AfRip3, a RIP3-like kinase, is identified as a key modulator of necroptotic death in Aspergillus fumigatus

Abstract

Aspergillus fumigatus exhibits autophagic and necroptotic process when its GPI anchor synthesis is suppressed. A putative kinase (AFUA_6G02590) is found to be overexpressed in response to GPI anchor suppression and identified as a RIP3-like protein, namely AfRip3. To elucidate its function, in this study a Afrip3-overexpressing strain OE-Afrip3 was constructed. Although OE-Afrip3 strain exhibited an increased cell death, neither apoptotic nor autophagic process was activated. Our evidences demonstrated that overexpression of Afrip3 gene in A. fumigatus only led to necroptosis, while the Afrip3-knockout mutant was unable to activate necroptotic process. Further analysis revealed that both JNK and SMase pathways were activated in OE-Afrip3 strain, by which an increase of reactive oxygen species (ROS) was induced. We also showed that expression of Afrip3 gene was induced by Ca2+. In addition, eEF1B{gamma} and adenylylsulfate kinase (ASK) were identified as potential candidates to interact with AfRip3. These results indicate that AfRip3 is a key modulator that activates necroptotic process in A. fumigatus, which can be induced by Ca2+ and in turn activate JNK (c-Jun NH2-terminal kinase) and SMase (sphingomyelinase) pathway. Our findings suggest that necroptotic pathway in A. fumigatus is distinct from that in mammalian cell and may provide a new strategy for development of anti-fungal drug. Author summaryAspergillus fumigatus is a human fungal pathogen and causes invasive aspergillosis (IA) in immunocompromised patients with high mortality (30-95%). Development of novel therapies is urgently needed. In this study, we confirm AfRip3 (AFUA_6G02590), a RIP3-like protein, is a key modulator that activates necroptotic process in A. fumigatus. We also find that cytosolic Ca2+ can induce the expression of Afrip3 and activated AfRip3 in turn activate JNK (c-Jun NH2-terminal kinase) and SMase (sphingomyelinase) pathway. Our findings suggest that necroptotic pathway in A. fumigatus is distinct from that in mammalian cell and may provide a new strategy for development of anti-fungal drug.