Investigation of the Function and Regulatory Mechanisms of the Mammalian Target of Rapamycin

123 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2003.Unexpectedly, mTOR has been found to shuttle between the nucleus and the cytoplasm, and this shuttling is required for its cytoplasmic signaling. I have further investigated the regulation and function of mTOR cytoplasmic-nuclear shuttling. A systematic screen of mTOR revealed a rev-like NES sequence within mTOR at amino acids 1281--1289, which displayed robust nuclear export activity in a reporter system. Mutation of the conserved leucines within this export site resulted in a loss of downstream signaling in vivo, despite retention of mTOR catalytic activity. Interestingly, the mTOR 1281--1289L/A mutant showed cytoplasmic staining similar to wild type mTOR, and did not accumulate in the nucleus upon LMB treatment. This suggests that the 1281--1289L/A mutations in mTOR disrupt nucleocytoplasmic shuttling activity. The nucleocytoplasmic shuttling of mTOR is likely a mechanism to lessen the probability of aberrant signaling, a necessary control for a protein that has an essential role in cell growth and proliferation.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD