Growth or longevity: the TOR's decision on lifespan regulation.

TOR (target of rapamycin) pathway has been well known for its central role in growth control. Interestingly, recent studies also implicate the TOR pathway in lifespan regulation in various organisms ranging from budding yeast to mammals. TOR gains momentum in a study showing that rapamycin administration later in life significantly extends lifespan in mice. How the TOR kinase controls these two seemingly distinct biological processes is an especially intriguing question yet to be answered. Here, we summarize the literatures concerning TOR's role in growth control, stress response and lifespan regulation, hoping to obtain a better understanding of how cell growth and maintenance are balanced by TOR and how TOR-mediated shift in metabolisms or energy allocations may translate into lifespan extension at the organismal level. We also evaluate the undergoing efforts to target the TOR pathway for health in human, with focus on looking for new drugs that can bypass the unwanted side effects of rapamycin derivatives.