title: The cytoplasmic tail of the severe acute respiratory syndrome coronavirus spike protein contains a novel endoplasmic reticulum retrieval signal that binds COPI and promotes interaction with membrane protein.
abstract: Like other coronaviruses, severe acute respiratory syndrome coronavirus (SARS CoV) assembles at and buds into the lumen of the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC). Accumulation of the viral envelope proteins at this compartment is a prerequisite for virus assembly. Previously, we reported the identification of a dibasic motif (KxHxx) in the cytoplasmic tail of the SARS CoV spike (S) protein that was similar to a canonical dilysine ER retrieval signal. Here we demonstrate that this motif is a novel and functional ER retrieval signal which reduced the rate of traffic of the full-length S protein through the Golgi complex. The KxHxx motif also partially retained two different reporter proteins in the ERGIC region and reduced their rates of trafficking, although the motif was less potent than the canonical dilysine signal. The dibasic motif bound the coatomer complex I (COPI) in an in vitro binding assay, suggesting that ER retrieval may contribute to the accumulation of SARS CoV S protein near the virus assembly site for interaction with other viral structural proteins. In support of this, we found that the dibasic motif on the SARS S protein was required for its localization to the ERGIC/Golgi region when coexpressed with SARS membrane (M) protein. Thus, the cycling of SARS S through the ER-Golgi system may be required for its incorporation into assembling virions in the ERGIC.
authors.affiliation: Department of Cell Biology, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA.
authors.forename: Corrin E
authors.initials: CE
authors.lastname: McBride
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Carolyn E
authors.initials: CE
authors.lastname: Machamer
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology; D020755:Coat Protein Complex I / Q000378:metabolism*; D000086862:Coronavirus M Proteins; D003593:Cytoplasm / Q000821:virology; D004721:Endoplasmic Reticulum / Q000821:virology; D006056:Golgi Apparatus / Q000821:virology; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D020755:Coat Protein Complex I; D000086862:Coronavirus M Proteins; C000706237:M protein, SARS-CoV; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; D014763:Viral Matrix Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus