Regulation of B-Raf kinase activity by tuberin and Rheb is mammalian target of rapamycin (mTOR)-independent

Magdalena Karbowniczek, Timothy Cash, Mitchell Cheung, Gavin P. Robertson, Aristotelis Astreinidis, Elizabeth Petri Henske

Research output: Contribution to journalArticle

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Abstract

Tuberous sclerosis complex (TSC) is a tumor suppressor gene syndrome with manifestations that can include seizures, mental retardation, autism, and tumors in the brain, retina, kidney, heart, and skin. The products of the TSC1 and TSC2 genes, hamartin and tuberin, respectively, heterodimerize and inhibit the mammalian target of rapamycin (mTOR). We found that tuberin expression increases p42/44 MAPK phosphorylation and B-Raf kinase activity. Short interfering RNA down-regulation of tuberin decreased the p42/44 MAPK phosphorylation and B-Raf activity. Expression of Rheb, the target of the GTPase-activating domain of tuberin, inhibited wild-type B-Raf kinase but not activated forms of B-Raf. The interaction of endogenous Rheb with B-Raf was enhanced by serum and by Ras overexpression. A farnesylation-defective mutant of Rheb co-immunoprecipitated with and inhibited B-Raf but did not activate ribosomal protein S6 kinase, indicating that farnesylation is not required for B-Raf inhibition by Rheb and that B-Raf inhibition and S6 kinase activation are separable activities of Rheb. Consistent with this, inhibition of B-Raf and p42/44 MAPK by Rheb was resistant to rapamycin in contrast to Rheb activation of S6 kinase, which is rapamycin-sensitive. Taken together these data demonstrate that inhibition of B-Raf kinase via Rheb is an mTOR-independent function of tuberin.

Original languageEnglish (US)
Pages (from-to)29930-29937
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number29
DOIs
StatePublished - Jul 16 2004
Externally publishedYes

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Proto-Oncogene Proteins B-raf
Sirolimus
Ribosomal Protein S6 Kinases
Mitogen-Activated Protein Kinase 1
Prenylation
Phosphorylation
Tumors
Genes
Chemical activation
Tuberous Sclerosis
GTP Phosphohydrolases
Autistic Disorder
Tumor Suppressor Genes
Brain Neoplasms
Intellectual Disability
Small Interfering RNA
Retina
Brain
Skin
Seizures

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Regulation of B-Raf kinase activity by tuberin and Rheb is mammalian target of rapamycin (mTOR)-independent. / Karbowniczek, Magdalena; Cash, Timothy; Cheung, Mitchell; Robertson, Gavin P.; Astreinidis, Aristotelis; Henske, Elizabeth Petri.

In: Journal of Biological Chemistry, Vol. 279, No. 29, 16.07.2004, p. 29930-29937.

Research output: Contribution to journalArticle

Karbowniczek, Magdalena ; Cash, Timothy ; Cheung, Mitchell ; Robertson, Gavin P. ; Astreinidis, Aristotelis ; Henske, Elizabeth Petri. / Regulation of B-Raf kinase activity by tuberin and Rheb is mammalian target of rapamycin (mTOR)-independent. In: Journal of Biological Chemistry. 2004 ; Vol. 279, No. 29. pp. 29930-29937.
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