Constitutive activation of the Saccharomyces cerevislae mating response pathway by a MAP kinase kinase from Candida albicans

Eight alleles of Dsor1 encoding a Drosophila homologue of mitogen-activated protein (MAP) kinase kinase were obtained as dominant suppressors of the MAP kinase kinase kinase D-raf. These Dsor1 alleles themselves showed no obvious phenotypic consequences nor any effect on the viability of the flies, although they were highly sensitive to upstream signals and strongly interacted with gain-of-function mutations of upstream factors. They suppressed mutations for receptor tyrosine kinases (RTKs); torso (tor), sevenless (sev) and to a lesser extent Drosophila EGF receptor (DER). Furthermore, the Dsor1 alleles showed no significant interaction with gain-of-function mutations of DER. The observed difference in activity of the Dsor1 alleles among the RTK pathways suggests Dsor1 is one of the components of the pathway that regulates signal specificity. Expression of Dsor1 in budding yeast demonstrated that Dsor1 can activate yeast MAP kinase homologues if a proper activator of Dsor1 is coexpressed. Nucleotide sequencing of the Dsor1 mutant genes revealed that most of the mutations are associated with amino acid changes at highly conserved residues in the kinase domain. The results suggest that they function as suppressors due to increased reactivity to upstream factors.

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Signal-mediated localization of Candida albicans pheromone response pathway components

G3 Genes|Genome|Genetics ◽

10.1093/g3journal/jkaa033 ◽

2020 ◽

Author(s):

Anna Carolina Borges Pereira Costa ◽

Raha Parvizi Omran ◽

Chris Law ◽

Vanessa Dumeaux ◽

Malcolm Whiteway

Keyword(s):

Candida Albicans ◽

Map Kinase ◽

Nuclear Localization ◽

Map Kinases ◽

Critical Role ◽

Cell Periphery ◽

Pheromone Response ◽

Pheromone Response Pathway ◽

Localization Signal ◽

In Cells

Abstract Candida albicans opaque cells release pheromones to stimulate cells of opposite mating type to activate their pheromone response pathway. Although this fungal pathogen shares orthologous proteins involved in the process with Saccharomyces cerevisiae, the pathway in each organism has unique characteristics. We have used GFP-tagged fusion proteins to investigate the localization of the scaffold protein Cst5, as well as the MAP kinases Cek1 and Cek2, during pheromone response in C. albicans. In wild-type cells, pheromone treatment directed Cst5-GFP to surface puncta concentrated at the tips of mating projections. These puncta failed to form in cells defective in either the Gα or β subunits. However, they still formed in response to pheromone in cells missing Ste11, but with the puncta distributed around the cell periphery in the absence of mating projections. These puncta were absent from hst7Δ/Δ cells, but could be detected in the ste11Δ/Δ hst7Δ/Δ double mutant. Cek2-GFP showed a strong nuclear localization late in the response, consistent with a role in adaptation, while Cek1-GFP showed a weaker, but early increase in nuclear localization after pheromone treatment. Activation loop phosphorylation of both Cek1 and Cek2 required the presence of Ste11. In contrast to Cek2-GFP, which showed no localization signal in ste11Δ/Δ cells, Cek1-GFP showed enhanced nuclear localization that was pheromone independent in the ste11Δ/Δ mutant. The results are consistent with CaSte11 facilitating Hst7-mediated MAP kinase phosphorylation and also playing a potentially critical role in both MAP kinase and Cst5 scaffold localization.

