TSC patients develop multi-system disease including benign tumors of the brain, heart, skin and kidney. By age 10, 80% of children with TSC have renal angiomyolipomas and/or renal cysts. Mammalian target of rapamycin (mTOR) complex 1 (TORC1), which is activated in tuberous sclerosis complex (TSC), is a master regulator of cell growth, cellular metabolism, and autophagy. Treatment with TORC1 inhibitors partially decreases the size of TSC-associated brain and kidney lesions, but they regrow when treatment is stopped. Our central hypothesis is that dysregulation of autophagy and cellular metabolism plays a critical role in the pathogenesis of TSC and in the response of TSC-associated renal lesions to TORC1-targeted therapy.
In Aims 1 and 2, we will test the hypothesis that low levels of autophagy in TSC2-deficient cells lead to a metabolic starvation phenotype, making TSC2-deficient cells hypersensitive to further autophagy inhibition. Consistent with this hypothesis, we have found that inhibiting autophagy induces metabolic dysregulation and decreases the in vivo growth of TSC2-deficient cells.
In Aim 3, we will address the hypothesis that p62/sequestosome1-dependent signaling networks promote the growth and survival of TSC2-deficient cells. Consistent with this hypothesis, we have found that p62 accumulates in human angiomyolipomas and other TSC2-deficient cells as a consequence of low autophagy, and that shRNA down regulation of p62 inhibits the in vivo growth of TSC2-deficient cells. Our in vivo strategy (Aims 2 and 3) includes TSC2-deficient angiomyolipoma-derived cells and renal cyst/cystadenoma quantitation in Tsc2+/- mice. Throughout the proposal, we will utilize innovative, state-of-the-art technology including real-time monitoring of bioenergetic parameters using the Seahorse system, metabolomic profiling in collaboration with the Broad Institute, high throughput synthetic-lethality drug screening, and in vivo bioluminescent detection of angiomyolipoma cells. Novel reagents will be generated, including 2 new mouse models (Tsc2+/-Atg5+/- and Tsc2+/-p62-/-.) and angiomyolipoma-derived cells with shRNA down regulation of key molecules. The significance of this project is that it will reveal for the firsttime how autophagy-dependent cellular networks contribute to the pathogenesis of renal disease in TSC. We expect this project to have high impact because TSC-associated lesions have devastating consequences in both children and adults and because the TORC1 signaling network is dysregulated in other human diseases including polycystic kidney disease.
Novel therapeutic paradigms are urgently needed for children and adults with TSC, for whom the only non- surgical treatment option is continuous, perhaps life-long, treatment with TORC1 inhibitors. We will identify the central mechanisms through which autophagy-dependent signaling networks impact the pathogenesis and targeted therapy of TSC, leading to new therapeutic paradigms for TSC and the many other human diseases in which the TORC1 signaling axis is dysregulated.
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