RP1: Targeting Beclin 1 complexes for broad-spectrum anti-infective therapeutics

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Project Summary – RP1: The autophagic delivery of intracellular pathogens to the lysosome for destruction is a central mechanism of innate immunity. Our objective is to develop successful strategies to increase autophagy in cells/tissues of patients infected with intracellular pathogens to treat priority pathogens such as chikungunya virus (CHIKV), West Nile virus (WNV), Zika virus (ZIKV) and other infectious diseases. We discovered (1) the first mammalian gene shown to function in autophagy, beclin 1; (2) a conserved role for autophagy genes in antimicrobial host defense; (3) a cell penetrating autophagy-inducing peptide (Tat-Beclin 1) with broad-spectrum anti-infective activity in vivo; and (4) molecular mechanisms that regulate Beclin 1 autophagy activity, including inhibition by Bcl-2 binding. In our current CETR program, we (1) optimized the Tat-Beclin 1 peptide (now moving into IND-enabling studies with our partner Casma Therapeutics); (2) identified nanomolar potency chemical entities that disrupt Bcl-2/Beclin 1 binding and induce autophagy; and (3) used a genome-wide siRNA screen to identify proteins that trigger autophagy during viral infection, leading to the discovery of SNX5 as a newly-identified Beclin 1 binding protein that is important for antiviral immunity. Furthermore, we generated mice with a knock-in Beclin 1 mutation that disrupts Bcl-2 binding and increases basal autophagy; these mice have extended lifespan and healthspan, and show decreased M. tuberculosis replication and susceptibility to lethal CHIKV infection. This provides important genetic proof-of-principle that increased autophagy is safe and validates disruption of Bcl-2/Beclin binding as a target for autophagy-inducing therapeutics. To accomplish our objective, we will leverage discoveries made during our current CETR Program research to (1) advance our current semi-optimized compounds (Tat-Beclin 1, Bcl-2/Beclin 1 binding disruptors), and (2) discover new chemical entities that induce anti-infective autophagy by mimicking the mechanism of action of Tat-Beclin 1, increasing the activity of Beclin 1 Class III phosphatidylinositol 3-kinase (PI3K) autophagy complexes, or enhancing the autophagy-inducing activity of SNX5. This will be accomplished by a multidisciplinary team at UTSW with expertise in high-throughput chemical screening, medicinal chemistry, structural biology, and pre-clinical pharmacology, as well as in collaboration with chemists in other CETR Projects (RP2, RP5). We will evaluate the efficacy of new chemical entities that arise from our new work and other projects in this CETR Program (RP2-RP5) in our established neonatal animal models of WNV, CHIKV, and ZIKV. We anticipate that these approaches (aimed at activating Beclin 1 autophagy function) will result in identification of lead compounds for future IND-enabling studies to develop new autophagy pathway- directed broad-spectrum anti-infectives.