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Mol Biol Cell

Title:		Specific sterols required for the internalization step of endocytosis in yeast
Author(s):		Munn AL; Heese-Peck A; Stevenson BJ; Pichler H; Riezman H;
Address:		"Biozentrum of the University of Basel, CH-4056 Basel, Switzerland"
Journal Title:		Mol Biol Cell
Year:		1999
Volume:		10
Issue:		11
Page Number:		3943 - 3957
DOI:		10.1091/mbc.10.11.3943
ISSN/ISBN:		1059-1524 (Print) 1059-1524 (Linking)
Abstract:		"Sterols are major components of the plasma membrane, but their functions in this membrane are not well understood. We isolated a mutant defective in the internalization step of endocytosis in a gene (ERG2) encoding a C-8 sterol isomerase that acts in the late part of the ergosterol biosynthetic pathway. In the absence of Erg2p, yeast cells accumulate sterols structurally different from ergosterol, which is the major sterol in wild-type yeast. To investigate the structural requirements of ergosterol for endocytosis in more detail, several erg mutants (erg2Delta, erg6Delta, and erg2Deltaerg6Delta) were made. Analysis of fluid phase and receptor-mediated endocytosis indicates that changes in the sterol composition lead to a defect in the internalization step. Vesicle formation and fusion along the secretory pathway were not strongly affected in the ergDelta mutants. The severity of the endocytic defect correlates with changes in sterol structure and with the abundance of specific sterols in the ergDelta mutants. Desaturation of the B ring of the sterol molecules is important for the internalization step. A single desaturation at C-8,9 was not sufficient to support internalization at 37 degrees C whereas two double bonds, either at C-5,6 and C-7,8 or at C-5,6 and C-8,9, allowed internalization"
Keywords:		"Carboxypeptidases/metabolism Cathepsin A Cloning, Molecular Endocytosis/*genetics Ergosterol/biosynthesis Glycoside Hydrolases/metabolism Kinetics Mating Factor Microscopy, Phase-Contrast Molecular Structure Mutation Peptides/metabolism Steroid Isomerases;"
Notes:		"MedlineMunn, A L Heese-Peck, A Stevenson, B J Pichler, H Riezman, H eng Research Support, Non-U.S. Gov't 1999/11/17 Mol Biol Cell. 1999 Nov; 10(11):3943-57. doi: 10.1091/mbc.10.11.3943"