Prof John CONNOLLY Research Director Translational Immunology Institute of Molecular and Cell Biology
A novel strategy for single-cell metabolic analysis highlights rapid metabolic reprogramming during immune tolerance induction
Dendritic cells regulate the balance between immunity and tolerance through selective activation by environmental and pathogen derived triggers. In order to characterize the rapid changes which occur during this process, we analysed the underlying metabolic activity across a spectrum of functional DC activation states, from immunogenic to tolerogenic. We found that in contrast to the pronounced proinflammatory program of mature DCs, tolerogenic DCs displayed a markedly augmented catabolic pathway, related to oxidative phosphorylation (OXPHOS), fatty acid oxidation and glycolysis. Functionally, tolerogenic DCs demonstrated the highest mitochondrial oxidative activity, production of reactive oxygen species, superoxide, and increased spare respiratory capacity. Furthermore, assembled, electron transport chain complexes (I-V) were significantly more abundant in tolerogenic DCs. Inhibition of mitochondrial OXPHOS selectively blocked the differentiation of tolerogenic DCs. At the level of glycolysis, tolerogenic and mature DCs showed similar glycolytic rates, but glycolytic capacity and reserve, were more pronounced in tolerogenic DCs. The enhanced reserve glycolytic and respiratory capacity observed in these DCs was reflected in a higher metabolic plasticity to maintain intracellular ATP content. Interestingly, tolerogenic and mature DCs manifested substantially different expression of proteins involved in fatty acid oxidation (FAO) pathway and FAO activity was significantly higher in tolerogenic DCs. Inhibition of FAO prevented the differentiation to tolerogenic DCs demonstrating their dependence on fatty acid as an essential carbon source. Overall, tolerogenic DCs show metabolic signatures of increased and stable OXPHOS programing, a shift in overall redox state and high plasticity for metabolic adaptation. These observations point to a mechanism for rapid, large scale epigenetic reprograming by modulation of underlying cellular metabolism during DC differentiation.
BIO Dr. Connolly is a Research Director and Director for Translational Immunology at the Institute of Molecular and Cellular Biology (IMCB). Additionally, Dr. Connolly serves as Program Director for the A*Star Program in Translational Research in Infectious Disease, a multi-disciplinary center focused on target discovery and vaccine development. As a human immunologist, his research interests focus on target discovery for immune modulation. An Adjunct Associate Professor of Immunology at Baylor University, he serves on the Board of Governors for the Institute of Biomedical Sciences. Dr. Connolly received his Ph.D. in Immunology from Dartmouth Medical School and studied human dendritic cell biology under Dr. Michael Fanger. During this time he was involved in the development of immunotherapeutic preclinical models and clinical trials for Glioblastoma multiforme (GBM). He moved to the Baylor Institute for Immunology Research, a fully translational research institute dedicated to rationally designed vaccines against cancer and infectious disease. Dr. Connolly served as the Director of Research Initiatives for the Baylor Research Institute, leading a large integrated translational research resource and multi-institutional programs that involved a number of international sites. During his tenure at Baylor, Dr. Connolly was the central core facility director of the NIAID Centers for Translational Research on Human Immunology and Biodefense, an NIH funded consortium of basic, translational research and clinical trials focused on vaccine design. Dr. Connolly is the past President of the Board of Directors of The American Cancer Society in N. Texas and founding Director of the Singapore Immunology Network’s Immunomonitoring Platform.