Abstract
The susceptibility of CD4 T cells to HIV-1 infection is regulated by glucose and glutamine metabolism, but the relative contributions of these nutrients to infection are not known. During my PhD, I identified glutaminolysis as a major pathway fueling oxidative phosphorylation (OXPHOS) in activated naïve as well as memory CD4 cell subsets, and found that induction of this metabolic network is required for optimal HIV-1 infection. Moreover, we determined that under conditions of attenuated glutaminolysis, the α-ketoglutarate (αKG) TCA (tricarboxylic acid) cycle intermediate is a rate-limiting step in infection; exogenous α-KG directly increased OXPHOS and rendered both naïve and memory CD4 T cells significantly more sensitive to infection. Furthermore, blocking the glycolytic flux of pyruvate to lactate resulted in an increased OXPHOS and a significantly augmented level of HIV-1 infection. In agreement with these data, infected CD4 T cells exhibited increased mitochondrial biomass and respiration as compared to their non-infected counterparts. These data identify the OXPHOS/ aerobic glycolysis balance as a major regulator of HIV-1 infection in CD4 T lymphocytes.In order to gain more insight into the metabolic pathways regulating HIV-1 infection in CD4 T cells, we developed a complementary approach to target upstream processes, specifically altering glucose (GLUT1), glutamine (ASCT2), and arginine (CAT1) transporter expression by lentiviral-mediated delivery of specific shRNAs. Testifying to the importance of these transporters, CD4 T cells with downregulated expression of either GLUT1, ASCT2 or CAT1 were negatively selected, resulting in a loss of approximately 80% of shRNA-transduced cells within 14 days. Notably, the permissivity of CD4 T cells to HIV-1 infection was differentially impacted by inhibition of specific nutrient transporters. Consistent with the data presented above, knockdown of GLUT1 did not significantly impact HIV-1 infection whereas knockdown of CAT1 significantly decreased both OXPHOS as well as HIV-1 infection (by 35%). Surprisingly though, ASCT2 knockdown resulted in a significantly augmented infection, by approximately 20%. Mechanistically, we found that this was associated with a markedly higher persistence of naïve, as compared to memory, T cells with downregulated ASCT2 levels. These data highlight differences in the relative importance of distinct nutrient transporters in the survival of naïve vs memory CD4 T cell subsets and demonstrate their specific impact on the sensitivity of these populations to HIV-1 infection.In conclusion, using two complementary approaches, my PhD research has revealed the critical impact of a CD4 T cell’s energetic state on its susceptibility to HIV-1 infection. My data identify the importance of mitochondrial metabolism, with an environment rich in TCA cycle intermediates such as α-KG, in regulating the susceptibility of CD4 T cells to HIV-1 infection. Furthermore, I find that nutrient transporter expression differentially impacts the sensitivity of naïve and memory CD4 T cells to HIV-1 infection. These studies therefore provide new prospects for the development of targeted metabolic therapeutic strategies against HIV-1 infection.