scholarly journals Actin Recovery and Bud Emergence in Osmotically Stressed Cells Requires the Conserved Actin Interacting Mitogen-activated Protein Kinase Kinase Kinase Ssk2p/MTK1 and the Scaffold Protein Spa2p

2003 ◽  
Vol 14 (7) ◽  
pp. 3013-3026 ◽  
Author(s):  
Tatiana Yuzyuk ◽  
David C. Amberg
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Osmotic Stress ◽  
Scaffold Protein ◽  
Mitogen Activated Protein Kinase ◽  
Yeast Cells ◽  
High Osmolarity ◽  
Mitogen Activated Protein ◽  
Stressed Cells ◽  
Protein Kinase Kinase

Osmotic stress causes actin cytoskeleton disassembly, a cell cycle arrest, and activation of the high osmolarity growth mitogen-activated protein kinase pathway. A previous study showed that Ssk2p, a mitogen-activated protein kinase kinase kinase of the high osmolarity growth pathway, promotes actin cytoskeleton recovery to the neck of late cell cycle, osmotically stressed yeast cells. Data presented herein examined the role of Ssk2p in actin recovery early in the cell cycle. We found that actin recovery at all stages of the cell cycle is not controlled by Ssk1p, the known activator of Ssk2p, but required a polarized distribution of Ssk2p as well as its actin-interacting and kinase activity. Stress-induced localization of Ssk2p to the neck required the septin Shs1p, whereas localization to the bud cortex depended on the polarity scaffold protein Spa2p. spa2Δ cells, like ssk2Δ cells, were defective for actin recovery from osmotic stress. These spa2Δ defects could be suppressed by overexpression of catalytically active Ssk2p. Furthermore, Spa2p could be precipitated by GST-Ssk2p from extracts of osmotically stressed cells. The Ssk2p mediated actin recovery pathway seems to be conserved; MTK1, a human mitogen-activated protein kinase kinase kinase of the p38 stress response pathway and Ssk2p homolog, was also able to localize at polarized growth sites, form a complex with actin and Spa2p, and complement actin recovery defects in osmotically stressed ssk2Δ and spa2Δ yeast cells. We hypothesize that osmotic stress-induced actin disassembly leads to the formation of an Ssk2p–actin complex and the polarized localization of Ssk2p. Polarized Ssk2p associates with the scaffold protein Spa2p in the bud and Shs1p in the neck, allowing Ssk2p to regulate substrates involved in polarized actin assembly.

scholarly journals Regulation of the Saccharomyces cerevisiae HOG1 mitogen-activated protein kinase by the PTP2 and PTP3 protein tyrosine phosphatases.

1997 ◽  
Vol 17 (3) ◽  
pp. 1289-1297 ◽  
Author(s):  
S M Wurgler-Murphy ◽  
T Maeda ◽  
E A Witten ◽  
H Saito
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Mitogen Activated Protein Kinase ◽  
Yeast Cells ◽  
High Osmolarity ◽  
Mapk Kinase ◽  
Protein Tyrosine ◽  
Mitogen Activated Protein

In response to increases in extracellular osmolarity, Saccharomyces cerevisiae activates the HOG1 mitogen-activated protein kinase (MAPK) cascade, which is composed of a pair of redundant MAPK kinase kinases, namely, Ssk2p and Ssk22p, the MAPK kinase Pbs2p, and the MAPK Hog1p. Hog1p is activated by Pbs2p through phosphorylation of specific threonine and tyrosine residues. Activated Hog1p is essential for survival of yeast cells at high osmolarity. However, expression of constitutively active mutant kinases, such as those encoded by SSK2deltaN and PBS2(DD), is toxic and results in a lethal level of Hog1p activation. Overexpression of the protein tyrosine phosphatase Ptp2p suppresses the lethality of these mutations by dephosphorylating Hog1p. A catalytically inactive Cys-to-Ser Ptp2p mutant (Ptp2(C/S)p) is tightly bound to tyrosine-phosphorylated Hog1p in vivo. Disruption of PTP2 leads to elevated levels of tyrosine-phosphorylated Hog1p following exposure of cells to high osmolarity. Disruption of both PTP2 and another protein tyrosine phosphatase gene, PTP3, results in constitutive Hog1p tyrosine phosphorylation even in the absence of increased osmolarity. Thus, Ptp2p and Ptp3p are the major phosphatases responsible for the tyrosine dephosphorylation of Hog1p. When catalytically inactive Hog1(K/N)p is expressed in hog1delta cells, it is constitutively tyrosine phosphorylated. In contrast, Hog1(K/N)p, expressed together with wild-type Hog1p, is tyrosine phosphorylated only when cells are exposed to high osmolarity. Thus, the kinase activity of Hog1p is required for its own tyrosine dephosphorylation. Northern blot analyses suggest that Hog1p regulates Ptp2p and/or Ptp3p activity at the posttranscriptional level.

