Adaptation to Endoplasmic Reticulum Stress in Candida albicans Relies on the Activity of the Hog1 Mitogen-Activated Protein Kinase

Adaptation to ER stress is linked to the pathogenicity of C. albicans. The fungus responds to ER stress primarily by activating the conserved Ire1-Hac1-dependent unfolded protein response (UPR) pathway. Subsequently, when ER homeostasis is re-established, the UPR is attenuated in a timely manner, a facet that is unexplored in C. albicans. Here, we show that C. albicans licenses the HOG (high-osmolarity glycerol) MAPK pathway for abating ER stress as evidenced by activation and translocation of Hog1 to the nucleus during tunicamycin-induced ER stress. We find that, once activated, Hog1 attenuates the activity of Ire1-dependent UPR, thus facilitating adaptation to ER stress. We use the previously established assay, where the disappearance of the UPR-induced spliced HAC1 mRNA correlates with the re-establishment of ER homeostasis, to investigate attenuation of the UPR in C. albicans. hog1Δ/Δ cells retain spliced HAC1 mRNA levels for longer duration reflecting the delay in attenuating Ire1-dependent UPR. Conversely, compromising the expression of Ire1 (ire1 DX mutant strain) results in diminished levels of phosphorylated Hog1, restating the cross-talk between Ire1 and HOG pathways. Phosphorylation signal to Hog1 MAP kinase is relayed through Ssk1 in response to ER stress as inactivation of Ssk1 abrogates Hog1 phosphorylation in C. albicans. Additionally, Hog1 depends on its cytosolic as well as nuclear activity for mediating ER stress-specific responses in the fungus. Our results show that HOG pathway serves as a point of cross-talk with the UPR pathway, thus extending the role of this signaling pathway in promoting adaptation to ER stress in C. albicans. Additionally, this study integrates this MAPK pathway into the little known frame of ER stress adaptation pathways in C. albicans.

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MKK3-p38 signaling promotes apoptosis and the early inflammatory response in the obstructed mouse kidney

AJP Renal Physiology ◽

10.1152/ajprenal.00010.2007 ◽

2007 ◽

Vol 293 (5) ◽

pp. F1556-F1563 ◽

Cited By ~ 44

Author(s):

Frank Y. Ma ◽

Greg H. Tesch ◽

Richard A. Flavell ◽

Roger J. Davis ◽

David J. Nikolic-Paterson

Keyword(s):

Inflammatory Response ◽

P38 Mapk ◽

Renal Injury ◽

Mapk Pathway ◽

Mitogen Activated Protein Kinase ◽

Mrna Levels ◽

Direct Role ◽

Mitogen Activated Protein ◽

Early Inflammatory Response ◽

Induced Apoptosis

Activation of the p38 mitogen-activated protein kinase (MAPK) pathway induces inflammation, apoptosis, and fibrosis. However, little is known of the contribution of the upstream kinases, MMK3 and MKK6, to activation of the p38 kinase in the kidney and consequent renal injury. This study investigated the contribution of MKK3 to p38 MAPK activation and renal injury in the obstructed kidney. Groups of eight wild-type (WT) or Mkk3−/− mice underwent unilateral ureteric obstruction (UUO) and were killed 3 or 7 days later. Western blotting showed a marked increase in phospho-p38 (p-p38) MAPK in UUO WT kidney. The same trend of increased p-p38 MAPK was seen in the UUO Mkk3−/− kidney, although the actual level of p-p38 MAPK was significantly reduced compared with WT, and this could not be entirely compensated for by the increase in MKK6 expression in the Mkk3−/− kidney. Apoptosis of tubular and interstitial cells in WT UUO mice was reduced by 50% in Mkk3−/− UUO mice. Furthermore, cultured Mkk3−/− tubular epithelial cells showed resistance to H2O2-induced apoptosis, suggesting a direct role for MKK3-p38 signaling in tubular apoptosis. Upregulation of MCP-1 mRNA levels and macrophage infiltration seen on day 3 in WT UUO mice was significantly reduced in Mkk3−/− mice, but this difference was not evident by day 7. The development of renal fibrosis in Mkk3−/− UUO mice was not different from that seen in WT UUO mice. In conclusion, these studies identify discrete roles for MKK3-p38 signaling in renal cell apoptosis and the early inflammatory response in the obstructed kidney.

