Rictor and integrin-linked kinase interact and regulate Akt phosphorylation and cancer cell survival.
An unbiased proteomic screen to identify integrin-linked kinase (ILK) interactors revealed rictor as an ILK-binding protein. This finding was interesting because rictor, originally identified as a regulator of cytoskeletal dynamics, is also a component of mammalian target of rapamycin complex 2 (mTORC2), a complex implicated in Akt phosphorylation. These functions overlap with known ILK functions. Coimmunoprecipitation analyses confirmed this interaction, and ILK and rictor colocalized in membrane ruffles and leading edges of cancer cells. Yeast two-hybrid assays showed a direct interaction between the NH(2)- and COOH-terminal domains of rictor and the ILK kinase domain. Depletion of ILK and rictor in breast and prostate cancer cell lines resulted in inhibition of Akt Ser(473) phosphorylation and induction of apoptosis, whereas, in several cell lines, depletion of mTOR increased Akt phosphorylation. Akt and Ser(473)P-Akt were detected in ILK immunoprecipitates and small interfering RNA-mediated depletion of rictor, but not mTOR, inhibited the amount of Ser(473)P-Akt in the ILK complex. Expression of the NH(2)-terminal (1-398 amino acids) rictor domain also resulted in the inhibition of ILK-associated Akt Ser(473) phosphorylation. These data show that rictor regulates the ability of ILK to promote Akt phosphorylation and cancer cell survival.
McDonald
Paul C
PC
Department of Cancer Genetics, BC Cancer Research Centre, British Columbia Cancer Agency, Vancouver, BC, Canada.
Oloumi
Arusha
A
Mills
Julia
J
Dobreva
Iveta
I
Maidan
Mykola
M
Gray
Virginia
V
Wederell
Elizabeth D
ED
Bally
Marcel B
MB
Foster
Leonard J
LJ
Dedhar
Shoukat
S
D001943:Breast Neoplasms / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology; D002853:Chromatography, Liquid; D003599:Cytoskeleton / Q000378:metabolism; D015536:Down-Regulation; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D012694:Serine / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases; D053719:Tandem Mass Spectrometry; D014162:Transfection; D000099200:Scaffold Protein ILK
D002352:Carrier Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D012694:Serine; D058570:TOR Serine-Threonine Kinases; D000099200:Scaffold Protein ILK; C492571:RICTOR protein, human; C546842:MTOR protein, human