Synergetic contributions of viral VP1, VP3, and 3C to activation of the AKT-AMPK-MAPK-MTOR signaling pathway for Seneca Valley virus-induced autophagy

2021 ◽  
Author(s):  
Jiangwei Song ◽  
Lei Hou ◽  
Rong Quan ◽  
Dan Wang ◽  
Haijun Jiang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Viral Replication ◽  
Signaling Pathway ◽  
P38 Mapk ◽  
Mtor Pathway ◽  
Mtor Signaling Pathway ◽  
Unfolded Protein ◽  
Autophagy Induction ◽  
Seneca Valley Virus ◽  
Protein Response

Seneca Valley virus (SVV), a member of the Picornaviridae family, can activate autophagy via the PERK and ATF6 unfolded protein response pathways and facilitate viral replication; however, the precise molecular mechanism that regulates SVV-induced autophagy remains unclear. Here, we revealed that SVV infection inhibited the phosphorylation of mechanistic target of rapamycin kinase (MTOR) and activated phosphorylation of the serine/threonine kinase AKT. We observed that activating adenosine monophosphate-activated protein kinase (AMPK), extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK), and p38 MAPK signaling by SVV infection promoted autophagy induction and viral replication; additionally, the SVV-induced autophagy was independent of the ULK1 complex. We further evaluated the role of viral protein(s) in the AKT-AMPK-MAPK-MTOR pathway during SVV-induced autophagy and found that VP1 induced autophagy, as evidenced by puncta colocalization with microtubule-associated protein 1 light chain 3 (LC3) in the cytoplasm and enhanced LC3-II levels. This might be associated with the interaction of VP1 with sequestosome 1 and promoting its degradation. In addition, the expression of VP1 enhanced AKT phosphorylation and AMPK phosphorylation, while MTOR phosphorylation was inhibited. These results indicate that VP1 induces autophagy by the AKT-AMPK-MTOR pathway. Additionally, expression of VP3 and 3C was found to activate autophagy induction via the ERK1/2 MAPK-MTOR and p38 MAPK-MTOR pathway. Taken together, our data suggest that SVV-induced autophagy has finely-tuned molecular mechanisms in which VP1, VP3, and 3C contribute synergistically to the AKT-AMPK-MAPK-MTOR pathway. IMPORTANCE Autophagy is an essential cellular catabolic process to sustain normal physiological processes that modulated by a variety of signaling pathways. Invading virus is a stimulus to induce autophagy that regulates viral replication. It has been demonstrated that Seneca Valley virus (SVV) induced autophagy via the PERK and ATF6 unfolded protein response pathways. However, the precise signaling pathway involved in autophagy is still poorly understood. In this study, our results demonstrated that viral proteins VP1, VP3, and 3C contribute synergistically to activation of the AKT-AMPK-MAPK-MTOR signaling pathway for SVV-induced autophagy. These findings reveal systemically the finely-tuned mocleular mechanism of SVV-induced autophagy, thereby facilitating to deeper insight into the development of potential control strategies against SVV infection.

scholarly journals sMEK1 promotes crosstalk between IRE1 and Akt signaling pathway: Evidence for a novel IRE1/sMEK1/Akt complex

2021 ◽  
Author(s):  
ozaira qadri ◽  
Samirul Bashir ◽  
Mariam Banday ◽  
Nazia Hilal ◽  
Khalid M Fazili
Keyword(s):  
Protein Kinase ◽  
Er Stress ◽  
Signaling Pathway ◽  
Molecular Mechanism ◽  
Ternary Complex ◽  
Akt Signaling ◽  
Akt Signaling Pathway ◽  
Unfolded Protein ◽  
Central Molecule ◽  
Protein Response

ER is facilitated with a dynamic cellular pathway namely Unfolded Protein Response (UPR): an adaptive signalling mechanism that maintains proteostasis in response to ER stress. IRE1 is one of the three transmembrane sensors of UPR with dual protein kinase and ribonuclease activities. IRE1 acts as a central molecule of UPR, which associates with a number of proteins that either regulate its activity or connect it to other pathways. Here, we report sMEK1 and Akt as novel interacting partners of IRE1 which associate to orchestrate the IRE1 and Akt signalling networks. Our study revealed that ER stress negatively regulates Akt through IRE1 protein. We found that IRE1/sMEK1/Akt form a ternary complex, which results in the dephosphorylation of Akt by protein phosphotase sMEK1 in presence of activated IRE1. Together, this study highlights the UPR/Akt link by delineating the molecular mechanism along with giving insights into the overall impact of this interaction.

