The
 pkaB
 Gene Encoding the Secondary Protein Kinase A Catalytic Subunit Has a Synthetic Lethal Interaction with
 pkaA
 and Plays Overlapping and Opposite Roles in
 Aspergillus nidulans

Ni, Min; Rierson, Sara; Seo, Jeong‐Ah; Yu, Jae‐Hyuk

doi:10.1128/ec.4.8.1465-1476.2005

Cited by 57 publications

(72 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The same was observed for an A. nidulans PKAdeficient mutant. In contrast, conidia of a mutant overexpressing pkaB, encoding a putative second catalytic subunit of PKA of A. nidulans with minor importance, were not able to germinate (21). For a pkaR deletion mutant of A. fumigatus, retarded spore germination and a severe reduction of spore viability were reported (34).…”

Section: Discussionmentioning

confidence: 99%

Protein Kinase A Regulates Growth, Sporulation, and Pigment Formation in Aspergillus fumigatus

Grosse

Heinekamp

Kniemeyer

et al. 2008

Appl Environ Microbiol

View full text Add to dashboard Cite

Aspergillus fumigatus is an opportunistic human pathogenic fungus causing severe infections in immunocompromised patients. Cyclic AMP (cAMP) signal transduction plays an important role in virulence. A central component of this signaling cascade is protein kinase A (PKA), which regulates cellular processes by phosphorylation of specific target proteins. Here we describe the generation and analysis of A. fumigatus mutants expressing the gene encoding the catalytic subunit of PKA, pkaC1, under control of an inducible promoter. Strains overexpressing pkaC1 showed high PKA activity, reduced growth, sporulation deficiency, and formation of a dark pigment in the mycelium. These data indicate that cAMP-PKA signaling is involved in the regulation of important processes, such as growth, asexual reproduction, and biosynthesis of secondary metabolites. Furthermore, elevated PKA activity led to increased expression of the pksP gene. The polyketide synthase PksP is an essential enzyme for production of dihydroxynaphthalene-melanin in A. fumigatus and contributes to virulence. Our results suggest that increased pksP expression is responsible for pigment formation in the mycelium. Comparative proteome analysis of the pkaC1-overexpressing strain and the wild-type strain led to the identification of proteins regulated by the cAMP-PKA signal transduction pathway. We showed that elevated PKA activity resulted in activation of stress-associated proteins and of enzymes involved in protein biosynthesis and glucose catabolism. In contrast, proteins which were involved in nucleotide and amino acid biosynthesis were downregulated, as were enzymes involved in catabolism of carbon sources other than glucose.

show abstract

Section: Discussionmentioning

confidence: 99%

Protein Kinase A Regulates Growth, Sporulation, and Pigment Formation in Aspergillus fumigatus

Grosse

Heinekamp

Kniemeyer

et al. 2008

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…In A. nidulans, conidial germination occurs in the presence of a carbon source alone (21,24). We examined germination in A. oryzae and observed that conidial germination of the wild type was induced on CD medium lacking a nitrogen source (CDϪN).…”

Section: Discussionmentioning

confidence: 99%

Functional Analysis of the ATG8 Homologue Ao atg8 and Role of Autophagy in Differentiation and Germination in Aspergillus oryzae

