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A second component of the SltA-dependent cation tolerance pathway in Aspergillus nidulans.

Mellado L, Calcagno-Pizarelli AM, Lockington RA, Cortese MS, Kelly JM, Arst HN, Espeso EA - Fungal Genet. Biol. (2015)

Bottom Line: This functional relationship is reinforced by the fact that numerous mutations in both slt loci can be isolated as suppressors of poor colonial growth resulting from certain vps (vacuolar protein sorting) mutations.Finally, it is noteworthy that SltA and SltB have a similar, limited phylogenetic distribution, being restricted to the pezizomycotina subphylum.The relevance of the Slt regulatory pathway to cell structure, intracellular trafficking and cation homeostasis and its restricted phylogenetic distribution makes this pathway of general interest for future investigation and as a source of targets for antifungal drugs.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biología Celular y Molecular, Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu, 9, 28040 Madrid, Spain.

No MeSH data available.


Related in: MedlinePlus

Working model of the slt regulatory pathway. The SltA transcription factor alternates between two forms, one active and the other inactive. The SltB protein is a signaling element that mediates conversion of SltA into an active regulator of transcription. Among the genes under the control of SltA are those involved in tolerance to cation stress and alkalinity. SltA has a dual activity (Findon et al., 2010; Spielvogel et al., 2008), acting negatively in the transcription of vcxA (a vacuolar cation exchanger coding gene) and acting positively in the expression of enaA (a sodium transporter). SltA is also required for the expression of sltB and probably is involved in its own transcriptional regulation, in both cases through binding to UAS sequences in the promoter.
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f0040: Working model of the slt regulatory pathway. The SltA transcription factor alternates between two forms, one active and the other inactive. The SltB protein is a signaling element that mediates conversion of SltA into an active regulator of transcription. Among the genes under the control of SltA are those involved in tolerance to cation stress and alkalinity. SltA has a dual activity (Findon et al., 2010; Spielvogel et al., 2008), acting negatively in the transcription of vcxA (a vacuolar cation exchanger coding gene) and acting positively in the expression of enaA (a sodium transporter). SltA is also required for the expression of sltB and probably is involved in its own transcriptional regulation, in both cases through binding to UAS sequences in the promoter.

Mentions: In A. nidulans tolerance to elevated concentrations of monovalent and divalent cations requires the activities of, at least, two zinc-finger transcription factors, CrzA and SltA (Spielvogel et al., 2008). Although elements required for signaling to and activation of CrzA and its homologues are well known (see Hernández-Ortiz and Espeso (2013) and references therein), the SltA signaling pathway was previously unknown. Here we identify and characterize a novel second component of the SltA cation stress responsive pathway. The autocalled locus AN6132 encodes SltB, a 1272 aa protein. Absence of SltB activity results in similar phenotypes to those displayed by the lack of SltA function. Sensitivity to elevated extracellular concentration of alkali metal cations lithium, sodium and potassium and divalent alkaline earth metal cation magnesium is a feature of sltBΔ strains. As described for the sltA mutant, calcium is not toxic to sltBΔ strains. Not only does calcium improve growth of sltBΔ strains but, as with sltAΔ, calcium auxotrophy results in double mutants also lacking the HalA kinase. Thus, a clear functional relationship is proposed for SltA and SltB. Predicted functional domains in SltB define this protein as a signaling element for SltA (Fig. 8).


A second component of the SltA-dependent cation tolerance pathway in Aspergillus nidulans.

Mellado L, Calcagno-Pizarelli AM, Lockington RA, Cortese MS, Kelly JM, Arst HN, Espeso EA - Fungal Genet. Biol. (2015)

Working model of the slt regulatory pathway. The SltA transcription factor alternates between two forms, one active and the other inactive. The SltB protein is a signaling element that mediates conversion of SltA into an active regulator of transcription. Among the genes under the control of SltA are those involved in tolerance to cation stress and alkalinity. SltA has a dual activity (Findon et al., 2010; Spielvogel et al., 2008), acting negatively in the transcription of vcxA (a vacuolar cation exchanger coding gene) and acting positively in the expression of enaA (a sodium transporter). SltA is also required for the expression of sltB and probably is involved in its own transcriptional regulation, in both cases through binding to UAS sequences in the promoter.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557415&req=5

f0040: Working model of the slt regulatory pathway. The SltA transcription factor alternates between two forms, one active and the other inactive. The SltB protein is a signaling element that mediates conversion of SltA into an active regulator of transcription. Among the genes under the control of SltA are those involved in tolerance to cation stress and alkalinity. SltA has a dual activity (Findon et al., 2010; Spielvogel et al., 2008), acting negatively in the transcription of vcxA (a vacuolar cation exchanger coding gene) and acting positively in the expression of enaA (a sodium transporter). SltA is also required for the expression of sltB and probably is involved in its own transcriptional regulation, in both cases through binding to UAS sequences in the promoter.
Mentions: In A. nidulans tolerance to elevated concentrations of monovalent and divalent cations requires the activities of, at least, two zinc-finger transcription factors, CrzA and SltA (Spielvogel et al., 2008). Although elements required for signaling to and activation of CrzA and its homologues are well known (see Hernández-Ortiz and Espeso (2013) and references therein), the SltA signaling pathway was previously unknown. Here we identify and characterize a novel second component of the SltA cation stress responsive pathway. The autocalled locus AN6132 encodes SltB, a 1272 aa protein. Absence of SltB activity results in similar phenotypes to those displayed by the lack of SltA function. Sensitivity to elevated extracellular concentration of alkali metal cations lithium, sodium and potassium and divalent alkaline earth metal cation magnesium is a feature of sltBΔ strains. As described for the sltA mutant, calcium is not toxic to sltBΔ strains. Not only does calcium improve growth of sltBΔ strains but, as with sltAΔ, calcium auxotrophy results in double mutants also lacking the HalA kinase. Thus, a clear functional relationship is proposed for SltA and SltB. Predicted functional domains in SltB define this protein as a signaling element for SltA (Fig. 8).

Bottom Line: This functional relationship is reinforced by the fact that numerous mutations in both slt loci can be isolated as suppressors of poor colonial growth resulting from certain vps (vacuolar protein sorting) mutations.Finally, it is noteworthy that SltA and SltB have a similar, limited phylogenetic distribution, being restricted to the pezizomycotina subphylum.The relevance of the Slt regulatory pathway to cell structure, intracellular trafficking and cation homeostasis and its restricted phylogenetic distribution makes this pathway of general interest for future investigation and as a source of targets for antifungal drugs.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biología Celular y Molecular, Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu, 9, 28040 Madrid, Spain.

No MeSH data available.


Related in: MedlinePlus