scholarly journals Porcine Reproductive and Respiratory Syndrome Virus Infection Induces both eIF2α Phosphorylation-Dependent and -Independent Host Translation Shutoff

2018 ◽  
Vol 92 (16) ◽  
Author(s):  
Yang Li ◽  
Liurong Fang ◽  
Yanrong Zhou ◽  
Ran Tao ◽  
Dang Wang ◽  
...  
Keyword(s):  
Viral Replication ◽  
Signaling Pathway ◽  
Mtor Pathway ◽  
Mtor Signaling ◽  
Initiation Factor ◽  
Respiratory Syndrome Virus ◽  
Eukaryotic Initiation Factor ◽  
Mtor Signaling Pathway ◽  
Eif2α Phosphorylation ◽  
Tm Domain

ABSTRACTPorcine reproductive and respiratory syndrome virus (PRRSV) is anArterivirusthat has caused tremendous economic losses in the global swine industry since it was discovered in the late 1980s. Inducing host translation shutoff is a strategy used by many viruses to optimize their replication and spread. Here, we demonstrate that PRRSV infection causes host translation suppression, which is strongly dependent on viral replication. By screening PRRSV-encoded nonstructural proteins (nsps), we found that nsp2 participates in the induction of host translation shutoff and that its transmembrane (TM) domain is required for this process. nsp2-induced translation suppression is independent of protein degradation pathways and the phosphorylation of eukaryotic initiation factor 2α (eIF2α). However, the overexpression of nsp2 or its TM domain significantly attenuated the mammalian target of rapamycin (mTOR) signaling pathway, an alternative pathway for modulating host gene expression. PRRSV infection also attenuated the mTOR signaling pathway, and PRRSV-induced host translation shutoff could be partly reversed when the attenuated mTOR phosphorylation was reactivated by an activator of the mTOR pathway. PRRSV infection still negatively regulated the host translation when the effects of eIF2α phosphorylation were completely reversed. Taken together, our results demonstrate that PRRSV infection induces host translation shutoff and that nsp2 is associated with this process. Both eIF2α phosphorylation and the attenuation of the mTOR signaling pathway contribute to PRRSV-induced host translation arrest.IMPORTANCEViruses are obligate parasites, and the production of progeny viruses relies strictly on the host translation machinery. Therefore, the efficient modulation of host mRNA translation benefits viral replication, spread, and evolution. In this study, we provide evidence that porcine reproductive and respiratory syndrome virus (PRRSV) infection induces host translation shutoff and that the viral nonstructural protein nsp2 is associated with this process. Many viruses induce host translation shutoff by phosphorylating eukaryotic initiation factor 2α (eIF2α). However, PRRSV nsp2 does not induce eIF2α phosphorylation but attenuates the mTOR signaling pathway, another pathway regulating the host cell translational machinery. We also found that PRRSV-induced host translation shutoff was partly reversed by eliminating the effects of eIF2α phosphorylation or reactivating the mTOR pathway, indicating that PRRSV infection induces both eIF2α phosphorylation-dependent and -independent host translation shutoff.

Targeting mammalian target of rapamycin: prospects for the treatment of inflammatory bowel diseases

2020 ◽  
Vol 27 ◽  
Author(s):  
Naser-Aldin Lashgari ◽  
Nazanin Momeni Roudsari ◽  
Saeideh Momtaz ◽  
Negar Ghanaatian ◽  
Parichehr Kohansal ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Mammalian Target Of Rapamycin ◽  
Mtor Pathway ◽  
Mtor Signaling ◽  
Target Of Rapamycin ◽  
In Vivo Studies ◽  
Cochrane Library ◽  
Mtor Signaling Pathway ◽  
Inflammatory Bowel

