PKA-mediated Autophagy in Aspergillus fumigates

Autophagy is a ubiquitous, non-selective degradation process in eukaryotic cells that is conserved from yeast to man. Autophagy research has increased significantly in the last ten years, as autophagy has been connected with cancer, neurodegenerative disease and various human developmental processes. Autophagy also appears to play an important role in filamentous fungi, impacting growth, morphology and development. In this review, an autophagy model developed for the Aspergillus fumigatus is used as an intellectual framework to discuss autophagy in filamentous fungi. Studies imply that, similar to yeast, fungal autophagy is characterized by the presence of autophagosomes and controlled by the target of rapamycin (Tor) kinase. Autophagy is highly regulated and is under the control of a number of signaling pathways, including the Tor pathway, which coordinates cell growth with nutrient availability. The data shows that autophagy in A.fumigatus is also controlled by the cAMP-dependent protein kinase (PKA) pathway. Elevated levels of PKA activity inhibited autophagy and inactivation of the PKA pathway is sufficient to induce a robust autophagy response. In addition, fungal autophagy is apparently involved in protection against cell death and has significant effects on cellular growth and development. However, the only two putative autophagy proteins characterized in filamentous fungi are Atg1 and Atg8. Here we will discuss various strategies used to study and monitor fungal autophagy as well as the possible relationship between autophagy, physiology, and morphological development.