Mechanism of action of rapamycin: New insights into the regulation of G1-phase progression in eukaryotic cells

Abstract
The immunosuppressant drug, rapamycin (RAP), is a potent inhibitor of IL-2-dependent T-cell proliferation. The antiproliferative effect of RAP is mediated through the formation of an active complex with its cytosolic receptor protein, FKBP12. The molecular target of the FKBP12-RAP complex is a putative lipid kinase termed the mammalian Target Of Rapamycin (mTOR). This review will discuss recent findings suggesting that mTOR is a novel regulator of G1 to S-phase progression in eukaryotic cells.