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      Differential Role of PTEN Phosphatase in Chemotactic Growth Cone Guidance*

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          Abstract

          Background: The phosphatase PTEN is implicated in suppressing neuroregeneration following injury.

          Results: Chemorepulsion of axons by distinct cues, but not chemoattraction, correlates with PTEN activity, depression of phosphatidylinositol signaling, and remodeling of integrin adhesions.

          Conclusion: PTEN mediates chemorepulsion selectively.

          Significance: Suppressing PTEN activity may block repulsion by negative cues after injury while permitting attractive guidance of regenerating axons.

          Abstract

          Negatively targeting the tumor suppressor and phosphoinositide phosphatase PTEN (phosphatase and tensin homologue) promotes axon regrowth after injury. How PTEN functions in axon guidance has remained unknown. Here we report the differential role of PTEN in chemotactic guidance of axonal growth cones. Down-regulating PTEN expression in Xenopus laevis spinal neurons selectively abolished growth cone chemorepulsion but permitted chemoattraction. These findings persisted during cAMP-dependent switching of turning behaviors. Live cell imaging using a GFP biosensor revealed rapid PTEN-dependent depression of phosphatidylinositol 3,4,5-trisphosphate levels in the growth cone induced by the repellent myelin-associated glycoprotein. Moreover, down-regulating PTEN expression blocked negative remodeling of β1-integrin adhesions triggered by myelin-associated glycoprotein, yet permitted integrin clustering by a positive chemotropic treatment. Thus, PTEN negatively regulates growth cone phosphatidylinositol 3,4,5-trisphosphate levels and mediates chemorepulsion, whereas chemoattraction is PTEN-independent. Regenerative therapies targeting PTEN may therefore suppress growth cone repulsion to soluble cues while permitting attractive guidance, an essential feature for re-forming functional neural circuits.

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          Most cited references 31

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          Promoting axon regeneration in the adult CNS by modulation of the PTEN/mTOR pathway.

           Bin He,  Yang Hu,  Bin Cai (2008)
          The failure of axons to regenerate is a major obstacle for functional recovery after central nervous system (CNS) injury. Removing extracellular inhibitory molecules results in limited axon regeneration in vivo. To test for the role of intrinsic impediments to axon regrowth, we analyzed cell growth control genes using a virus-assisted in vivo conditional knockout approach. Deletion of PTEN (phosphatase and tensin homolog), a negative regulator of the mammalian target of rapamycin (mTOR) pathway, in adult retinal ganglion cells (RGCs) promotes robust axon regeneration after optic nerve injury. In wild-type adult mice, the mTOR activity was suppressed and new protein synthesis was impaired in axotomized RGCs, which may contribute to the regeneration failure. Reactivating this pathway by conditional knockout of tuberous sclerosis complex 1, another negative regulator of the mTOR pathway, also leads to axon regeneration. Thus, our results suggest the manipulation of intrinsic growth control pathways as a therapeutic approach to promote axon regeneration after CNS injury.
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            PTEN Deletion Enhances the Regenerative Ability of Adult Corticospinal Neurons

            Despite the essential role of the corticospinal tract (CST) in controlling voluntary movements, successful regeneration of large numbers of injured CST axons beyond a spinal cord lesion has never been achieved. Here we demonstrate a critical involvement of PTEN/mTOR in controlling the regenerative capacity of mouse corticospinal neurons. Upon the completion of development, the regrowth potential of CST axons lost and this is accompanied by a down-regulation of mTOR activity in corticospinal neurons. Axonal injury further diminishes neuronal mTOR activity in these neurons. Forced up-regulation of mTOR activity in corticospinal neurons by conditional deletion of PTEN, a negative regulator of mTOR, enhances compensatory sprouting of uninjured CST axons and even more strikingly, enables successful regeneration of a cohort of injured CST axons past a spinal cord lesion. Furthermore, these regenerating CST axons possess the ability to reform synapses in spinal segments distal to the injury. Thus, modulating neuronal intrinsic PTEN/mTOR activity represents a potential therapeutic strategy for promoting axon regeneration and functional repair after adult spinal cord injury.
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              Inhibition of cell migration, spreading, and focal adhesions by tumor suppressor PTEN.

               S Aota,  Daniel Parsons,  J Gu (1998)
              The tumor suppressor PTEN is a phosphatase with sequence similarity to the cytoskeletal protein tensin. Here the cellular roles of PTEN were investigated. Overexpression of PTEN inhibited cell migration, whereas antisense PTEN enhanced migration. Integrin-mediated cell spreading and the formation of focal adhesions were down-regulated by wild-type PTEN but not by PTEN with an inactive phosphatase domain. PTEN interacted with the focal adhesion kinase FAK and reduced its tyrosine phosphorylation. Overexpression of FAK partially antagonized the effects of PTEN. Thus, PTEN phosphatase may function as a tumor suppressor by negatively regulating cell interactions with the extracellular matrix.
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                Author and article information

                Journal
                J Biol Chem
                J. Biol. Chem
                jbc
                jbc
                JBC
                The Journal of Biological Chemistry
                American Society for Biochemistry and Molecular Biology (9650 Rockville Pike, Bethesda, MD 20814, U.S.A. )
                0021-9258
                1083-351X
                19 July 2013
                17 June 2013
                17 June 2013
                : 288
                : 29
                : 20837-20842
                Affiliations
                From the []Department of Neurologic Surgery,
                [§ ]Medical Scientist Training Program, and
                []Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905
                Author notes
                [2 ] To whom correspondence should be addressed: College of Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN 55905. Tel.: 507-284-5275; Fax: 507-284-3383; E-mail: Henley.john@ 123456mayo.edu .
                [1]

                Present address: Dept. of Neurobiology, Harvard Medical School, Boston, MA 02115.

                Article
                C113.487066
                10.1074/jbc.C113.487066
                3774355
                23775074
                © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.

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                Creative Commons Attribution Unported License applies to Author Choice Articles

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                Funding
                Funded by: National Institutes of Health
                Award ID: NS067311
                Award ID: NS080322
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