PLD2 forms a functional complex with mTOR/raptor to transduce mitogenic signals.
Mammalian target-of-rapamycin (mTOR), which is a master controller of cell growth, senses a mitogenic signal in part through the lipid second messenger phosphatidic acid (PA), generated by phospholipase D (PLD). To understand further which isozymes of PLD are involved in this process, we compared the effect of PLD isozymes on mTOR activation. We found that PLD2 has an essential role in mitogen-induced mTOR activation as the siRNA-mediated knockdown of PLD2, not of PLD1, profoundly reduced the phosphorylations of S6K1 and 4EBP1, well-known mTOR effectors. Furthermore, exogenous PA-induced mTOR activation was abrogated by PLD2 knockdown, but not by PLD1 knockdown. This abrogation was found to be the result of complex formation between PLD2 and mTOR/raptor. PLD2 possesses a TOS-like motif (Phe-Glu-Val-Gln-Val, a.a. 265-269), through which it interacts with raptor independently of the other TOS motif-containing proteins, S6K1 and 4EBP1. PLD2-dependent mTOR activation appears to require PLD2 binding to mTOR/raptor with lipase activity, since lipase-inactive PLD2 cannot trigger mTOR activation despite its ability to interact with mTOR/raptor. Abrogation of mitogen-dependent mTOR activation by PLD2 knockdown was rescued only by wild type PLD2, but not by raptor binding-deficient and lipase-inactive PLD2. Our results demonstrate the importance of localized PA generation for the mitogen-induced activation of mTOR, which is achieved by a specific interaction between PLD2 and mTOR/raptor.
Ha
Sang Hoon
SH
Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbook 790-784, Republic of Korea.
Kim
Do-Hyung
DH
Kim
Il-Shin
IS
Kim
Jung Hwan
JH
Lee
Mi Nam
MN
Lee
Hyun Ju
HJ
Kim
Jong Heon
JH
Jang
Sung Key
SK
Suh
Pann-Ghill
PG
Ryu
Sung Ho
SH
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D047468:Immunoprecipitation; D008934:Mitogens / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010739:Phospholipase D / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases; D014162:Transfection
D008934:Mitogens; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; C105606:phospholipase D2; D010739:Phospholipase D