Specification of Neuronal Polarity Regulated by Local Translation of CRMP2 and Tau via the mTOR-p70S6K Pathway (2009)

Mammalian target of rapamycin (mTOR) is an important regulator of neuronal development and functions. Although it was reported recently that mTOR signaling is critical for neuronal polarity, the underlying mechanism remains unclear. Here, we describe the molecular pathway of mTOR-dependent axon specification, in which the collapsing response mediator protein 2 (CRMP2) and Tau are major downstream targets. The activity of mTOR effector 70-kDa ribosomal protein S6 kinase (p70S6K) specifically increases in the axon during neuronal polarity formation. The mTOR inhibitor rapamycin suppresses the translation of some neuronal polarity proteins, including CRMP2 and Tau, thereby inhibiting axon formation. In contrast, constitutively active p70S6K up-regulates the translation of these molecules, thus inducing multiple axons. Exogenous CRMP2 and Tau facilitate axon formation, even in the presence of rapamycin. In the 5′-untranslated region of Tau and CRMP2 mRNAs, we identified a 5′-terminal oligopyrimidine tract, which mediates mTOR-governed protein synthesis. The 5′-terminal oligopyrimidine tract sequences of CRMP2 and Tau mRNAs strongly contribute to the up-regulation of their translation in the axon in response to the axonal activation of the mTOR-p70S6K pathway. Taken together, we conclude that the local translation of CRMP2 and Tau, regulated by mTOR-p70S6K, is critical for the specification of neuronal polarity. Mammalian target of rapamycin (mTOR) is an important regulator of neuronal development and functions. Although it was reported recently that mTOR signaling is critical for neuronal polarity, the underlying mechanism remains unclear. Here, we describe the molecular pathway of mTOR-dependent axon specification, in which the collapsing response mediator protein 2 (CRMP2) and Tau are major downstream targets. The activity of mTOR effector 70-kDa ribosomal protein S6 kinase (p70S6K) specifically increases in the axon during neuronal polarity formation. The mTOR inhibitor rapamycin suppresses the translation of some neuronal polarity proteins, including CRMP2 and Tau, thereby inhibiting axon formation. In contrast, constitutively active p70S6K up-regulates the translation of these molecules, thus inducing multiple axons. Exogenous CRMP2 and Tau facilitate axon formation, even in the presence of rapamycin. In the 5′-untranslated region of Tau and CRMP2 mRNAs, we identified a 5′-terminal oligopyrimidine tract, which mediates mTOR-governed protein synthesis. The 5′-terminal oligopyrimidine tract sequences of CRMP2 and Tau mRNAs strongly contribute to the up-regulation of their translation in the axon in response to the axonal activation of the mTOR-p70S6K pathway. Taken together, we conclude that the local translation of CRMP2 and Tau, regulated by mTOR-p70S6K, is critical for the specification of neuronal polarity. To function, developing neurons must establish axonal-dendritic polarity. The polarization processes have been well studied in cultured hippocampal neurons (1Dotti C.G. Sullivan C.A. Banker G.A. J. Neurosci. 1988; 8: 1454-1468Crossref PubMed Google Scholar, 2Craig A.M. Banker G. Annu. Rev. Neurosci. 1994; 17: 267-310Crossref PubMed Scopus (638) Google Scholar). They first form lamellipodia and small protrusion veils shortly after plating (stage 1) and then extend several immature neurites within 12–24 h (stage 2). One of the neurites rapidly elongates and becomes the axon, whereas the others become dendrites (stage 3). During these processes, a number of molecules coordinately control the axon specification (3Arimura N. Kaibuchi K. Nat. Rev. Neurosci. 2007; 8: 194-205Crossref PubMed Scopus (481) Google Scholar). These molecules spatially regulate cytoskeletal networks of actin filaments and microtubules for specification and maintenance of a single axon.Mammalian target of rapamycin (mTOR) 2The abbreviations used are: mTORmammalian target of rapamycinCAconstitutively activeCRMP2collapsing response mediator protein 2DIVdays in vitroDNdominant negativeEGFPenhanced green fluorescent proteineIF-4Eeukaryotic translation initiation factor 4E4E-BP1eIF-4E-binding protein 1GAPDHglyceraldehyde-3-phosphate dehydrogenaseGFPgreen fluorescent proteinMAP2microtubule-associated protein 2p70S6K70-kDa ribosomal protein S6 kinaseRLM-5′-RACERNA ligase-mediated rapid amplification of 5′-cDNA endsRTreverse transcriptionSADsynapses of the amphid-detective5′-TOP5′-terminal oligopyrimidine tractTSCtuberous sclerosis complexUTRuntranslated region. 