et al. 2006

View full text Add to dashboard Cite

Autophagy is a well-known degradation system, induced by nutrient starvation, in which cytoplasmic components and organelles are digested via vacuoles/lysosomes. Recently, it was reported that autophagy is involved in the turnover of cellular components, development, differentiation, immune responses, protection against pathogens, and cell death. In this study, we isolated the ATG8 gene homologue Aoatg8 from the filamentous fungus Aspergillus oryzae and visualized autophagy by the expression of DsRed2-AoAtg8 and enhanced green fluorescent protein-AoAtg8 fusion proteins in this fungus. While the fusion proteins were localized in dot structures which are preautophagosomal structure-like structures under normal growth conditions, starvation or rapamycin treatment caused their accumulation in vacuoles. DsRed2 expressed in the cytoplasm was also taken up into vacuoles under starvation conditions or during the differentiation of conidiophores and conidial germination. Deletion mutants of Aoatg8 did not form aerial hyphae and conidia, and DsRed2 was not localized in vacuoles under starvation conditions, indicating that Aoatg8 is essential for autophagy. Furthermore, Aoatg8 conditional mutants showed delayed conidial germination in the absence of nitrogen sources. These results suggest that autophagy functions in both the differentiation of aerial hyphae and in conidial germination in A. oryzae.Autophagy is a protein degradation system that is conserved in eukaryotic cells and used to recycle macromolecules and aid cell survival under nutritional starvation conditions (12, 13). When autophagy is induced, bulk cytoplasm and/or organelles are sequestered within double-membrane vesicles termed autophagosomes. The outer membranes of the autophagosomes then fuse to the vacuolar/lysosomal membrane and deliver single-membrane vesicles, called autophagic bodies, into the lumina of the vacuoles/lysosomes. The subsequent breakdown of the vesicle membranes allows the degradation of the contents of the autophagic bodies by vacuolar hydrolases. ATG8 is an autophagy-related gene found in Saccharomyces cerevisiae that plays an important role in the formation of autophagosomes (9). Atg8 is localized in the membranes of preautophagosomal structures (PAS), autophagosomes, and autophagic bodies and has therefore been used as a marker of these organelles (33).In addition to helping cells to survive starvation, autophagy is involved in stress-induced differentiation and development. In S. cerevisiae diploid cells, atg mutations block starvationinduced sporulation (34). In Dictyostelium discoideum, starvation, overcrowding, and high temperature induce the formation of fruiting bodies and atg mutations block these multicellular developmental processes (25). Additionally, in Caenorhabditis elegans, atg mutations result in abnormal dauer development, which is also induced by starvation, overcrowding, high temperature and so on (17). Recent studies have suggested that autophagy might participate in diseases such as cancer, liver disease, muscula...

show abstract

“…Deletion of one or more catalytic subunits in each of these fungi has been shown to decrease growth, to reduce the tolerance to oxidative stress, and, in A. fumigatus, to reduce virulence, perhaps by modulation of the expression of polyketide synthase (18,20). Interestingly, in A. nidulans, deletion of pkaA, one of the catalytic subunits, or overexpression of pkaB, the second catalytic subunit, leads to increased sensitivity to oxidative stress (27). We have previously shown with A. fumigatus that transcripts for the regulatory subunit of PKA, pkaR, are up-regulated when the fungus is grown in the presence of endothelial cells or pulmonary epithelial cells (29,36).…”

mentioning

confidence: 99%

“…Indeed, mutants of serotype A that lack the regulatory subunit of PKA overproduce capsule and are hypervirulent, whereas those same mutants in serotype D have wild-type (WT) virulence (16). In the plant pathogen Ustilago maydis, deletion of the regulatory subunit of PKA leads to a multiple-budding phenotype and the inability to form galls in colonized plants, which was reflected in reduced disease scores (14).Within the genus Aspergillus, analysis of PKA signaling has been limited to Aspergillus niger, Aspergillus nidulans, and Aspergillus fumigatus (2,21,27,40). Deletion of one or more catalytic subunits in each of these fungi has been shown to decrease growth, to reduce the tolerance to oxidative stress, and, in A. fumigatus, to reduce virulence, perhaps by modulation of the expression of polyketide synthase (18,20).…”

mentioning

confidence: 99%

“…Within the genus Aspergillus, analysis of PKA signaling has been limited to Aspergillus niger, Aspergillus nidulans, and Aspergillus fumigatus (2,21,27,40). Deletion of one or more catalytic subunits in each of these fungi has been shown to decrease growth, to reduce the tolerance to oxidative stress, and, in A. fumigatus, to reduce virulence, perhaps by modulation of the expression of polyketide synthase (18,20).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Deletion of the Regulatory Subunit of Protein Kinase A in Aspergillus fumigatus Alters Morphology, Sensitivity to Oxidative Damage, andVirulence

