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Cross talk between the cell wall integrity and cyclic AMP/protein kinase A pathways in Cryptococcus neoformans
Maureen J Donlin, Rajendra Upadhya1, Kimberly J Gerik1
1Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Mbio
|August 14, 2014
Summary
The cell wall integrity pathway in Cryptococcus neoformans impacts capsule formation by regulating cyclic AMP (cAMP) levels. Restoring cAMP levels in kinase deletion mutants improves cell wall integrity and capsule production.
Area of Science:
- Mycology
- Cell Biology
- Biochemistry
Background:
- Cryptococcus neoformans causes fatal meningitis in immunocompromised individuals.
- The fungal cell wall is crucial for C. neoformans survival and pathogenesis.
- The cell wall integrity (CWI) signaling pathway regulates cell wall biosynthesis and repair.
Purpose of the Study:
- To investigate the global transcriptional responses to the deletion of BCK1, MKK2, and MPK1 genes in the CWI pathway.
- To explore the relationship between the CWI pathway, cyclic AMP (cAMP)/protein kinase A (PKA) pathway, and fungal capsule production.
- To determine the impact of CWI pathway kinases on cell wall integrity and capsule homeostasis.
Main Methods:
- Gene deletion of BCK1, MKK2, and MPK1 in C. neoformans.
- Global transcriptional profiling (RNA-Seq) of deletion strains compared to wild-type.
- Biochemical measurement of intracellular cAMP levels.
- Assessment of capsule size and shedding under capsule-inducing conditions.
- Complementation studies with exogenous cAMP addition.
Main Results:
- Over 1,000 genes were differentially expressed in the deletion strains, with 115 common to all three.
- Many differentially expressed genes are known targets of the cAMP/PKA pathway.
- Kinase deletion strains exhibited significantly reduced intracellular cAMP levels.
- Deletion strains produced smaller surface capsules but shed similar amounts compared to wild-type.
- Exogenous cAMP addition rescued cell wall defects and restored capsule size.
Conclusions:
- Direct evidence of cross-talk between the CWI and cAMP/PKA pathways in C. neoformans.
- The CWI pathway plays a role in regulating capsule formation, likely mediated by cAMP levels.
- Understanding this cross-talk is important for regulating cell wall and capsule homeostasis in C. neoformans.
- This interaction has implications for C. neoformans pathogenesis and potential therapeutic strategies.
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