Inhibition of protein kinase A affects Paracoccidioides lutzii dimorphism

Abstract

A critical step in the lifecycle of many fungal pathogens is the ability to switch between filamentous and yeast growth, a process known as dimorphism. cAMP-dependent protein kinase (PKA) controls morphological changes and the pathogenicity of several animal and plant pathogenic fungi. In this work, we report the analysis of PKA activity during the mycelium to yeast transition in the pathogenic fungus Paracoccidioides lutzii. This fungus, as well as the closely related species Paracoccidioides brasiliensis, causes paracoccidioidomycosis, a systemic mycosis that affects thousands of people in Latin America. Infection occurs when hypha fragments or spores released from mycelium are inhaled by the host, an event that triggers the morphological switch. We show here that PKA activity is regulated in the fungus phase, increasing during the mycelium to yeast transition. Also, morphological transition from mycelium to yeast is blocked by the compound H89, a specific PKA inhibitor. Nevertheless, the fungus recovers its ability to change morphology when H89 is removed from the culture media. This recovery is accompanied by a significant increase in PKA activity. Our results strongly indicate that PKA directly affects phase transition in P. lutzii.

Updates in Paracoccidioides Biology and Genetic Advances in Fungus Manipulation

“…It is known that in several pathogenic fungi, the cAMP/PKA pathway controls morphology and pathogenicity and that organisms can respond quickly to environmental changes through this pathway. A study performed in P. lutzii demonstrated that when PKA activity is inhibited, the transition from mycelium to yeast is compromised [54]. Additionally, there is an increase in cyclic adenosine 3 ,5 monophosphate (cAMP) in the process of dimorphic transition in P. brasiliensis [55].…”

Aspergillus fumigatus Can Display Persistence to the Fungicidal Drug Voriconazole

“…In C. albicans , fluconazole tolerance (but not resistance) can be prevented with the use of adjuvant drugs that block general stress signaling pathways ( 35 ). To further investigate whether the underlying mechanism of persistence may be different in A. fumigatus , we tested the effect of various drug adjuvants that were previously shown to eliminate tolerance in C. albicans ( 35 ): geldanamycin (0.8 μg/mL), an inhibitor of heat shock protein (Hsp90) ( 63 , 64 ); FK506 (4 ng/mL), an inhibitor of calcineurin ( 65 ); H-89 (4 μg/mL), an inhibitor of the cAMP-dependent protein kinase A ( 66 ); rapamycin (6.25 μg/mL), an inhibitor of the mammalian target of rapamycin (mTOR) ( 67 ); and tunicamycin (10 μg/mL), an inducer of the unfolded protein response pathway ( 68 ). In contrast to C. albicans , the use of adjuvant drugs did not prevent persistence of A. fumigatus isolates ( Fig.…”

Aspergillus fumigatuscan display persistence to the fungicidal drug voriconazole

“…In C. albicans , fluconazole tolerance (but not resistance) can be prevented with the use of adjuvant drugs that block general stress signalling pathways [21]. To further investigate if the underlying mechanism of persistence may be different in A. fumigatus , we tested the effect of various drug adjuvants that were previously shown to eliminate tolerance in C. albicans [21]: geldanamycin (0.8 µg/mL), an inhibitor of heat shock protein (Hsp90) [49, 50], FK506 (4 ng/mL), an inhibitor of calcineurin [51], H-89 (4 µg/mL), an inhibitor of the cAMP-dependent protein kinase (PKA) [52], rapamycin (6.25 µg/mL), an inhibitor of the mammalian target of rapamycin (mTOR) [53], and tunicamycin (10 µg/mL), an inducer of the unfolded protein response pathway [54]. In contrast to C. albicans , the use of adjuvant drugs did not prevent persistence of A. fumigatus isolates (Fig.…”