scholarly journals Mitogen-activated protein kinase kinase activity is required for the G2/M transition of the cell cycle in mammalian fibroblasts

1999 ◽  
Vol 96 (20) ◽  
pp. 11335-11340 ◽  
Author(s):  
J. H. Wright ◽  
E. Munar ◽  
D. R. Jameson ◽  
P. R. Andreassen ◽  
R. L. Margolis ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Kinase Activity ◽  
Mitogen Activated Protein Kinase ◽  
Mitogen Activated Protein ◽  
Protein Kinase Kinase

scholarly journals Rck2 Kinase Is a Substrate for the Osmotic Stress-Activated Mitogen-Activated Protein Kinase Hog1

2000 ◽  
Vol 20 (11) ◽  
pp. 3887-3895 ◽  
Author(s):  
Elizabeth Bilsland-Marchesan ◽  
Joaquín Ariño ◽  
Haruo Saito ◽  
Per Sunnerhagen ◽  
Francesc Posas
Keyword(s):  
Protein Kinase ◽  
Osmotic Stress ◽  
Mitogen Activated Protein Kinase ◽  
Yeast Cells ◽  
Dependent Manner ◽  
Mapk Activation ◽  
Mitogen Activated Protein ◽  
Two Hybrid

ABSTRACT Exposure of yeast cells to increases in extracellular osmolarity activates the Hog1 mitogen-activated protein kinase (MAPK). Activation of Hog1 MAPK results in induction of a set of osmoadaptive responses, which allow cells to survive in high-osmolarity environments. Little is known about how the MAPK activation results in induction of these responses, mainly because no direct substrates for Hog1 have been reported. We conducted a two-hybrid screening using Hog1 as a bait to identify substrates for the MAPK, and the Rck2 protein kinase was identified as an interactor for Hog1. Both two-hybrid analyses and coprecipitation assays demonstrated that Hog1 binds strongly to the C-terminal region of Rck2. Upon osmotic stress, Rck2 was phosphorylated in vivo in a Hog1-dependent manner. Furthermore, purified Hog1 was able to phosphorylate Rck2 when activated both in vivo and in vitro. Rck2 phosphorylation occurred specifically at Ser519, a residue located within the C-terminal putative autoinhibitory domain. Interestingly, phosphorylation at Ser519 by Hog1 resulted in an increase of Rck2 kinase activity. Overexpression of Rck2 partially suppressed the osmosensitive phenotype of hog1Δ and pbs2Δ cells, suggesting that Rck2 is acting downstream of Hog1. Consistently, growth arrest caused by hyperactivation of the Hog1 MAPK was abolished by deletion of the RCK2 gene. Furthermore, overexpression of a catalytically impaired (presumably dominant inhibitory) Rck2 kinase resulted in a decrease of osmotolerance in wild-type cells but not in hog1Δ cells. Taken together, our data suggest that Rck2 acts downstream of Hog1, controlling a subset of the responses induced by the MAPK upon osmotic stress.

scholarly journals Mitogen-activated Protein Kinase Kinase 1-dependent Golgi Unlinking Occurs in G2 Phase and Promotes the G2/M Cell Cycle Transition

2007 ◽  
Vol 18 (2) ◽  
pp. 594-604 ◽  
Author(s):  
Timothy N. Feinstein ◽  
Adam D. Linstedt
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Specific Inhibitor ◽  
Cell Cycle Checkpoint ◽  
Mitogen Activated Protein Kinase ◽  
M Cell ◽  
M Phase ◽  
Mitogen Activated Protein ◽  
Cell Cycle Transition ◽  
Protein Kinase Kinase

