The 5' Terminal Oligopyrimidine Tract Confers Translational Control on Top Mrnas in a Cell Type-and Sequence Context-Dependent Manner

Dysfunctional autophagy or ubiquitin-proteasome system (UPS) are suggested to underlie abnormal protein aggregation in neurodegenerative diseases. Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS)-associated C9orf72 is implicated in autophagy, but whether it activates or inhibits autophagy is partially controversial. Here, we utilized knockdown or overexpression of C9orf72 in mouse N2a neuroblastoma cells or cultured neurons to elucidate the potential role of C9orf72 proteins in autophagy and UPS. Induction of autophagy in C9orf72 knockdown N2a cells led to decreased LC3BI to LC3BII conversion, p62 degradation, and formation of LC3-containing autophagosomes, suggesting compromised autophagy. Proteasomal activity was slightly decreased. No changes in autophagy nor proteasomal activity in C9orf72-overexpressing N2a cells were observed. However, in these cells, autophagy induction by serum starvation or rapamycin led to significantly decreased C9orf72 levels. The decreased levels of C9orf72 in serum-starved N2a cells were restored by the proteasomal inhibitor lactacystin, but not by the autophagy inhibitor bafilomycin A1 (BafA1) treatment. These data suggest that C9orf72 undergoes proteasomal degradation in N2a cells during autophagy. Lactacystin significantly elevated C9orf72 levels in N2a cells and neurons, further suggesting UPS-mediated regulation. In rapamycin and BafA1-treated neurons, C9orf72 levels were significantly increased. Altogether, these findings corroborate the previously suggested regulatory role for C9orf72 in autophagy and suggest cell type-dependent regulation of C9orf72 levels via UPS and/or autophagy.

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The Anticoagulant Nafamostat Potently Inhibits SARS-CoV-2 S Protein-Mediated Fusion in a Cell Fusion Assay System and Viral Infection In Vitro in a Cell-Type-Dependent Manner

Viruses ◽

10.3390/v12060629 ◽

2020 ◽

Vol 12 (6) ◽

pp. 629 ◽

Cited By ~ 36

Author(s):

Mizuki Yamamoto ◽

Maki Kiso ◽

Yuko Sakai-Tagawa ◽

Kiyoko Iwatsuki-Horimoto ◽

Masaki Imai ◽

...

Keyword(s):

Cell Fusion ◽

Assay System ◽

Dependent Manner ◽

Cell Type ◽

S Protein ◽

Candidate Drug ◽

A Cell ◽

Transmembrane Serine Protease ◽

Nafamostat Mesylate

Although infection by SARS-CoV-2, the causative agent of coronavirus pneumonia disease (COVID-19), is spreading rapidly worldwide, no drug has been shown to be sufficiently effective for treating COVID-19. We previously found that nafamostat mesylate, an existing drug used for disseminated intravascular coagulation (DIC), effectively blocked Middle East respiratory syndrome coronavirus (MERS-CoV) S protein-mediated cell fusion by targeting transmembrane serine protease 2 (TMPRSS2), and inhibited MERS-CoV infection of human lung epithelium-derived Calu-3 cells. Here we established a quantitative fusion assay dependent on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) S protein, angiotensin I converting enzyme 2 (ACE2) and TMPRSS2, and found that nafamostat mesylate potently inhibited the fusion while camostat mesylate was about 10-fold less active. Furthermore, nafamostat mesylate blocked SARS-CoV-2 infection of Calu-3 cells with an effective concentration (EC)50 around 10 nM, which is below its average blood concentration after intravenous administration through continuous infusion. On the other hand, a significantly higher dose (EC50 around 30 μM) was required for VeroE6/TMPRSS2 cells, where the TMPRSS2-independent but cathepsin-dependent endosomal infection pathway likely predominates. Together, our study shows that nafamostat mesylate potently inhibits SARS-CoV-2 S protein-mediated fusion in a cell fusion assay system and also inhibits SARS-CoV-2 infection in vitro in a cell-type-dependent manner. These findings, together with accumulated clinical data regarding nafamostat’s safety, make it a likely candidate drug to treat COVID-19.

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Either ZEB1 or ZEB2/SIP1 Can Play a Central Role in Regulating the Epstein-Barr Virus Latent-Lytic Switch in a Cell-Type-Specific Manner

Journal of Virology ◽

10.1128/jvi.02706-09 ◽

2010 ◽

Vol 84 (12) ◽

pp. 6139-6152 ◽

Cited By ~ 47

Author(s):

Amy L. Ellis ◽

Zhenxun Wang ◽

Xianming Yu ◽

Janet E. Mertz

Keyword(s):