et al. 2006

View full text Add to dashboard Cite

Aspergillus fumigatus is an important opportunistic fungal pathogen. The cAMP-dependent protein kinase (PKA) signaling pathway plays an important role in regulating morphology, growth, and virulence in a number of fungal pathogens of plants and animals. We have constructed a mutant of A. fumigatus that lacks the regulatory subunit of PKA, pkaR, and analyzed the growth and development, sensitivity to oxidative damage, and virulence of the mutant, along with those of the wild type and a complemented mutant. Both growth and germination rates of the mutant are reduced, and there are morphological abnormalities in conidiophores, leading to reduced conidiation. Conidia from the ⌬pkaR mutant are more sensitive to killing by hydrogen peroxide, menadione, paraquat, and diamide. However, the hyphae of the mutant are killed to a greater extent only by paraquat and diamide, whereas they are less susceptible to the effects of hydrogen peroxide. In an immunosuppressed mouse model, intranasally administered conidia of the mutant are significantly less virulent than those of the wild type or a complemented mutant. Unregulated PKA signaling is detrimental to the virulence of A. fumigatus, perhaps through the reduced susceptibility of the mutant to damage by oxidizing agents and reduced growth kinetics.Aspergillus fumigatus is an important fungal pathogen of immunocompromised hosts (23,34). Despite the recent introduction of newer antifungals with anti-Aspergillus activity, the morbidity and mortality of invasive aspergillosis (IA) remains high, especially once the infection has disseminated (7). In nature, the fungus plays a key role in the compost cycle by recycling carbon and nitrogen from plant material (24, 42). In this environment, A. fumigatus is likely to be exposed to broad fluctuations in pH, temperatures up to 50°C, and reactive oxygen species (24,33,45). These stressors are not unlike the kinds of factors an organism might encounter in vivo (13). Therefore, adaptive mechanisms that confer resistance to environmental stress may contribute to the efficient colonization and persistence of the organism in the human host.The cyclic AMP-dependent protein kinase (PKA) is a wellknown regulator of the stress response in eukaryotes. PKA is a heterotetramer, made up of a dimer of regulatory subunits and two catalytic subunits. Fungal regulatory subunits are homologues of mammalian type II subunits, based on the autoinhibition site (29). When cAMP binds to the regulatory subunits, a conformational change occurs, which releases the catalytic subunits to autophosphorylate and to phosphorylate downstream targets. PKA signaling in Saccharomyces cerevisiae regulates the general stress control pathway (11,26). Mutants lacking BCY1, the gene encoding the regulatory subunit of PKA in S. cerevisiae, have unregulated PKA activity; these mutants are pseudohyphal in morphology and hypersensitive to killing with hydrogen peroxide (15, 44).The PKA pathway also regulates morphology and virulence in a number of fungal pathogens of humans and pla...

show abstract

The pkaB Gene Encoding the Secondary Protein Kinase A Catalytic Subunit Has a Synthetic Lethal Interaction with pkaA and Plays Overlapping and Opposite Roles in Aspergillus nidulans

Cited by 57 publications

References 49 publications

Protein Kinase A Regulates Growth, Sporulation, and Pigment Formation in Aspergillus fumigatus

Protein Kinase A Regulates Growth, Sporulation, and Pigment Formation in Aspergillus fumigatus

Functional Analysis of the ATG8 Homologue Ao atg8 and Role of Autophagy in Differentiation and Germination in Aspergillus oryzae

Deletion of the Regulatory Subunit of Protein Kinase A in Aspergillus fumigatus Alters Morphology, Sensitivity to Oxidative Damage, andVirulence

Contact Info

Product

Resources

About