The rapamycin and FKBP12 target (RAFT) displays phosphatidylinositol 4-kinase activity.
The immunosuppressant rapamycin prevents cell cycle progression in several mammalian cell lines and the yeast Saccharomyces cerevisiae. In mammalian cells, rapamycin binds to the small FK506-binding protein, FKBP12, allowing the drug-receptor complex to interact with the 289-kDa RAFT1/FRAP proteins. These proteins, along with their yeast homologs, TOR1/DRR1 and TOR2/DRR2, contain a C-terminal domain with amino acid homology to several phosphatidylinositol (PI) 4- and 3-kinases. However, no direct demonstration of kinase activity for this family of proteins has been reported. We now show that RAFT1, immunoprecipitated from rat brain and MG63 and HEK293 cells, contains PI 4-kinase activity and that rapamycin-FKBP12 has no effect on this activity. Thus, it is likely that, in vivo, rapamycin does not directly inhibit the PI 4-kinase activity and affects the RAFT1/FRAP protein through another mechanism.
Sabatini
D M
DM
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Pierchala
B A
BA
Barrow
R K
RK
Schell
M J
MJ
Snyder
S H
SH
D019870:1-Phosphatidylinositol 4-Kinase; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000187:drug effects / Q000378:metabolism*; D011090:Polyenes / Q000378:metabolism; D011233:Precipitin Tests; D051381:Rats; D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; D022021:Tacrolimus Binding Proteins; D000077191:Wortmannin
D000730:Androstadienes; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D011090:Polyenes; D029701:Saccharomyces cerevisiae Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); C546845:mTOR protein, rat; D019870:1-Phosphatidylinositol 4-Kinase; C441760:PIK1 protein, S cerevisiae; D058570:TOR Serine-Threonine Kinases; D022021:Tacrolimus Binding Proteins; D020123:Sirolimus; D000077191:Wortmannin