scholarly journals A novel RCE1 isoform is required for H-Ras plasma membrane localization and is regulated by USP17

2013 ◽  
Vol 457 (2) ◽  
pp. 289-300 ◽  
Author(s):  
Jakub Jaworski ◽  
Ureshnie Govender ◽  
Cheryl McFarlane ◽  
Michelle de la Vega ◽  
Michelle K. Greene ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Localization ◽  
Plasma Membrane Localization

We have identified a novel RCE1 isoform which is required for proper H-Ras processing and plasma membrane localization. In addition, we have shown that USP17 can regulate this novel isoform and thus RCE1 activity by deubiquitinating Lys43.

scholarly journals Lipid binding by the N-terminal motif mediates plasma membrane localization of Bordetella effector protein BteA

2021 ◽  
pp. 100607
Author(s):  
Ivana Malcova ◽  
Ladislav Bumba ◽  
Filip Uljanic ◽  
Darya Kuzmenko ◽  
Jana Nedomova ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Lipid Binding ◽  
Membrane Localization ◽  
Effector Protein ◽  
Plasma Membrane Localization

scholarly journals Palmitoylation of Sindbis Virus TF Protein Regulates Its Plasma Membrane Localization and Subsequent Incorporation into Virions

2016 ◽  
Vol 91 (3) ◽  
Author(s):  
Jolene Ramsey ◽  
Emily C. Renzi ◽  
Randy J. Arnold ◽  
Jonathan C. Trinidad ◽  
Suchetana Mukhopadhyay
Keyword(s):  
Plasma Membrane ◽  
Sindbis Virus ◽  
Molecular Mechanisms ◽  
Wild Type Virus ◽  
Membrane Localization ◽  
Clear Understanding ◽  
Wild Type ◽  
Plasma Membrane Localization ◽  
C Terminus ◽  
N Terminus

ABSTRACT Palmitoylation is a reversible, posttranslational modification that helps target proteins to cellular membranes. The alphavirus small membrane proteins 6K and TF have been reported to be palmitoylated and to positively regulate budding. 6K and TF are isoforms that are identical in their N termini but unique in their C termini due to a −1 ribosomal frameshift during translation. In this study, we used cysteine (Cys) mutants to test differential palmitoylation of the Sindbis virus 6K and TF proteins. We modularly mutated the five Cys residues in the identical N termini of 6K and TF, the four additional Cys residues in TF's unique C terminus, or all nine Cys residues in TF. Using these mutants, we determined that TF palmitoylation occurs primarily in the N terminus. In contrast, 6K is not palmitoylated, even on these shared residues. In the C-terminal Cys mutant, TF protein levels increase both in the cell and in the released virion compared to the wild type. In viruses with the N-terminal Cys residues mutated, TF is much less efficiently localized to the plasma membrane, and it is not incorporated into the virion. The three Cys mutants have minor defects in cell culture growth but a high incidence of abnormal particle morphologies compared to the wild-type virus as determined by transmission electron microscopy. We propose a model where the C terminus of TF modulates the palmitoylation of TF at the N terminus, and palmitoylated TF is preferentially trafficked to the plasma membrane for virus budding. IMPORTANCE Alphaviruses are a reemerging viral cause of arthritogenic disease. Recently, the small 6K and TF proteins of alphaviruses were shown to contribute to virulence in vivo. Nevertheless, a clear understanding of the molecular mechanisms by which either protein acts to promote virus infection is missing. The TF protein is a component of budded virions, and optimal levels of TF correlate positively with wild-type-like particle morphology. In this study, we show that the palmitoylation of TF regulates its localization to the plasma membrane, which is the site of alphavirus budding. Mutants in which TF is not palmitoylated display drastically reduced plasma membrane localization, which effectively prevents TF from participating in budding or being incorporated into virus particles. Investigation of the regulation of TF will aid current efforts in the alphavirus field searching for approaches to mitigate alphaviral disease in humans.

scholarly journals Role of Ezrin/Radixin/Moesin in the Surface Localization of Programmed Cell Death Ligand-1 in Human Colon Adenocarcinoma LS180 Cells

2021 ◽  
Vol 14 (9) ◽  
pp. 864
Author(s):  
Takuro Kobori ◽  
Chihiro Tanaka ◽  
Mayuka Tameishi ◽  
Yoko Urashima ◽  
Takuya Ito ◽  
...  
Keyword(s):  
Cell Death ◽  
Plasma Membrane ◽  
Programmed Cell Death ◽  
Cell Surface ◽  
Actin Cytoskeleton ◽  
Mrna Level ◽  
Scaffold Proteins ◽  
Membrane Localization ◽  
Erm Proteins ◽  
Plasma Membrane Localization