2The abbreviations used are: mTORmammalian target of rapamycinCAconstitutively activeCRMP2collapsing response mediator protein 2DIVdays in vitroDNdominant negativeEGFPenhanced green fluorescent proteineIF-4Eeukaryotic translation initiation factor 4E4E-BP1eIF-4E-binding protein 1GAPDHglyceraldehyde-3-phosphate dehydrogenaseGFPgreen fluorescent proteinMAP2microtubule-associated protein 2p70S6K70-kDa ribosomal protein S6 kinaseRLM-5′-RACERNA ligase-mediated rapid amplification of 5′-cDNA endsRTreverse transcriptionSADsynapses of the amphid-detective5′-TOP5′-terminal oligopyrimidine tractTSCtuberous sclerosis complexUTRuntranslated region. is a serine/threonine protein kinase and mainly controls protein synthesis via phosphorylation of its downstream targets, such as eukaryotic translation initiation factor 4E (eIF-4E)-binding protein 1 (4E-BP1) and 70-kDa ribosomal S6 protein kinase (p70S6K) (4Hay N. Sonenberg N. Genes Dev. 2004; 18: 1926-1945Crossref PubMed Scopus (3401) Google Scholar). In the nervous system, mTOR plays important roles in neuronal survival, dendritic arbor formation, synaptic plasticity, learning, and memory (5Swiech L. Perycz M. Malik A. Jaworski J. Biochim. Biophys. Acta. 2008; 1784: 116-132Crossref PubMed Scopus (287) Google Scholar). Notably, in the regulation of synaptic plasticity, a number of mRNAs are locally translated via activation of the mTOR pathway in response to extracellular signals (5Swiech L. Perycz M. Malik A. Jaworski J. Biochim. Biophys. Acta. 2008; 1784: 116-132Crossref PubMed Scopus (287) Google Scholar, 6Kelleher 3rd, R.J. Govindarajan A. Tonegawa S. Neuron. 2004; 44: 59-73Abstract Full Text Full Text PDF PubMed Scopus (480) Google Scholar, 7Richter J.D. Klann E. Genes Dev. 2009; 23: 1-11Crossref PubMed Scopus (279) Google Scholar). Recently, two research groups reported that the mTOR pathway is also critical for the formation of neuronal polarity (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar, 9Li Y.H. Werner H. Püschel A.W. J. Biol. Chem. 2008; 283: 33784-33792Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar). They proposed that the mTOR pathway controls the synthesis of polarity proteins, such as synapses of the amphid-detective (SAD) kinases (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar) and Rap1 (9Li Y.H. Werner H. Püschel A.W. J. Biol. Chem. 2008; 283: 33784-33792Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar), and therefore regulates the neuronal polarity. However, the underlying molecular mechanism remains to be fully understood. Here, we demonstrate that p70S6K is necessary and sufficient for the mTOR-controlled axon formation as a downstream effector of mTOR. The mTOR-p70S6K pathway regulates translation of several neuronal polarity genes, including SAD kinases and Rap1. In particular, the expressions of collapsing response mediator protein 2 (CRMP2) and microtubule-associated protein Tau are highly dependent on mTOR-governed protein synthesis. We further identified a 5′-terminal oligopyrimidine (5′-TOP) tract, which mediates mTOR-governed protein synthesis (10Ruvinsky I. Meyuhas O. Trends Biochem. Sci. 2006; 31: 342-348Abstract Full Text Full Text PDF PubMed Scopus (594) Google Scholar), in the 5′-UTRs of CRMP2 and Tau mRNAs. In the axon of developing neurons, the translation of CRMP2 and Tau mRNAs is spatially controlled by the mTOR-p70S6K pathway via the 5′-TOP sequences, resulting in accumulation of CRMP2 and Tau proteins in the axon. Thus, our study substantially improves understanding of molecular mechanisms underlying the mTOR-dependent development of neuronal polarity.DISCUSSIONIn this paper, we reported a novel finding that p70S6K was an important mTOR effector in the development of neuronal polarity. The activity of p70S6K was specifically increased in the axon during neuronal polarity development (Fig. 2C), and CA-S6K-expressing neurons formed multiple axons even in the presence of rapamycin (Fig. 2). In contrast, DN-S6K strongly inhibited axon formation (Fig. 1), indicating that the activation of p70S6K is necessary and sufficient for the formation of mTOR-governed neuronal polarity. In addition, we showed that CRMP2, Tau, and Rap1, all well known as essential factors for the establishment of neuronal polarity (3Arimura N. Kaibuchi K. Nat. Rev. Neurosci. 