Effects of Nutrient Depletion in Cell Proliferation and Growth

Tuberous Sclerosis Complex (TSC) is a rare genetic disorder affecting 1 in every 6000 births work wide. The disease is characterized by the formation benign tumors in various tissues such as the kidneys, brain, heart, lungs, skin, and eyes. TS isalso related to other medical conditions such as seizures, intellectual delay, and autism spectrum disorder and can progress to malignant cancers. TSC is caused by mutations in either the TSC1 or TSC2 tumor suppressor genes, also known as Hamartin and Tuberin respectively. The loss of Tuberinexpression has been linked with most severe clinical outcomes and is found in several cancers including those of the breast, lung, ovaries, liver, brain, and urothelia. Our lab has shown that Tuberin binds the cell cycle protein, CyclinB1 at the G2/M checkpoint of the cell cycle. This interaction retains Cyclin B1 in the cytoplasm thereby slowing the onset of mitosis. Under low intracellular ATP conditions an upstream regulator of Tuberin, AMP-activated serine/threonine protein kinase (AMPK), phosphorylates Tuberin creating a downstream signal cascade inhibiting protein synthesis. We hypothesize that lack of nutrients may disrupt the Tuberin-Cyclin B1 complex to support enhanced cell division, thereby allowing tumours to form. For this work I have altered the TSC2 genome to mimic AMPK alterations in the Tuberin protein. I have tested the effects of alteration on binding to Cyclin B1 and on cell growth as compared to the wild-type protein. This work is dissecting the key mechanisms regulating cell growth and division and may reveal ways that tumour cells continue to grow under adverse, unfavourable conditions