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Control of the expression of inflammatory response genes

Biochemical Society Symposium ◽

10.1042/bss0700095 ◽

2003 ◽

Vol 70 ◽

pp. 95-106 ◽

Cited By ~ 91

Author(s):

Jeremy Saklatvala ◽

Jonathan Dean ◽

Andrew Clark

Keyword(s):

Gene Expression ◽

Transcription Factors ◽

Inflammatory Response ◽

Mapk Pathway ◽

Interleukin 1 ◽

Mitogen Activated Protein Kinase ◽

Mrna Levels ◽

Matrix Metalloproteinase 1 ◽

Inflammatory Stimuli ◽

Mitogen Activated Protein

The expression of genes involved in the inflammatory response is controlled both transcriptionally and post-transcriptionally. Primary inflammatory stimuli, such as microbial products and the cytokines interleukin-1 (IL-1) and tumour necrosis factor α (TNFα), act through receptors of either the Toll and IL-1 receptor (TIR) family or the TNF receptor family. These cause changes in gene expression by activating four major intracellular signalling pathways that are cascades of protein kinases: namely the three mitogen-activated protein kinase (MAPK) pathways, and the pathway leading to activation of the transcription factor nuclear factor ϰB (NFϰB). The pathways directly activate and induce the expression of a limited set of transcription factors which promote the transcription of inflammatory response genes. Many of the mRNAs are unstable, and are stabilized by the p38 MAPK pathway. Instability is mediated by clusters of the AUUUA motif in the 3″ untranslated regions of the mRNAs. Control of mRNA stability provides a means of increasing the amplitude of a response and allows rapid adjustment of mRNA levels. Not all mRNAs stabilized by p38 contain AUUUA clusters; for example, matrix metalloproteinase-1 and -3 mRNAs lack these clusters, but are stabilized. Inflammatory gene expression is inhibited by glucocorticoids. These suppress MAPK signalling by inducing a MAPK phosphatase. This may be a significant mechanism additional to that by which the glucocorticoid receptor interferes with transcription factors.

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Role of the Unfolded Protein Response in Regulating the Mucin-Dependent Filamentous-Growth Mitogen-Activated Protein Kinase Pathway

Molecular and Cellular Biology ◽

10.1128/mcb.01501-14 ◽

2015 ◽

Vol 35 (8) ◽

pp. 1414-1432 ◽

Cited By ~ 26

Author(s):

Hema Adhikari ◽

Nadia Vadaie ◽

Jacky Chow ◽

Lauren M. Caccamise ◽

Colin A. Chavel ◽

...

Keyword(s):

Protein Kinase ◽

Unfolded Protein Response ◽

Mapk Pathway ◽

Filamentous Growth ◽

Proteolytic Processing ◽

Mitogen Activated Protein Kinase ◽

Unfolded Protein ◽

Mitogen Activated Protein ◽

The Unfolded Protein Response ◽

Protein Response

Signaling mucins are evolutionarily conserved regulators of signal transduction pathways. The signaling mucin Msb2p regulates the Cdc42p-dependent mitogen-activated protein kinase (MAPK) pathway that controls filamentous growth in yeast. The cleavage and release of the glycosylated inhibitory domain of Msb2p is required for MAPK activation. We show here that proteolytic processing of Msb2p was induced by underglycosylation of its extracellular domain. Cleavage of underglycosylated Msb2p required the unfolded protein response (UPR), a quality control (QC) pathway that operates in the endoplasmic reticulum (ER). The UPR regulator Ire1p, which detects misfolded/underglycosylated proteins in the ER, controlled Msb2p cleavage by regulating transcriptional induction of Yps1p, the major protease that processes Msb2p. Accordingly, the UPR was required for differentiation to the filamentous cell type. Cleavage of Msb2p occurred in conditional trafficking mutants that trap secretory cargo in the endomembrane system. Processed Msb2p was delivered to the plasma membrane, and its turnover by the ubiquitin ligase Rsp5p and ESCRT attenuated the filamentous-growth pathway. We speculate that the QC pathways broadly regulate signaling glycoproteins and their cognate pathways by recognizing altered glycosylation patterns that can occur in response to extrinsic cues.