: Inflammatory bowel disease (IBD) is a general term for a group of chronic and progressive disorders. Several cellular and biomolecular pathways are implicated in the pathogenesis of IBD, yet the etiology is unclear. Activation of the mammalian target of rapamycin (mTOR) pathway in the intestinal epithelial cells was also shown to induce inflammation. This review focuses on the inhibition of the mTOR signaling pathway and its potential application in treating IBD. We also provide an overview on plant-derived compounds that are beneficial for the IBD management through modulation of the mTOR pathway. Data were extracted from clinical, in vitro and in vivo studies published in English between 1995 and May 2019, which were collected from PubMed, Google Scholar, Scopus and Cochrane library databases. Results of various studies implied that inhibition of the mTOR signaling pathway downregulates the inflammatory processes and cytokines involved in IBD. In this context, a number of natural products might reverse the pathological features of the disease. Furthermore, mTOR provides a novel drug target for IBD. Comprehensive clinical studies are required to confirm the efficacy of mTOR inhibitors in treating IBD.

scholarly journals The polyphenol/saponin-rich Rhus tripartita extract has an apoptotic effect on THP-1 cells through the PI3K/AKT/mTOR signaling pathway

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Hajer Tlili ◽  
Anca Macovei ◽  
Daniela Buonocore ◽  
Manuela Lanzafame ◽  
Hanen Najjaa ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Plant Extract ◽  
Therapeutic Potential ◽  
Mtor Pathway ◽  
Mtor Signaling ◽  
Cellular Growth ◽  
Cancer Drug ◽  
Mtor Signaling Pathway ◽  
Epicatechin Gallate ◽  
Saponin Content

Abstract Background Hyperactivation of mechanistic target of rapamycin (mTOR) signaling pathway is involved in the regulation of cellular growth, proliferation, and more in general, is a common phenomenon in most types of cancers. Thus, natural substances targeting this pathway can be of great therapeutic potential in supporting the treatment of tumor patients. Rhus tripartita (Ucria) Grande is a plant growing in desertic areas which is traditionally used for the treatment of several diseases in Tunisia. In the present work, the biochemical profile of the main compounds present in the plant leaf extract was determined and the anti-leukemic potential of the plant extracts against acute monocytic leukaemia (AML) THP-1 cells was investigated. Methods After HPLC identification of some phenolic compounds present in the plant extract and the quantification of saponin content, the cytotoxic effect of Rhus tripartita extracts on THP-1 cell culture was evaluated using the colorimetric MTT assay for cell viability. THP-1 cells were incubated with medium containing the relative IC50 concentrations of total plant extract, saponin extract and some standard compounds (rutin (R); kaempferol (K); mixture of catechin, epicatechin, and epicatechin-gallate (CEEG); ellagic acid (EA). Finally, qRT-PCR and western blotting analysis were used to evaluate the effect of some flavonoids present in a crude extract of polyphenols and the total extract of saponins on cell survival and apoptosis. Results Analysis of expression level of some gene (PIK3CA, PTEN, AKT1, mTOR, EIF4E, RPS6KB1, and TSC1) involved in the mTOR pathway and the phosphorylation of S6 and AKT proteins allowed to observe that a total Rhus tripartita extract and some of the compounds found in the extract controls THP-1 cell proliferation and apoptosis via regulation of the PI3K-Akt-mTOR signaling pathway. Conclusion Rhus tripartita-induced inhibition of cell cycle and induction of apoptosis may involve the mTOR pathway. Therefore, Rhus tripartita extract may be a useful candidate as a natural anti-cancer drug to support the treatment of AML.

scholarly journals Nox4 Mediates RANKL-induced ER-Phagy and Osteoclastogenesis via Activating ROS/PERK/eIF-2α/ATF4 Pathway

2020 ◽  
Author(s):  
Jing Sun ◽  
wugui chen ◽  
Songtao Li ◽  
Sizhen Yang ◽  
Ying Zhang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Bone Resorption ◽  
Signaling Pathway ◽  
Molecular Mechanisms ◽  
Nuclear Factor Κb ◽  
Protein Levels ◽  
Unfolded Protein ◽  
Regulatory Effects ◽  
Protein Response