2007; 8: 194-205Crossref PubMed Scopus (481) Google Scholar), are components of the mTOR-p70S6K pathway. The expression of CRMP2 and Tau was particularly dependent on mTOR-p70S6K-governed protein synthesis (Fig. 4). Exogenous overexpression of CRMP2 and Tau rescued the and polarity and that are critical downstream of the pathway in the establishment of neuronal polarity. CRMP2 and Tau are known to roles in expression of CRMP2 and Tau rescued the and polarity their single the was and that have a in axon formation. CRMP2 and Tau mRNAs a 5′-TOP and their translation was controlled via the 5′-TOP and Taken together, these that the activation of p70S6K in the axon of developing neurons to the local translation of CRMP2 and Tau by the maintenance and of axon mRNAs for proteins translation is controlled by mTOR have a 5′-TOP (10Ruvinsky I. Meyuhas O. Trends Biochem. Sci. 2006; 31: 342-348Abstract Full Text Full Text PDF PubMed Scopus (594) Google Scholar, M. M. Biochem. 2006; PubMed Scopus Google Scholar). The of our that the CRMP2 is a 5′-TOP (Fig. The multiple is highly in that the translation of CRMP2 is important for its We also that the Tau a tract its (Fig. translation of CRMP2 and Tau mRNAs via 5′-TOP in the axonal accumulation of CRMP2 and Tau proteins (Fig. and and and In it is well that the Tau is to the of the axon via its axonal which be in the accumulation of Tau proteins in the axon J. L. I. Neuron. Full Text PDF PubMed Scopus Google Scholar, S. G. L. I. J. Neurosci. PubMed Google Scholar). In addition, H. A. Kaibuchi K. J. PubMed Scopus Google Scholar) reported that to CRMP2 and it to the axon. These mechanisms for the axonal of CRMP2 and Tau proteins regulate the specification and maintenance of a single was first reported as a downstream effector in the mTOR-governed translation of 5′-TOP mRNAs S. G. J. PubMed Scopus Google Scholar). and that p70S6K is sufficient for the regulation of 5′-TOP mRNAs H. E. M. G. M. J. Meyuhas O. Biol. PubMed Scopus Google Scholar, M. M. J. M. S. G. Biol. 2004; PubMed Scopus Google Scholar), the that and the translation of 5′-TOP mRNAs. In hippocampal neurons, the activation of p70S6K was for axon specification, and rescued the polarity 1 and 2). increased the translation of CRMP2 and Tau even in the and and the translation of and We further that the translation of 5′-TOP O. J. Biochem. PubMed Scopus Google Scholar) was also by via its 5′-TOP 4). These that p70S6K controls the translation of CRMP2 and Tau mRNAs via the 5′-TOP sequences in developing hippocampal (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar) recently reported that the sclerosis proteins, which are of the axon formation. They identified the SAD increased in to their we that the expression of SAD kinases by rapamycin (Fig. 4). (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar) also reported that the expression of SAD kinases are by rapamycin that mTOR activity is for the expression of SAD kinases in developing cultured hippocampal the expression of SAD kinases in the CA-S6K-expressing neurons (Fig. the that protein of SAD kinases be by p70S6K of translation protein Thus, the regulation of SAD kinases must be We SAD kinases to be in the axon, and and SAD kinases showed of the polarity indicating that SAD kinases are important for the axon (9Li Y.H. Werner H. Püschel A.W. J. Biol. Chem. 2008; 283: 33784-33792Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar) also reported the regulation of neuronal polarity by the pathway. In their was identified as a critical polarity protein regulated by mTOR-dependent protein synthesis. We also the mTOR of Rap1 expression and 4). expression increased the of in the and hippocampal neurons, it was CRMP2 Tau and They also the of in axon formation as a downstream effector of mTOR. We that neurons form a that is in the neuronal polarity formation. However, and rapamycin (Fig. 1), by a