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Analysis of Mitogen-Activated Protein Kinase Signaling Specificity in Response to Hyperosmotic Stress: Use of an Analog-Sensitive HOG1 Allele

Eukaryotic Cell ◽

10.1128/ec.00037-06 ◽

2006 ◽

Vol 5 (8) ◽

pp. 1215-1228 ◽

Cited By ~ 56

Author(s):

Patrick J. Westfall ◽

Jeremy Thorner

Keyword(s):

Protein Kinase ◽

Cross Talk ◽

Kinase Activity ◽

Hyperosmotic Stress ◽

Mitogen Activated Protein Kinase ◽

Hog Pathway ◽

Pheromone Response ◽

Mapk Kinase ◽

Signaling Specificity ◽

Mitogen Activated Protein

ABSTRACT When confronted with a marked increase in external osmolarity, budding yeast (Saccharomyces cerevisiae) cells utilize a conserved mitogen-activated protein kinase (MAPK) signaling cascade (the high-osmolarity glycerol or HOG pathway) to elicit cellular responses necessary to permit continued growth. One input that stimulates the HOG pathway requires the integral membrane protein and putative osmosensor Sho1, which recruits and enables activation of the MAPK kinase kinase Ste11. In mutants that lack the downstream MAPK kinase (pbs2Δ) or the MAPK (hog1Δ) of the HOG pathway, Ste11 activated by hyperosmotic stress is able to inappropriately stimulate the pheromone response pathway. This loss of signaling specificity is known as cross talk. To determine whether it is the Hog1 polypeptide per se or its kinase activity that is necessary to prevent cross talk, we constructed a fully functional analog-sensitive allele of HOG1 to permit acute inhibition of this enzyme without other detectable perturbations of the cell. We found that the catalytic activity of Hog1 is required continuously to prevent cross talk between the HOG pathway and both the pheromone response and invasive growth pathways. Moreover, contrary to previous reports, we found that the kinase activity of Hog1 is necessary for its stress-induced nuclear import. Finally, our results demonstrate a role for active Hog1 in maintaining signaling specificity under conditions of persistently high external osmolarity.

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Distinct roles for extracellular-signal-regulated protein kinase (ERK) mitogen-activated protein kinases and phosphatidylinositol 3-kinase in the regulation of Mcl-1 synthesis

Biochemical Journal ◽

10.1042/bj3560473 ◽

2001 ◽

Vol 356 (2) ◽

pp. 473-480 ◽

Cited By ~ 28

Author(s):

Kathryn M. SCHUBERT ◽

Vincent DURONIO

Keyword(s):

Protein Kinase ◽

Mapk Pathway ◽

Family Members ◽

Protein Translation ◽

Mitogen Activated Protein Kinase ◽

Mrna Levels ◽

Phosphatidylinositol 3 Kinase ◽

Extracellular Signal ◽

Mitogen Activated Protein ◽

Phosphatidylinositol 3

Alterations in the expression of various Bcl-2 family members may act as one means by which a cell's survival may be regulated. The mechanism by which cytokines regulate expression of Bcl-2 family members was examined in the haemopoietic cell line TF-1. Cytokine-induced Mcl-1 protein expression was shown to be controlled through a pathway dependent upon phosphatidylinositol 3-kinase (PI 3-kinase). The cytokine-induced increase in mRNA transcription was not dependent upon PI 3-kinase, thus dissociating the immediate-early transcription factors responsible for Mcl-1 transcription from the PI 3-kinase signalling pathway. In contrast, Mcl-1 mRNA levels were dependent upon MEK [mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated protein kinase kinase] activation, suggesting a role for the Ras/MEK/MAPK pathway in Mcl-1 transcription. Activation of PI 3-kinase was shown to be necessary to stimulate Mcl-1 protein translation. This was not due to any effect on prolonging the half-life of the protein. Finally, the lipid second messenger ceramide was shown to cause a reduction in Mcl-1 protein translation, probably via its ability to inhibit protein kinase B activation, providing further clues regarding the death-inducing effect of this lipid.

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Unique and Redundant Roles for HOG MAPK Pathway Components as Revealed by Whole-Genome Expression Analysis

Molecular Biology of the Cell ◽

10.1091/mbc.e03-07-0521 ◽

2004 ◽

Vol 15 (2) ◽

pp. 532-542 ◽

Cited By ~ 164

Author(s):

Sean M. O'Rourke ◽

Ira Herskowitz

Keyword(s):