Abstract Background: Receptor activator of nuclear factor-κB ligand (RANKL) has been found to induce osteoclastogenesis and bone resorption. However, the underlying molecular mechanisms remain unclear. Methods: Osteoclastogenesis was evaluated by number of TRAP-positive multinuclear (≥3) osteoclasts, bone resorption pits and expression levels of related genes. Autophagy activity were evaluated by LC3-II/LC3-I ratio, number of autophagic vacuoles and adenovirus-mRFP-GFP-tagged LC3 reporting system; Inhibitor chloroquine (CQ) was used to verified the role of autophagy in RANKL-induced osteoclastogenesis; Via downregulating Nox4 with inhibitor (DPI) and retrovirus-conveyed shRNA, we further explored the importance of Nox4 in RANKL-induced autophagy and osteoclastogenesis, as well as the regulatory effects of Nox4 on nonmitochondrial reactive oxygen species (ROS) and PERK/eIF-2α/ATF4 pathway. Intracellular ROS scavenger (NAC), mitochondrial-targeted antioxidant (MitoTEMPO) and inhibitor of PERK (GSK2606414) were also employed to investigate the role of ROS and PERK/eIF-2α/ATF4 pathway in RANKL-induced autophagy and osteoclastogenesis. Results: RANKL markedly increased autophagy, while CQ treatment caused reduction of RANKL-induced autophagy and osteoclastogenesis. Consistent with the increased autophagy, the protein levels of Nox4 were significantly increased, and Nox4 was selectively localized within the endoplasmic reticulum (ER) after RANKL stimulation. DPI and shRNA efficiently decreased the protein level and (or) activity of Nox4 in the ER and inhibited RANKL-induced autophagy and osteoclastogenesis. Mechanistically, we found that Nox4 regulates RANKL-induced autophagy activation and osteoclastogenesis by stimulating the production of nonmitochondrial ROS. Additionally, Nox4-derived nonmitochondrial ROS dramatically activate PERK/eIF-2α/ATF4, which is a critical unfolded protein response (UPR)-related signaling pathway during ER stress. Blocking the activation of the PERK/eIF-2α/ATF4 signaling pathway either by Nox4 shRNA, ROS antioxidant or PERK inhibitor (GSK2606414) treatment significantly inhibited endoplasmic reticulum autophagy (ER-phagy) during RANKL-induced osteoclastogenesis. Conclusions: Our findings provide new insights into the processes of RANKL-induced osteoclastogenesis and will help the development of new therapeutic strategies for osteoclastogenesis-related diseases.

scholarly journals Dysregulation in the Unfolded Protein Response in the FGR Rat Pancreas

2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Xiaomei Liu ◽  
Yanyan Guo ◽  
Jun Wang ◽  
Liangliang Zhu ◽  
Linlin Gao
Keyword(s):  
Protein Kinase ◽  
Unfolded Protein Response ◽  
Binding Protein ◽  
Protein Kinase R ◽  
Pregnant Rats ◽  
Fetal Pancreas ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Upr Pathway

Accumulating evidence suggests that fetal growth restriction (FGR) leads to the development of diabetes mellitus in adults. The aim of this study was to investigate the effect of protein malnutrition in utero on the pancreatic unfolded protein response (UPR) pathway in FGR offspring. An FGR model was developed by feeding a low-protein diet to pregnant rats throughout gestation. Eighty-four UPR pathway components in the pancreas were investigated by quantitative PCR arrays and confirmed by qPCR and western blotting. Activating transcription factor (Atf4 and Atf6), herpud1, protein kinase R-like endoplasmic reticulum kinase (Perk), X-box binding protein 1 (Xbp1), and the phosphorylation of eIF2α were upregulated, while cyclic AMP-responsive element-binding protein 3-like protein was markedly downregulated in FGR fetuses compared with controls. Investigation in adult offspring revealed temporal changes, for most UPR factors restored to normal, except that dysregulation of Atf6 and Creb3l3 maintained until adulthood. Moreover, autophagy was suppressed in FGR fetal pancreas and may be associated with decreased activation of AMP-activated protein kinase (Ampk). Apoptosis regulators Bax and cleaved-caspase 3 and 9 were upregulated in FGR fetal pancreas. Given that islet size and number were decreased in FGR fetus, we speculated that the aberrant intrauterine milieu impaired UPR signaling in fetal pancreas development. Whether these alterations early in life contribute to the predisposition of FGR fetuses to adult metabolic disorders invites further exploration.

scholarly journals Effect of p38 Mitogen-Activated Protein Kinase on the Replication of Encephalomyocarditis Virus

2003 ◽  
Vol 77 (10) ◽  
pp. 5649-5656 ◽  
Author(s):  
Kensuke Hirasawa ◽  
Angus Kim ◽  
Hye-Seung Han ◽  
Jaeseok Han ◽  
Hee-Sook Jun ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Tyrosine Kinase ◽  
Viral Replication ◽  
Viral Infection ◽  
P38 Mapk ◽  
Viral Rna ◽  
Luciferase Reporter ◽  
L929 Cells ◽  
Emc Virus ◽  
Mitogen Activated Protein

