title: Rictor regulates MMP-9 activity and invasion through Raf-1-MEK-ERK signaling pathway in glioma cells.
abstract: Glioblastoma multiforme (GBM) is the most common and highly aggressive type of primary brain tumor. Tumor-associated macrophages (TAMs) secrete TNF-α that activates important survival pathways including Akt (PKB)/mTOR network. The mammalian target of rapamycin (mTOR) network functions downstream of PI3K/Akt pathway to regulate cell growth, proliferation and survival. mTOR exists in two distinct complexes-mTORC1 and mTORC2 that differ in their components and sensitivity to rapamycin. The rapamycin-insensitive complex (mTORC2) consists of mTOR, mLST8, Rictor, mSin1 and Protor and regulates the actin cytoskeleton in addition to activating Akt (protein kinase B). The present study aimed to investigate the role of Rictor-a core component of mTORC2 in regulating proliferation, survival, and invasion in gliomas. siRNA-mediated loss of Rictor function in human glioma cell lines, LN18 and LN229 and in primary GBM cells resulted in elevated expression and activity of MMP-9 and significant increase in the invasive potential of these cells. Mechanistic studies revealed that the activation of Raf-1-MEK-ERK pathway was essential for induction of MMP-9 activity and enhanced invasion. Interestingly, ablation of Rictor did not affect TNF-α-induced MMP-9 activity and invasiveness suggesting that TNF-α in the microenvironment of tumor might overrule the function of Rictor as a negative regulator of MMP-9 and invasion. Silencing Rictor had no effect on the survival or proliferation in the cell lines in the presence or absence of TNF-α. Our findings identify a role for Rictor in bridging two major pathways-Akt (PKB)/mTOR and Raf-1-MEK-ERK in regulating MMP-9 activity and invasion of glioma tumor cells.
authors.affiliation: National Centre for Cell Science (NCCS), Ganeshkhind, Pune, Maharashtra, India.
authors.forename: Gowry
authors.initials: G
authors.lastname: Das
authors.forename: Anjali
authors.initials: A
authors.lastname: Shiras
authors.forename: Karthik
authors.initials: K
authors.lastname: Shanmuganandam
authors.forename: Padma
authors.initials: P
authors.lastname: Shastry
mesh_terms: D015153:Blotting, Western; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism*; D002465:Cell Movement; D049109:Cell Proliferation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D010766:Phosphorylation; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; C492571:RICTOR protein, human; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D014409:Tumor Necrosis Factor-alpha; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020780:Matrix Metalloproteinase 9