Increasing evidence is showing cells use organelle contact sites to transport lipids, which is an essential process to maintain cellular lipid homeostasis for human health. Indeed, the genes mediating formation of organelle contact sites have been linked to type II diabetes, neurodegenerative diseases, and cancer. Lysosomes play a critical role in processing and transporting lipids derived from different processes, such as autophagy. Autophagy maintains the basal level of lipid metabolites in response to environmental nutrient status, in which lysosomes not only process and deliver lipids but also regulate autophagy by controlling mTORC1, the master of cell growth and metabolism. However, the molecules constructing lysosome-organelle contact sites and the commanding signals regulating the contact dynamics are still largely unknown. Cancer cells have abnormal nutrient environments, exhibit different lysosome dynamics, and hijack autophagy to reprogram lipid metabolism, so it is very important to understand the role of lysosome dynamics in signaling and autophagy and identify the key molecules, which could serve as potential targets for anticancer purpose. The main objectives of this application are to study how lysosome change their dynamics (motility, positioning, and contacts) to function in signaling and lipid trafficking in response to excess environmental lipids in the context of obesity-related cancer. The central hypothesis is that during cancer development, altered nutrient environment changes lysosome dynamics and consequently alters lipid metabolism through mTORC1 and autophagy, which serves as an adaptive way to provide lipids and energy for cancer cells. Our recent discovery of the protein complex BORC and other components of the lysosome-dynamics machinery provides unprecedented opportunities to examine their roles in lipid metabolism. My preliminary results indicate deletion of BORC suppressed tumor growth and at cell level caused cholesterol accumulation in lysosomes and reduced lipid droplets. Further analysis revealed BORC-regulated HOPS complex interacted with ER complex NRZ, which is probably responsible for the formation of lysosome-ER contacts to transport cholesterol from lysosomes to ER. I will continue these studies to uncover how the regulation of lipid transport and signaling by lysosome dynamics promotes cancer cell malignancy and look for the potential anticancer targets for drug development.
The relative ability of cell autonomous HIV-1 restriction factors to interfere with the viral life cycle contributes to a host’s level of susceptibility to infection. Pharmacological enhancement of restriction factor efficacy would be a novel approach to treating HIV infection. However, the mechanistic basis for HIV blockage by restriction factors is not completely understood hampering efforts to employ restriction factor-based host directed therapies. The tripartite motif (TRIM) family of proteins consists of more than 70 members in humans, several of which have been identified as antiviral restriction factors. In this role, TRIMs can diminish viral replication directly by interfering with the viral life cycle or indirectly by fine tuning cellular innate immune responses. TRIM family member TRIM5α accomplishes both of these: first, it prevents retroviral infection of cells by a hitherto unexplained mechanism. Second, TRIM5α also acts as a pattern recognition receptor, promoting the establishment of an antiviral cellular state via the activation of inflammatory signaling pathways upon retroviral recognition. Although TRIMs appear to employ multiple approaches in antiretroviral defense, one strikingly common feature among the TRIM family is that many if not all TRIMs are involved in the regulation and execution of autophagy. In addition to its role as a known defense mechanism against intracellular pathogens (including HIV-1), autophagy is also increasingly recognized as a means of reducing or fine tuning inflammation. Here, we propose to test the hypothesis that autophagy underlies TRIM action in protecting cells against HIV-1 infection and in modulating the TRIM-dependent inflammatory signaling. The studies proposed here have several overarching goals. First, they seek to improve our understanding of the molecular mechanism whereby rhesus TRIM5α both regulates autophagy and directs the autophagic degradation of incoming HIV-1 capsids (Aim 1). Second, they will determine if modulations of the autophagy pathway affect TRIM5α-dependent activation of pro-inflammatory signaling upon lentiviral infection. Finally, they will address whether human TRIMs other than TRIM5α that restrict HIV also employ autophagy in their antiviral actions (Aim 2). We have assembled a team of autophagy and HIV experts to address these questions. Our studies have the potential to uncover the mode of action of several known antiretroviral proteins and lay the groundwork for our understanding of how TRIMs as a family can both positively and negatively affect inflammation. We expect these studies to show that autophagy is a unifying aspect of diverse TRIM actions in HIV defense. Since autophagy can be pharmacologically manipulated, our findings may indicate that modulations of autophagy could be a therapeutic approach to dealing with TRIM-related diseases including HIV/AIDS. Our expertise in TRIMs and autophagy, along with the financial and institutional support to be provided should the COBRE application be funded will ensure successful completion of these aims.