Two controversies have emerged regarding the signaling pathways that regulate Golgi disassembly at the G2/M cell cycle transition. The first controversy concerns the role of mitogen-activated protein kinase activator mitogen-activated protein kinase kinase (MEK)1, and the second controversy concerns the participation of Golgi structure in a novel cell cycle “checkpoint.” A potential simultaneous resolution is suggested by the hypothesis that MEK1 triggers Golgi unlinking in late G2 to control G2/M kinetics. Here, we show that inhibition of MEK1 by RNA interference or by using the MEK1/2-specific inhibitor U0126 delayed the passage of synchronized HeLa cells into M phase. The MEK1 requirement for normal mitotic entry was abrogated if Golgi proteins were dispersed before M phase by treatment of cells with brefeldin A or if GRASP65, which links Golgi stacks into a ribbon network, was depleted. Imaging revealed that unlinking of the Golgi apparatus begins before M phase, is independent of cyclin-dependent kinase 1 activation, and requires MEK signaling. Furthermore, expression of the GRASP family member GRASP55 after alanine substitution of its MEK1-dependent mitotic phosphorylation sites inhibited both late G2 Golgi unlinking and the G2/M transition. Thus, MEK1 plays an in vivo role in Golgi reorganization, which regulates cell cycle progression.

ZmMKK3, a novel maize group B mitogen-activated protein kinase kinase gene, mediates osmotic stress and ABA signal responses

2012 ◽  
Vol 169 (15) ◽  
pp. 1501-1510 ◽  
Author(s):  
Maoying Zhang ◽  
Jiaowen Pan ◽  
Xiangpei Kong ◽  
Yan Zhou ◽  
Yang Liu ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Osmotic Stress ◽  
Mitogen Activated Protein Kinase ◽  
Kinase Gene ◽  
Mitogen Activated Protein ◽  
Group B ◽  
Protein Kinase Kinase

scholarly journals Targeting the MEF2-Like Transcription Factor Smp1 by the Stress-Activated Hog1 Mitogen-Activated Protein Kinase

2003 ◽  
Vol 23 (1) ◽  
pp. 229-237 ◽  
Author(s):  
Eulàlia de Nadal ◽  
Laura Casadomé ◽  
Francesc Posas
Keyword(s):  
Transcription Factor ◽  
Protein Kinase ◽  
Osmotic Stress ◽  
Stationary Phase ◽  
Osmotic Shock ◽  
Critical Role ◽  
Mitogen Activated Protein Kinase ◽  
Yeast Cells ◽  
Dependent Manner ◽  
Mitogen Activated Protein

ABSTRACT Exposure of Saccharomyces cerevisiae to increases in extracellular osmolarity activates the stress-activated Hog1 mitogen-activated protein kinase (MAPK), which is essential for cell survival upon osmotic stress. Yeast cells respond to osmotic stress by inducing the expression of a very large number of genes, and the Hog1 MAPK plays a critical role in gene transcription upon stress. To understand how Hog1 controls gene expression, we designed a genetic screen to isolate new transcription factors under the control of the MAPK and identified the MEF2-like transcription factor, Smp1, as a target for Hog1. Overexpression of SMP1 induced Hog1-dependent expression of osmoresponsive genes such as STL1, whereas smp1Δ cells were defective in their expression. Consistently, smp1Δ cells displayed reduced viability upon osmotic shock. In vivo coprecipitation and phosphorylation studies showed that Smp1 and Hog1 interact and that Smp1 is phosphorylated upon osmotic stress in a Hog1-dependent manner. Hog1 phosphorylated Smp1 in vitro at the C-terminal region. Phosphorylation of Smp1 by the MAPK is essential for its function, since a mutant allele unable to be phosphorylated by the MAPK displays impaired stress responses. Thus, our data indicate that Smp1 acts downstream of Hog1, controlling a subset of the responses induced by the MAPK. Moreover, Smp1 concentrates in the nucleus during the stationary phase, and the lack of SMP1 results in cells that lose viability in the stationary phase. Localization of Smp1 depends on HOG1, and consistently, hog1Δ cells also lose viability during this growth phase. These data suggest that Smp1 could be mediating a role for the Hog1 MAPK during the stationary phase.

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