The Mtor Substrate S6 Kinase 1 (S6K1)
The Journal of Neuroscience, July 26, 2017 • 37(30):7079–7095 • 7079 Cellular/Molecular The mTOR Substrate S6 Kinase 1 (S6K1) Is a Negative Regulator of Axon Regeneration and a Potential Drug Target for Central Nervous System Injury X Hassan Al-Ali,1,2,3* Ying Ding,5,6* Tatiana Slepak,1* XWei Wu,5 Yan Sun,5,7 Yania Martinez,1 Xiao-Ming Xu,5 Vance P. Lemmon,1,3 and XJohn L. Bixby1,3,4 1Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, Florida 33136, 2Peggy and Harold Katz Family Drug Discovery Center, University of Miami Miller School of Medicine, Miami, Florida 33136, 3Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, Florida 33136, 4Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, 5Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery, Indiana University School of Medicine, Indianapolis, Indiana 46202, 6Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong 510080, China, and 7Department of Anatomy, Histology and Embryology, School of Basic Medical Sciences, Fudan University, Shanghai, 200032, China Themammaliantargetofrapamycin(mTOR)positivelyregulatesaxongrowthinthemammaliancentralnervoussystem(CNS).Althoughaxon regeneration and functional recovery from CNS injuries are typically limited, knockdown or deletion of PTEN, a negative regulator of mTOR, increases mTOR activity and induces robust axon growth and regeneration. It has been suggested that inhibition of S6 kinase 1 (S6K1, gene symbol: RPS6KB1), a prominent mTOR target, would blunt mTOR’s positive effect on axon growth. In contrast to this expectation, we demon- strate that inhibition of S6K1 in CNS neurons promotes neurite outgrowth in vitro by twofold to threefold.
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