Distinct stages in the recognition, sorting, and packaging of proTGFα into COPII-coated transport vesicles.
In addition to its role in forming vesicles from the endoplasmic reticulum (ER), the coat protein complex II (COPII) is also responsible for selecting specific cargo proteins to be packaged into COPII transport vesicles. Comparison of COPII vesicle formation in mammalian systems and in yeast suggested that the former uses more elaborate mechanisms for cargo recognition, presumably to cope with a significantly expanded repertoire of cargo that transits the secretory pathway. Using proTGFα, the transmembrane precursor of transforming growth factor α (TGFα), as a model cargo protein, we demonstrate in cell-free assays that at least one auxiliary cytosolic factor is specifically required for the efficient packaging of proTGFα into COPII vesicles. Using a knockout HeLa cell line generated by CRISPR/Cas9, we provide functional evidence showing that a transmembrane protein, Cornichon-1 (CNIH), acts as a cargo receptor of proTGFα. We show that both CNIH and the auxiliary cytosolic factor(s) are required for efficient recruitment of proTGFα to the COPII coat in vitro. Moreover, we provide evidence that the recruitment of cargo protein by the COPII coat precedes and may be distinct from subsequent cargo packaging into COPII vesicles.
Department of Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720.
Pengcheng
P
Zhang
Department of Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720 schekman@berkeley.edu.
Randy
R
Schekman
D000818:Animals; D001692:Biological Transport; D022181:COP-Coated Vesicles / Q000378:metabolism* / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D021381:Protein Transport; D016211:Transforming Growth Factor alpha / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism* / Q000502:physiology; D033921:Vesicular Transport Proteins / Q000378:metabolism
D002352:Carrier Proteins; D008565:Membrane Proteins; D011498:Protein Precursors; D016211:Transforming Growth Factor alpha; D033921:Vesicular Transport Proteins; C052268:protransforming growth factor alpha