Compromised autophagy allows Burkholderia cenocepacia persistence in macrophages derived from cystic fibrosis patients

• Applicant: Dr. Kathrin Krause
• Subject Area: Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264645464

Among patients with cystic fibrosis (CF) an infection with Burkholderia cenocepacia represents a substantial risk associated with reduced survival. Once infected, CF patients succumb to chronic destructive lung inflammation and severe sepsis (cepacia syndrome). Murine macrophages clear B. cenocepacia infection through autophagy. Within murine CF macrophages mutant Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein aggregates sequester essential autophagy molecules limiting their availability for the formation of autophagosomes when needed. However, murine CF macrophages express higher levels of p62 when compared to non-CF cells. P62 is an adaptor molecule that targets autophagy cargo to autophagosomes and has the tendency to self aggregate. Preliminary work showed that down-regulation of p62 with specific siRNA in murine CF macrophages liberated autophagy molecules from the mutant CFTR protein aggregates, thereby making them available for capturing the bacterium within autophagosomes. As a result B. cenocepacia was delivered to the lysosome for degradation and the infection was contained. It could be demonstrated that human CF macrophages also fail to control B. cenocepacia infection, but whether this is due to defective autophagy remains to be elucidated. In addition, absent autophagy has been shown to increase IL-1beta production in response to bacterial agents and autophagosome recruitment can be inhibited by caspase-1 activity. Therefore this proposal aims to determine if compromised autophagy in human CF macrophages contributes to B. cenocepacia persistence and processing of caspase-1, and whether the restoration of autophagy by down-regulation of p62 has the ability to limit inflammation. Data obtained from this study will provide pre-clinical evidence for the validity of p62 as a novel target for clearing B. cenocepacia infection in CF patients.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professorin Amal Amer, Ph.D.