ABSTRACT Cellular phosphorylation events during viral infection are necessary for effective viral replication. Encephalomyocarditis (EMC) virus has been used for studies on the molecular mechanisms of viral replication, but little is known about the cellular signaling pathways involved. This investigation was initiated to determine whether mitogen-activated protein kinases (MAPKs), which are central components of signal transduction pathways in the regulation of cell proliferation, play a role in the replication of EMC virus. We examined the phosphorylation of MAPKs, including extracellular signal-regulated kinase (ERK1/2), p38 MAPK, and stress-activated protein kinase 1/c-Jun NH2-terminal kinase (SAPK/JNK) in EMC virus-infected L929 cells and found that p38 MAPK and SAPK-JNK, but not ERK1/2, were activated during viral infection. We then examined the effect of these kinases on the replication of EMC virus in L929 cells by using specific inhibitors, including genistein or herbimycin A for tyrosine kinase, SB203580 or SB202190 for p38 MAPK, and PD98059 for ERK1/2. We found that the tyrosine kinase and p38 MAPK inhibitors, but not the ERK1/2 inhibitor, suppressed viral replication and that the inhibitory effect was primarily on viral protein synthesis. Finally, we examined whether p38 MAPK is involved in the translation of EMC viral transcripts by using L929 cells transfected with a gene construct containing the internal ribosomal entry site (IRES) of EMC virus and a luciferase reporter gene. We found that the p38 MAPK inhibitor suppressed the translation of EMC viral RNA. On the basis of these observations, we conclude that p38 MAPK plays a critical role in the replication of EMC virus, probably in the translation of viral RNA.

p38 mitogen-activated protein kinase inhibits calcium-dependent chloride secretion in T84 colonic epithelial cells

2003 ◽  
Vol 284 (2) ◽  
pp. C339-C348 ◽  
Author(s):  
Stephen J. Keely ◽  
Kim E. Barrett
Keyword(s):  
Protein Kinase ◽  
Epithelial Cells ◽  
Signaling Pathway ◽  
P38 Mapk ◽  
Mitogen Activated Protein Kinase ◽  
Muscarinic Agonist ◽  
Colonic Epithelial Cells ◽  
Mitogen Activated Protein ◽  
Intracellular Ca ◽  
Sb 203580

We have previously shown that Ca2+-dependent Cl−secretion across intestinal epithelial cells is limited by a signaling pathway involving transactivation of the epidermal growth factor receptor (EGFR) and activation of ERK mitogen-activated protein kinase (MAPK). Here, we have investigated a possible role for p38 MAPK in regulation of Ca2+-dependent Cl− secretion. Western blot analysis of T84 colonic epithelial cells revealed that the muscarinic agonist carbachol (CCh; 100 μM) stimulated phosphorylation and activation of p38 MAPK. The p38 inhibitor SB-203580 (10 μM) potentiated and prolonged short-circuit current ( I sc) responses to CCh across voltage-clamped T84 cells to 157.4 ± 6.9% of those in control cells ( n = 21; P < 0.001). CCh-induced p38 phosphorylation was attenuated by the EGFR inhibitor tyrphostin AG-1478 (0.1 nM–10 μM) and by the Src family kinase inhibitor PP2 (20 nM–2 μM). The effects of CCh on p38 phosphorylation were mimicked by thapsigargin (TG; 2 μM), which specifically elevates intracellular Ca2+, and were abolished by the Ca2+ chelator BAPTA-AM (20 μM), implying a role for intracellular Ca2+ in mediating p38 activation. SB-203580 (10 μM) potentiated I sc responses to TG to 172.4 ± 18.1% of those in control cells ( n= 18; P < 0.001). When cells were pretreated with SB-203580 and PD-98059 to simultaneously inhibit p38 and ERK MAPKs, respectively, I sc responses to TG and CCh were significantly greater than those observed with either inhibitor alone. We conclude that Ca2+-dependent agonists stimulate p38 MAPK in T84 cells by a mechanism involving intracellular Ca2+, Src family kinases, and the EGFR. CCh-stimulated p38 activation constitutes a similar, but distinct and complementary, antisecretory signaling pathway to that of ERK MAPK.

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