Programmed cell death ligand-1 (PD-L1), an immune checkpoint protein highly expressed on the cell surface in various cancer cell types, binds to programmed cell death-1 (PD-1), leading to T-cell dysfunction and tumor survival. Despite clinical successes of PD-1/PD-L1 blockade therapies, patients with colorectal cancer (CRC) receive little benefit because most cases respond poorly. Because high PD-L1 expression is associated with immune evasion and poor prognosis in CRC patients, identifying potential modulators for the plasma membrane localization of PD-L1 may represent a novel therapeutic strategy for enhancing the efficacy of PD-1/PD-L1 blockade therapies. Here, we investigated whether PD-L1 expression in human colorectal adenocarcinoma cells (LS180) is affected by ezrin/radixin/moesin (ERM), functioning as scaffold proteins that crosslink plasma membrane proteins with the actin cytoskeleton. We observed colocalization of PD-L1 with all three ERM proteins in the plasma membrane and detected interactions involving PD-L1, the three ERM proteins, and the actin cytoskeleton. Furthermore, gene silencing of ezrin and radixin, but not of moesin, substantially decreased the expression of PD-L1 on the cell surface without affecting its mRNA level. Thus, in LS180 cells, ezrin and radixin may function as scaffold proteins mediating the plasma membrane localization of PD-L1, possibly by post-translational modification.

scholarly journals Identification of SERINC5-001 as the Predominant Spliced Isoform for HIV-1 Restriction

2017 ◽  
Vol 91 (10) ◽  
Author(s):  
Xianfeng Zhang ◽  
Tao Zhou ◽  
Jie Yang ◽  
Yumei Lin ◽  
Jing Shi ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Transmembrane Domain ◽  
The Other ◽  
Stable Expression ◽  
Membrane Localization ◽  
Plasma Membrane Localization ◽  
Immunodeficiency Virus ◽  
Alternatively Spliced ◽  
Anti Hiv ◽  
Hiv 1

ABSTRACT Among the five serine incorporator (SERINC) family members, SERINC5 (Ser5) was reported to strongly inhibit HIV-1 replication, which is counteracted by Nef. Ser5 produces 5 alternatively spliced isoforms: Ser5-001 has 10 putative transmembrane domains, whereas Ser5-004, -005, -008a, and -008b do not have the last one. Here, we confirmed the strong Ser5 anti-HIV-1 activity and investigated its isoforms' expression and antiviral activities. It was found that Ser5-001 transcripts were detected at least 10-fold more than the other isoforms by real-time quantitative PCR. When Ser5-001 and its two isoforms Ser5-005 and Ser5-008a were expressed from the same mammalian expression vector, only Ser5-001 was stably expressed, whereas the others were poorly expressed due to rapid degradation. In addition, unlike the other isoforms, which are located mainly in the cytoplasm, Ser5-001 is localized primarily to the plasma membrane. To map the critical determinant, Ser5 mutants bearing C-terminal deletions were created. It was found that the 10th transmembrane domain is required for Ser5 stable expression and plasma membrane localization. As expected, only Ser5-001 strongly inhibits HIV-1 infectivity, whereas the other Ser5 isoforms and mutants that do not have the 10th transmembrane domain show very poor activity. It was also observed that the Nef counteractive activity could be easily saturated by Ser5 overexpression. Thus, we conclude that Ser5-001 is the predominant antiviral isoform that restricts HIV-1, and the 10th transmembrane domain plays a critical role in this process by regulating its protein stability and plasma membrane targeting. IMPORTANCE Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) express a small protein, Nef, to enhance viral pathogenesis in vivo. Nef has an important in vitro function, which is to make virus particles more infectious, but the mechanism has been unclear. Recently, Nef was reported to counteract a novel anti-HIV host protein, SERINC5 (Ser5). Ser5 has five alternatively spliced isoforms, Ser5-001, -004, -005, -008a, and -008b, and only Ser5-001 has an extra C-terminal transmembrane domain. We now show that the Ser5-001 transcripts are produced at least 10-fold more than the others, and only Ser5-001 produces stable proteins that are targeted to the plasma membrane. Importantly, only Ser5-001 shows strong anti-HIV-1 activity. We further demonstrate that the extra transmembrane domain is required for Ser5 stable expression and plasma membrane localization. These results suggest that plasma membrane localization is required for Ser5 antiviral activity, and Ser5-001 is the predominant isoform that contributes to the activity.

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