title: Selective protein exit from yeast endoplasmic reticulum in absence of functional COPII coat component Sec13p.
abstract: Sec13p has been thought to be an essential component of the COPII coat, required for exit of proteins from the yeast endoplasmic reticulum (ER). We show herein that normal function of Sec13p was not required for ER exit of the Hsp150 glycoprotein. Hsp150 was secreted to the medium under restrictive conditions in a sec13-1 mutant. The COPII components Sec23p and Sec31p and the GTP/GDP exchange factor Sec12p were required in functional form for secretion of Hsp150. Hsp150 leaves the ER in the absence of retrograde COPI traffic, and the responsible determinant is a peptide repeated 11 times in the middle of the Hsp150 sequence. Herein, we localized the sorting determinant for Sec13p-independent ER exit to the C-terminal domain. Sec13p-dependent invertase left the ER in the absence of normal Sec13p function, when fused to the C-terminal domain of Hsp150, demonstrating that this domain contained an active mediator of Sec13p-independent secretion. Thus, Hsp150 harbors two different signatures that regulate its ER exit. Our data show that transport vesicles lacking functional Sec13p can carry out ER-to-Golgi transport, but select only specific cargo protein(s) for ER exit.
authors.affiliation: Program in Cellular Biotechnology, Institute of Biotechnology, Viikki Biocenter, 00014 University of Helsinki, Finland.
authors.forename: Netta
authors.initials: N
authors.lastname: Fatal
authors.forename: Taina
authors.initials: T
authors.lastname: Suntio
authors.forename: Marja
authors.initials: M
authors.lastname: Makarow
mesh_terms: D022181:COP-Coated Vesicles / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D005656:Fungal Proteins / Q000737:chemistry* / Q000378:metabolism; D006023:Glycoproteins; D006056:Golgi Apparatus / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D006360:Heat-Shock Proteins / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000502:physiology; D009154:Mutation; D028861:Nuclear Pore Complex Proteins; D010750:Phosphoproteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D013997:Time Factors; D033921:Vesicular Transport Proteins; D015003:Yeasts / Q000378:metabolism; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; D006023:Glycoproteins; D020662:Guanine Nucleotide Exchange Factors; C074229:HSP150 protein, S cerevisiae; D006360:Heat-Shock Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; D010750:Phosphoproteins; C071239:SEC12 protein, S cerevisiae; C079620:SEC13 protein, S cerevisiae; C106113:SEC31 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D001618:beta-Lactamases