scholarly journals The Cytoplasmic Tail of the Mouse Brown Locus Product Determines Intracellular Stability and Export from the Endoplasmic Reticulum

1998 ◽  
Vol 110 (4) ◽  
pp. 324-331 ◽  
Author(s):  
Yiqing Xu ◽  
Setaluri Vijayasaradhi ◽  
Alan N. Houghton
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytoplasmic Tail ◽  
Locus Product

scholarly journals Deletion of both the Tyrosine-Based Endocytosis Signal and the Endoplasmic Reticulum Retrieval Signal in the Cytoplasmic Tail of Spike Protein Attenuates Porcine Epidemic Diarrhea Virus in Pigs

2018 ◽  
Vol 93 (2) ◽  
Author(s):  
Yixuan Hou ◽  
Tea Meulia ◽  
Xiang Gao ◽  
Linda J. Saif ◽  
Qiuhong Wang
Keyword(s):  
Endoplasmic Reticulum ◽  
Vero Cell ◽  
Porcine Epidemic Diarrhea Virus ◽  
Cytoplasmic Tail ◽  
S Protein ◽  
Diarrhea Virus ◽  
Neonatal Piglets ◽  
Porcine Epidemic Diarrhea ◽  
Intracellular Sorting ◽  
S Proteins

ABSTRACTPorcine epidemic diarrhea virus (PEDV) causes high mortality in neonatal piglets. The PEDV spike (S) protein contains two intracellular sorting motifs, YxxΦ (tyrosine-based motif YEVF or YEAF) and KVHVQ at the cytoplasmic tail, yet their functions have not been fully elucidated. Some Vero cell-adapted and/or attenuated PEDV variants contain ablations in these two motifs. We hypothesized that these motifs contribute to viral pathogenicity. By transiently expressing PEDV S proteins with mutations in the motifs, we confirmed that the motif KVHVQ is involved in retention of the S proteins in the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC). In addition, we showed that the YxxΦ motif triggers endocytosis of S proteins. These two motifs synergistically regulate the level of S expressed on the cell surface. To investigate their role in viral pathogenicity, we generated three recombinant PEDVs by introducing deletions or a mutation in the two motifs of the infectious clone of PEDV PC22A strain (icPC22A): (i) icΔ10aa (ΔYxxΦEKVHVQ), (ii) icΔ5aa (ΔKVHVQ), and (iii) icYA (Y1378A, to an inactivated motif, AEVF). Infection of Vero cells with icΔ10aa resulted in larger syncytia and more virions, with reduced numbers of S protein projections on the surface compared with icPC22A. Furthermore, we orally inoculated five groups of 5-day-old gnotobiotic piglets with the three mutants, icPC22A, or a mock treatment. Mutant icΔ10aa caused less severe diarrhea rate and significantly milder intestinal lesions than icPC22A, icΔ5aa, and icYA. These data suggest that the deletion of both motifs can reduce the virulence of PEDV in piglets.IMPORTANCEMany coronaviruses (CoVs) possess conserved motifs YxxΦ and/or KxHxx/KKxx in the cytoplasmic tail of the S protein. The KxHxx/KKxx motif has been identified as the ER retrieval signal, but the function of the YxxΦ motif in the intracellular sorting of CoV S proteins remains controversial. In this study, we showed that the YxxΦ of PEDV S protein is an endocytosis signal. Furthermore, using reverse genetics technology, we evaluated its role in PEDV pathogenicity in neonatal piglets. Our results explain one attenuation mechanism of Vero cell-adapted PEDV variants lacking functional YxxΦ and KVHVQ motifs. Knowledge from this study may aid in the design of efficacious live attenuated vaccines against PEDV, as well as other CoVs bearing the same motif in their S protein.

scholarly journals Non-muscle myosin IIA transports a Golgi glycosyltransferase to the endoplasmic reticulum by binding to its cytoplasmic tail

2012 ◽  
Vol 44 (7) ◽  
pp. 1153-1165 ◽  
Author(s):  
Armen Petrosyan ◽  
Mohamed F. Ali ◽  
Shailendra Kumar Verma ◽  
Helen Cheng ◽  
Pi-Wan Cheng
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytoplasmic Tail ◽  
Myosin Iia ◽  
Muscle Myosin

scholarly journals Calnexin retains unassembled major histocompatibility complex class I free heavy chains in the endoplasmic reticulum.

1994 ◽  
Vol 180 (1) ◽  
pp. 407-412 ◽  
Author(s):  
S Rajagopalan ◽  
M B Brenner
Keyword(s):  
Endoplasmic Reticulum ◽  
Major Histocompatibility Complex ◽  
Cell Surface ◽  
Mhc Class I ◽  
Cytoplasmic Tail ◽  
Class I ◽  
Major Histocompatibility ◽  
Stable Transfectants ◽  
Histocompatibility Complex ◽  
Er Retention

The assembly of major histocompatibility complex (MHC) class I molecules involves the association of heavy (H) chain with beta 2-microglobulin (beta 2m) and peptide. Unassembled class I H chains do not exit the endoplasmic reticulum (ER) and this is exemplified by the beta 2m-deficient human melanoma FO-1 where free class I H chains are unable to complete assembly. In pulse chase experiments involving FO-1 cells, unassembled free class I H chains were shown to be stably associated with calnexin (IP90/p88), a 90-kD integral membrane molecular chaperone of the ER. To establish a role for calnexin in mediating this retention, we transfected FO-1 cells with a cytoplasmic tail deletion mutant of calnexin. Since the cytoplasmic tail contains the ER retention motif, these mutant calnexin molecules leave the ER and progress to the cell surface. In these stable transfectants of FO-1, free class I H chains also exited the ER and trafficked to the cell surface with calnexin, thus establishing a role for calnexin in the quality control of MHC class I assembly through mediating the ER retention of incompletely assembled class I H chains.

scholarly journals 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

2006 ◽  
Vol 81 (5) ◽  
pp. 2418-2428 ◽  
Author(s):  
Corrin E. McBride ◽  
Jie Li ◽  
Carolyn E. Machamer
Keyword(s):  
Endoplasmic Reticulum ◽  
Severe Acute Respiratory Syndrome ◽  
Virus Assembly ◽  
Cytoplasmic Tail ◽  
Viral Envelope ◽  
S Protein ◽  
Golgi Region ◽  
Vitro Binding ◽  
Intermediate Compartment

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.

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