the start of mating, vanishingly small amounts of Prm1 protein remained at the time when the plasma membranes came into contact. Nevertheless, this stable pool of Prm1 was retained at polarized sites on the plasma membrane and was sufficient to promote plasma membrane fusion. Thus, the amount of Prm1 expressed in mating yeast is far in excess of the amount required to facilitate fusion"
Keywords:		Amino Acid Sequence Cell Membrane/*metabolism Cell Polarity Membrane Fusion/*physiology Membrane Proteins/genetics/*metabolism/physiology Molecular Sequence Data Saccharomyces cerevisiae/cytology/genetics/*physiology Saccharomyces cerevisiae Proteins/gene;
Notes:		"MedlineOlmo, Valerie N Grote, Eric eng T32 CA009110/CA/NCI NIH HHS/ 2010/08/24 Eukaryot Cell. 2010 Oct; 9(10):1538-48. doi: 10.1128/EC.00116-10. Epub 2010 Aug 20"