Protein Kinase ◽

Mapk Pathway ◽

Mitogen Activated Protein Kinase ◽

Whole Genome ◽

Hog Pathway ◽

General Stress Response ◽

High Osmolarity ◽

Genome Expression ◽

Mitogen Activated Protein ◽

Whole Genome Expression

The Saccharomyces cerevisiae high osmolarity glycerol (HOG) mitogen-activated protein kinase pathway is required for osmoadaptation and contains two branches that activate a mitogen-activated protein kinase (Hog1) via a mitogen-activated protein kinase kinase (Pbs2). We have characterized the roles of common pathway components (Hog1 and Pbs2) and components in the two upstream branches (Ste11, Sho1, and Ssk1) in response to elevated osmolarity by using whole-genome expression profiling. Several new features of the HOG pathway were revealed. First, Hog1 functions during gene induction and repression, cross talk inhibition, and in governing the regulatory period. Second, the phenotypes of pbs2 and hog1 mutants are identical, indicating that the sole role of Pbs2 is to activate Hog1. Third, the existence of genes whose induction is dependent on Hog1 and Pbs2 but not on Ste11 and Ssk1 suggests that there are additional inputs into Pbs2 under our inducing conditions. Fourth, the two upstream pathway branches are not redundant: the Sln1-Ssk1 branch has a much more prominent role than the Sho1-Ste11 branch for activation of Pbs2 by modest osmolarity. Finally, the general stress response pathway and both branches of the HOG pathway all function at high osmolarity. These studies demonstrate that cells respond to increased osmolarity by using different signal transduction machinery under different conditions.

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Cross-talk between mitogenic Ras/MAPK and survival PI3K/Akt pathways: a fine balance

Biochemical Society Transactions ◽

10.1042/bst20110609 ◽

2012 ◽

Vol 40 (1) ◽

pp. 139-146 ◽

Cited By ~ 256

Author(s):

Edita Aksamitiene ◽

Anatoly Kiyatkin ◽

Boris N. Kholodenko

Keyword(s):

Growth Factors ◽

Cross Talk ◽

Mapk Pathway ◽

Pi3k Pathway ◽

Negative Influence ◽

Positive Influence ◽

Mitogen Activated Protein Kinase ◽

Mitogen Activated Protein ◽

High Doses ◽

Phosphoinositide 3 Kinase

In the present paper, we describe multiple levels of cross-talk between the PI3K (phosphoinositide 3-kinase)/Akt and Ras/MAPK (mitogen-activated protein kinase) signalling pathways. Experimental data and computer simulations demonstrate that cross-talk is context-dependent and that both pathways can activate or inhibit each other. Positive influence of the PI3K pathway on the MAPK pathway is most effective at sufficiently low doses of growth factors, whereas negative influence of the MAPK pathway on the PI3K pathway is mostly pronounced at high doses of growth factors. Pathway cross-talk endows a cell with emerging capabilities for processing and decoding signals from multiple receptors activated by different combinations of extracellular cues.

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Ptc1, a Type 2C Ser/Thr Phosphatase, Inactivates the HOG Pathway by Dephosphorylating the Mitogen-Activated Protein Kinase Hog1

Molecular and Cellular Biology ◽

10.1128/mcb.21.1.51-60.2001 ◽

2001 ◽

Vol 21 (1) ◽

pp. 51-60 ◽

Cited By ~ 136

Author(s):

Janel Warmka ◽

Jennifer Hanneman ◽

Ji Lee ◽

Dipesh Amin ◽

Irene Ota

Keyword(s):

Protein Kinase ◽

Osmotic Stress ◽

Metal Ion ◽

Mapk Pathway ◽

Negative Regulator ◽

Mitogen Activated Protein Kinase ◽

Hog Pathway ◽

Mitogen Activated Protein

ABSTRACT The HOG (high-osmolarity glycerol) mitogen-activated protein kinase (MAPK) pathway regulates the osmotic stress response in the yeast Saccharomyces cerevisiae. Three type 2C Ser/Thr phosphatases (PTCs), Ptc1, Ptc2, and Ptc3, have been isolated as negative regulators of this pathway. Previously, multicopy expression of PTC1 and PTC3 was shown to suppress lethality of the sln1Δ strain due to hyperactivation of the HOG pathway. In this work, we show thatPTC2 also suppresses sln1Δ lethality. Furthermore, the phosphatase activity of these PTCs was needed for suppression, as mutation of a conserved Asp residue, likely to coordinate a metal ion, inactivated PTCs. Further analysis of Ptc1 function in vivo showed that it inactivates the MAPK, Hog1, but not the MEK, Pbs2. In the wild type, Hog1 kinase activity increased transiently, ∼12-fold in response to osmotic stress, while overexpression of PTC1 limited activation to ∼3-fold. In contrast, overexpression of PTC1 did not inhibit phosphorylation of Hog1 Tyr in the phosphorylation lip, suggesting that Ptc1 does not act on Pbs2. Deletion of PTC1 also strongly affected Hog1, leading to high basal Hog1 activity and sustained Hog1 activity in response to osmotic stress, the latter being consistent with a role for Ptc1 in adaptation. In vitro, Ptc1 but not the metal binding site mutant, Ptc1D58N, inactivated Hog1 by dephosphorylating the phosphothreonine but not the phosphotyrosine residue in the phosphorylation lip. Consistent with its role as a negative regulator of Hog1, which accumulates in the nucleus upon activation, Ptc1 was found in both the nucleus and the cytoplasm. Thus, one function of Ptc1 is to inactivate Hog1.