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The Cek1 and Hog1 Mitogen-Activated Protein Kinases Play Complementary Roles in Cell Wall Biogenesis and Chlamydospore Formation in the Fungal Pathogen Candida albicans

Eukaryotic Cell ◽

10.1128/ec.5.2.347-358.2006 ◽

2006 ◽

Vol 5 (2) ◽

pp. 347-358 ◽

Cited By ~ 109

Author(s):

B. Eisman ◽

R. Alonso-Monge ◽

E. Román ◽

D. Arana ◽

C. Nombela ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Map Kinase ◽

Fungal Pathogen ◽

Hog Pathway ◽

Cell Wall Biogenesis ◽

Chlamydospore Formation ◽

Mitogen Activated Protein ◽

Morphological Transitions ◽

Relationship Of

ABSTRACT The Hog1 mitogen-activated protein (MAP) kinase mediates an adaptive response to both osmotic and oxidative stress in the fungal pathogen Candida albicans. This protein also participates in two distinct morphogenetic processes, namely the yeast-to-hypha transition (as a repressor) and chlamydospore formation (as an inducer). We show here that repression of filamentous growth occurs both under serum limitation and under other partially inducing conditions, such as low temperature, low pH, or nitrogen starvation. To understand the relationship of the HOG pathway to other MAP kinase cascades that also play a role in morphological transitions, we have constructed and characterized a set of double mutants in which we deleted both the HOG1 gene and other signaling elements (the CST20, CLA4, and HST7 kinases, the CPH1 and EFG1 transcription factors, and the CPP1 protein phosphatase). We also show that Hog1 prevents the yeast-to-hypha switch independent of all the elements analyzed and that the inability of the hog1 mutants to form chlamydospores is suppressed when additional elements of the CEK1 pathway (CST20 or HST7) are altered. Finally, we report that Hog1 represses the activation of the Cek1 MAP kinase under basal conditions and that Cek1 activation correlates with resistance to certain cell wall inhibitors (such as Congo red), demonstrating a role for this pathway in cell wall biogenesis.

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Activation of mitogen-activated protein (MAP) kinase by a MAP kinase-kinase.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)42181-3 ◽

1992 ◽

Vol 267 (19) ◽

pp. 13135-13137 ◽

Cited By ~ 2

Author(s):

P.D. Adams ◽

P.J. Parker

Keyword(s):

Map Kinase ◽

Protein Map ◽

Mitogen Activated Protein ◽

Map Kinase Kinase

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Identification and characterization of a new mammalian mitogen-activated protein kinase kinase, MKK2

Molecular and Cellular Biology ◽

10.1128/mcb.13.8.4539-4548.1993 ◽

1993 ◽

Vol 13 (8) ◽

pp. 4539-4548

Author(s):

J Wu ◽

J K Harrison ◽

P Dent ◽

K R Lynch ◽

M J Weber ◽

...

Keyword(s):

Protein Kinase ◽

Map Kinase ◽

Protein Kinases ◽

Map Kinases ◽

Sodium Dodecyl ◽

Rat Tissues ◽

Tyrosine Residues ◽

Mitogen Activated Protein ◽

Map Kinase Kinase

Mitogen-activated protein (MAP) kinases are serine/threonine protein kinases activated by dual phosphorylation on threonine and tyrosine residues. A MAP kinase kinase (MKK1 or MEK1) has been identified as a dual-specificity protein kinase that is sufficient to phosphorylate MAP kinases p42mapk and p44mapk on the regulatory threonine and tyrosine residues. Because of the multiplicity of MAP kinase isoforms and the diverse circumstances and agonists leading to their activation, we thought it unlikely that a single MKK could accommodate this complexity. Indeed, two protein bands with MKK activity have previously been identified after renaturation following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We now report the molecular cloning and characterization of a second rat MAP kinase kinase cDNA, MKK2. MKK2 cDNA contains an open reading frame encoding a protein of 400 amino acids, 7 residues longer than MKK1 (MEK1). The amino acid sequence of MKK2 is 81% identical to that of MKK1, but nucleotide sequence differences occur throughout the aligned MKK2 and MKK1 cDNAs, indicating that MKK2 is the product of a distinct gene. MKK1 and MKK2 mRNAs are expressed differently in rat tissues. Both cDNAs when expressed in COS cells displayed the ability to phosphorylate and activate p42mapk and p44mapk, both MKK1 and MKK2 were activated in vivo in response to serum, and both could be phosphorylated and activated by the v-Raf protein in vitro. However, differences between MKK1 and MKK2 in sites of phosphorylation by proline-directed protein kinases predict differences in feedback regulation.

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