Cell Lines ◽

Epstein Barr Virus ◽

Cellular Protein ◽

Lytic Replication ◽

Viral Reactivation ◽

Dependent Manner ◽

Cell Type ◽

Barr Virus ◽

A Cell ◽

Epstein Barr

ABSTRACT We previously reported that the cellular protein ZEB1 can repress expression of the Epstein-Barr virus (EBV) BZLF1 gene in transient transfection assays by directly binding its promoter, Zp. We also reported that EBV containing a 2-bp substitution mutation in the ZEB-binding ZV element of Zp spontaneously reactivated out of latency into lytic replication at a higher frequency than did wild-type EBV. Here, using small interfering RNA (siRNA) and short hairpin RNA (shRNA) technologies, we definitively show that ZEB1 is, indeed, a key player in maintaining EBV latency in some epithelial and B-lymphocytic cell lines. However, in other EBV-positive epithelial and B-cell lines, another zinc finger E-box-binding protein, ZEB2/SIP1, is the key player. Both ZEB1 and ZEB2 can bind Zp via the ZV element. In EBV-positive cells containing only ZEB1, knockdown of ZEB1 led to viral reactivation out of latency, with synthesis of EBV immediate-early and early lytic gene products. However, in EBV-positive cells containing both ZEBs, ZEB2, not ZEB1, was the primary ZEB family member bound to Zp. Knockdown of ZEB2, but not ZEB1, led to EBV lytic reactivation. Thus, we conclude that either ZEB1 or ZEB2 can play a central role in the maintenance of EBV latency, doing so in a cell-type-dependent manner.

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The long cytoplasmic tail of gp41 is required in a cell type-dependent manner for HIV-1 envelope glycoprotein incorporation into virions

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.97.1.343 ◽

2000 ◽

Vol 97 (1) ◽

pp. 343-348 ◽

Cited By ~ 182

Author(s):

T. Murakami ◽

E. O. Freed

Keyword(s):

Envelope Glycoprotein ◽

Cytoplasmic Tail ◽

Dependent Manner ◽

Cell Type ◽

A Cell ◽

Hiv 1

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Multiple roles of COUP-TFII in cancer initiation and progression

Journal of Molecular Endocrinology ◽

10.1530/jme-12-0144 ◽

2012 ◽

Vol 49 (3) ◽

pp. R135-R148 ◽

Cited By ~ 28

Author(s):

Lacey M Litchfield ◽

Carolyn M Klinge

Keyword(s):

Current Data ◽

Multiple Roles ◽

Dependent Manner ◽

Orphan Nuclear Receptor ◽

Cell Type ◽

Mouse Development ◽

Factor Ii ◽

Upstream Promoter ◽

A Cell ◽

Cell Type Specific

Chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) is an orphan nuclear receptor that acts as a transcriptional activator or repressor in a cell type-dependent manner. Best characterized for its role in the regulation of angiogenesis during mouse development, COUP-TFII also plays important roles in glucose metabolism and cancer. Expression of COUP-TFII is altered in various endocrine conditions. Cell type-specific functions and the regulation of COUP-TFII expression result in its varying physiological and pathological actions in diverse systems. Evidence will be reviewed for oncogenic and tumor-suppressive functions of COUP-TFII, with roles in angiogenesis, metastasis, steroidogenesis, and endocrine sensitivity of breast cancer described. The applicability of current data to our understanding of the role of COUP-TFII in cancer will be discussed.

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Cell type-specific control of protein synthesis and proliferation by FGF-dependent signaling to the translation repressor 4E-BP

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1605451113 ◽

2016 ◽

Vol 113 (27) ◽

pp. 7545-7550 ◽

Cited By ~ 5

Author(s):

Rachel Ruoff ◽

Olga Katsara ◽

Victoria Kolupaeva

Keyword(s):

Protein Synthesis ◽

Translational Control ◽

Bone Development ◽

Binding Protein ◽

Initiation Factor ◽

Start Codon ◽

Dependent Manner ◽

Fgf Signaling ◽

Cell Type

Regulation of protein synthesis plays a vital role in posttranscriptional modulation of gene expression. Translational control most commonly targets the initiation of protein synthesis: loading 40S ribosome complexes onto mRNA and AUG start codon recognition. This step is initiated by eukaryotic initiation factor 4E (eIF4E) (the m7GTP cap-binding protein), whose binding to eIF4G (a scaffolding subunit) and eIF4A (an ATP-dependent RNA helicase) leads to assembly of active eIF4F complex. The ability of eIF4E to recognize the cap is prevented by its binding to eIF4E binding protein (4E-BP), which thereby inhibits cap-dependent translation by sequestering eIF4E. The 4E-BP activity is, in turn, inhibited by mTORC1 [mTOR (the mechanistic target of rapamycin) complex 1] mediated phosphorylation. Here, we define a previously unidentified mechanism of mTOR-independent 4E-BP1 regulation that is used by chondrocytes upon FGF signaling. Chondrocytes are responsible for the formation of the skeleton long bones. Unlike the majority of cell types where FGF signaling triggers proliferation, chondrocytes respond to FGF with inhibition. We establish that FGF specifically suppresses protein synthesis in chondrocytes, but not in any other cells of mesenchymal origin. Furthermore, 4E-BP1 repressor activity is necessary not only for suppression of protein synthesis, but also for FGF-induced cell-cycle arrest. Importantly, FGF-induced changes in the 4E-BP1 activity observed in cell culture are likewise detected in vivo and reflect the action of FGF signaling on downstream targets during bone development. Thus, our findings demonstrate that FGF signaling differentially impacts protein synthesis through either stimulation or repression, in a cell-type–dependent manner, with 4E-BP1 being a key player.

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