Tor signalling in bugs, brain and brawn.

TOR--a highly conserved atypical protein kinase and the 'target of rapamycin', an immunosuppressant and anti-cancer drug--controls cell growth. TOR controls the growth of proliferating yeast, fly and mammalian cells in response to nutrients. Recent findings, however, indicate that TOR also controls the growth of non-proliferating cells, such as neurons and muscle cells. Furthermore, TOR, by associating with regulatory proteins and inhibiting phosphatases, controls the activity of multiphosphorylated effectors.