title: Erv26p-dependent export of alkaline phosphatase from the ER requires lumenal domain recognition.
abstract: Active sorting at the endoplasmic reticulum (ER) drives efficient export of fully folded secretory proteins into coat protein complex II (COPII) vesicles, whereas ER-resident and misfolded proteins are retained and/or degraded. A number of secretory proteins depend upon polytopic cargo receptors for linkage to the COPII coat and ER export. However, the mechanism by which cargo receptors recognize transport-competent cargo is poorly understood. Here we examine the sorting determinants required for export of yeast alkaline phosphatase (ALP) by its cargo receptor Erv26p. Analyses of ALP chimeras and mutants indicated that Erv26p recognizes sorting information in the lumenal domain of ALP. This lumenal domain sorting signal must be positioned near the inner leaflet of the ER membrane for Erv26p-dependent export. Moreover, only assembled ALP dimers were efficiently recognized by Erv26p while an ALP mutant blocked in dimer assembly failed to exit the ER and was subjected to ER-associated degradation. These results further refine sorting information for ER export of ALP and show that recognition of folded cargo by export receptors contributes to strict ER quality control.
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Dancourt
authors.forename: Charles
authors.initials: C
authors.lastname: Barlowe
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D019281:Dimerization; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008364:Mannosyltransferases / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D017510:Protein Folding; D021382:Protein Sorting Signals; D020836:Protein Structure, Quaternary; D021381:Protein Transport / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D000069816:SEC Translocation Channels; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; C075636:OCH1 protein, S cerevisiae; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; C503875:SVP26 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D008364:Mannosyltransferases; D000469:Alkaline Phosphatase