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Stbd1 promotes glycogen clustering during endoplasmic reticulum stress and supports survival of mouse myoblasts

Journal of Cell Science ◽

10.1242/jcs.244855 ◽

2020 ◽

Vol 133 (20) ◽

pp. jcs244855

Author(s):

Andria A. Lytridou ◽

Anthi Demetriadou ◽

Melina Christou ◽

Louiza Potamiti ◽

Nikolas P. Mastroyiannopoulos ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Er Stress ◽

Myogenic Differentiation ◽

Apoptotic Pathway ◽

Unfolded Protein ◽

The Unfolded Protein Response ◽

Glucose Restriction ◽

Protein Response ◽

Er Homeostasis ◽

Upr Pathway

ABSTRACTImbalances in endoplasmic reticulum (ER) homeostasis provoke a condition known as ER stress and activate the unfolded protein response (UPR) pathway, an evolutionarily conserved cell survival mechanism. Here, we show that mouse myoblasts respond to UPR activation by stimulating glycogenesis and the formation of α-amylase-degradable, glycogen-containing ER structures. We demonstrate that the glycogen-binding protein Stbd1 is markedly upregulated through the PERK signalling branch of the UPR pathway and is required for the build-up of glycogen structures in response to ER stress activation. In the absence of ER stress, Stbd1 overexpression is sufficient to induce glycogen clustering but does not stimulate glycogenesis. Glycogen structures induced by ER stress are degraded under conditions of glucose restriction through a process that does not depend on autophagosome–lysosome fusion. Furthermore, we provide evidence that failure to induce glycogen clustering during ER stress is associated with enhanced activation of the apoptotic pathway. Our results reveal a so far unknown response of mouse myoblasts to ER stress and uncover a novel specific function of Stbd1 in this process, which may have physiological implications during myogenic differentiation.This article has an associated First Person interview with the first author of the paper.

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Atf1 Is a Target of the Mitogen-activated Protein Kinase Pmk1 and Regulates Cell Integrity in Fission Yeast

Molecular Biology of the Cell ◽

10.1091/mbc.e07-03-0282 ◽

2007 ◽

Vol 18 (12) ◽

pp. 4794-4802 ◽

Cited By ~ 40

Author(s):

Hirofumi Takada ◽

Masayuki Nishimura ◽

Yuta Asayama ◽

Yoshiaki Mannse ◽

Shunji Ishiwata ◽

...

Keyword(s):

Protein Kinase ◽

Fission Yeast ◽

Mapk Pathway ◽

Mapk Signaling ◽

Negative Regulator ◽

Mitogen Activated Protein Kinase ◽

Mrna Levels ◽

Cell Integrity ◽

Dual Specificity ◽

Mitogen Activated Protein

In fission yeast, knockout of the calcineurin gene resulted in hypersensitivity to Cl−, and the overexpression of pmp1+ encoding a dual-specificity phosphatase for Pmk1 mitogen-activated protein kinase (MAPK) or the knockout of the components of the Pmk1 pathway complemented the Cl− hypersensitivity of calcineurin deletion. Here, we showed that the overexpression of ptc1+ and ptc3+, both encoding type 2C protein phosphatase (PP2C), previously known to inactivate the Wis1–Spc1–Atf1 stress-activated MAPK signaling pathway, suppressed the Cl− hypersensitivity of calcineurin deletion. We also demonstrated that the mRNA levels of these two PP2Cs and pyp2+, another negative regulator of Spc1, are dependent on Pmk1. Notably, the deletion of Atf1, but not that of Spc1, displayed hypersensitivity to the cell wall-damaging agents and also suppressed the Cl− hypersensitivity of calcineurin deletion, both of which are characteristic phenotypes shared by the mutation of the components of the Pmk1 MAPK pathway. Moreover, micafungin treatment induced Pmk1 hyperactivation that resulted in Atf1 hyperphosphorylation. Together, our results suggest that PP2C is involved in a negative feedback loop of the Pmk1 signaling, and results also demonstrate that Atf1 is a key component of the cell integrity signaling downstream of Pmk1 MAPK.

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