of including that of overexpression of which that been by multiple axons. However, p70S6K was necessary and sufficient for mTOR-controlled axon formation, as Thus, p70S6K is a effector of the mTOR pathway in the development of neuronal mTOR-p70S6K-governed protein synthesis is for the development of neuronal polarity. The activation of the mTOR pathway in the axon the local translation of several polarity genes, CRMP2 and CRMP2 and Tau specifically in the axon via local to the specification, formation, and maintenance of a single axon. Thus, this study the mechanism of mTOR-controlled axon formation and the establishment of neuronal polarity. To function, developing neurons must establish axonal-dendritic polarity. The polarization processes have been well studied in cultured hippocampal neurons (1Dotti C.G. Sullivan C.A. Banker G.A. J. Neurosci. 1988; 8: 1454-1468Crossref PubMed Google Scholar, 2Craig A.M. Banker G. Annu. Rev. Neurosci. 1994; 17: 267-310Crossref PubMed Scopus (638) Google Scholar). They first form lamellipodia and small protrusion veils shortly after plating (stage 1) and then extend several immature neurites within 12–24 h (stage 2). One of the neurites rapidly elongates and becomes the axon, whereas the others become dendrites (stage 3). During these processes, a number of molecules coordinately control the axon specification (3Arimura N. Kaibuchi K. Nat. Rev. Neurosci. 2007; 8: 194-205Crossref PubMed Scopus (481) Google Scholar). These molecules spatially regulate cytoskeletal networks of actin filaments and microtubules for specification and maintenance of a single axon. Mammalian target of rapamycin (mTOR) 2The abbreviations used are: mTORmammalian target of rapamycinCAconstitutively activeCRMP2collapsing response mediator protein 2DIVdays in vitroDNdominant negativeEGFPenhanced green fluorescent proteineIF-4Eeukaryotic translation initiation factor 4E4E-BP1eIF-4E-binding protein 1GAPDHglyceraldehyde-3-phosphate dehydrogenaseGFPgreen fluorescent proteinMAP2microtubule-associated protein 2p70S6K70-kDa ribosomal protein S6 kinaseRLM-5′-RACERNA ligase-mediated rapid amplification of 5′-cDNA endsRTreverse transcriptionSADsynapses of the amphid-detective5′-TOP5′-terminal oligopyrimidine tractTSCtuberous sclerosis complexUTRuntranslated region. 2The abbreviations used are: mTORmammalian target of rapamycinCAconstitutively activeCRMP2collapsing response mediator protein 2DIVdays in vitroDNdominant negativeEGFPenhanced green fluorescent proteineIF-4Eeukaryotic translation initiation factor 4E4E-BP1eIF-4E-binding protein 1GAPDHglyceraldehyde-3-phosphate dehydrogenaseGFPgreen fluorescent proteinMAP2microtubule-associated protein 2p70S6K70-kDa ribosomal protein S6 kinaseRLM-5′-RACERNA ligase-mediated rapid amplification of 5′-cDNA endsRTreverse transcriptionSADsynapses of the amphid-detective5′-TOP5′-terminal oligopyrimidine tractTSCtuberous sclerosis complexUTRuntranslated region. is a serine/threonine protein kinase and mainly controls protein synthesis via phosphorylation of its downstream targets, such as eukaryotic translation initiation factor 4E (eIF-4E)-binding protein 1 (4E-BP1) and 70-kDa ribosomal S6 protein kinase (p70S6K) (4Hay N. Sonenberg N. Genes Dev. 2004; 18: 1926-1945Crossref PubMed Scopus (3401) Google Scholar). In the nervous system, mTOR plays important roles in neuronal survival, dendritic arbor formation, synaptic plasticity, learning, and memory (5Swiech L. Perycz M. Malik A. Jaworski J. Biochim. Biophys. Acta. 2008; 1784: 116-132Crossref PubMed Scopus (287) Google Scholar). Notably, in the regulation of synaptic plasticity, a number of mRNAs are locally translated via activation of the mTOR pathway in response to extracellular signals (5Swiech L. Perycz M. Malik A. Jaworski J. Biochim. Biophys. Acta. 2008; 1784: 116-132Crossref PubMed Scopus (287) Google Scholar, 6Kelleher 3rd, R.J. Govindarajan A. Tonegawa S. Neuron. 2004; 44: 59-73Abstract Full Text Full Text PDF PubMed Scopus (480) Google Scholar, 7Richter J.D. Klann E. Genes Dev. 2009; 23: 1-11Crossref PubMed Scopus (279) Google Scholar). Recently, two research groups reported that the mTOR pathway is also critical for the formation of neuronal polarity (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar, 9Li Y.H. Werner H. Püschel A.W. J. Biol. Chem. 2008; 283: 33784-33792Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar). They proposed that the mTOR pathway controls the synthesis of polarity proteins, such as synapses of the amphid-detective (SAD) kinases (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar) and Rap1 (9Li Y.H. Werner H. Püschel A.W. J. Biol. Chem. 2008; 283: 33784-33792Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar), and therefore regulates the neuronal polarity. However, the underlying molecular mechanism remains to be fully understood. Here, we demonstrate that p70S6K is necessary and sufficient for the mTOR-controlled axon formation as a downstream effector of mTOR. The mTOR-p70S6K pathway regulates translation of several neuronal polarity genes, including SAD kinases and Rap1. In particular, the expressions of collapsing response mediator protein 2 (CRMP2) and microtubule-associated protein Tau are highly dependent on mTOR-governed protein synthesis. We further identified a 5′-terminal oligopyrimidine (5′-TOP) tract, which mediates mTOR-governed protein synthesis (10Ruvinsky I. Meyuhas O. Trends Biochem. Sci. 2006; 31: 342-348Abstract Full Text Full Text PDF PubMed Scopus (594) Google Scholar), in the 5′-UTRs of CRMP2 and Tau mRNAs. In the axon of developing neurons, the translation of CRMP2 and Tau mRNAs is spatially controlled by the mTOR-p70S6K pathway via the 5′-TOP sequences, resulting in accumulation of CRMP2 and Tau proteins in the axon. Thus, our study substantially improves understanding of molecular mechanisms underlying the mTOR-dependent development of neuronal polarity. target of rapamycin constitutively active collapsing response mediator protein 2 in green fluorescent protein eukaryotic translation initiation factor 4E protein 1 green fluorescent protein microtubule-associated protein 2 70-kDa ribosomal protein S6 kinase ligase-mediated rapid amplification of 5′-cDNA synapses of the amphid-detective 5′-terminal oligopyrimidine tract sclerosis region. target of rapamycin constitutively active collapsing response mediator protein 2 in green fluorescent protein eukaryotic translation initiation factor 4E protein 1 green fluorescent protein microtubule-associated protein 2 70-kDa ribosomal protein S6 kinase ligase-mediated rapid amplification of 5′-cDNA synapses of the amphid-detective 5′-terminal oligopyrimidine tract sclerosis region. this paper, we reported a novel finding that p70S6K was an important mTOR effector in the development of neuronal polarity. The activity of p70S6K was specifically increased in the axon during neuronal polarity development (Fig. 2C), and CA-S6K-expressing neurons formed multiple axons even in the presence of rapamycin (Fig. 2). In contrast, DN-S6K strongly inhibited axon formation (Fig. 1), indicating that the activation of p70S6K is necessary and sufficient for the formation of mTOR-governed neuronal polarity. In addition, we showed that CRMP2, Tau, and Rap1, all well known as essential factors for the establishment of neuronal polarity (3Arimura N. Kaibuchi K. Nat. Rev. Neurosci. 2007; 8: 194-205Crossref PubMed Scopus (481) Google Scholar), are components of the mTOR-p70S6K pathway. The expression of CRMP2 and Tau was particularly dependent on mTOR-p70S6K-governed protein synthesis (Fig. 4). Exogenous overexpression of CRMP2 and Tau rescued the and polarity and that are critical downstream of the pathway in the establishment of neuronal polarity. CRMP2 and Tau are known to roles in expression of CRMP2 and Tau rescued the and polarity their single the was and that have a in axon formation. CRMP2 and Tau mRNAs a 5′-TOP and their translation was controlled via the 5′-TOP and Taken together, these that the activation of p70S6K in the axon of developing neurons to the local translation of CRMP2 and Tau by the maintenance and of axon mRNAs for proteins translation is controlled by mTOR have a 5′-TOP (10Ruvinsky I. Meyuhas O. Trends Biochem. Sci. 2006; 31: 342-348Abstract Full Text Full Text PDF PubMed Scopus (594) Google Scholar, M. M. Biochem. 2006; PubMed Scopus Google Scholar). The of our that the CRMP2 is a 5′-TOP (Fig. The multiple is highly in that the translation of CRMP2 is important for its We also that the Tau a tract its (Fig. translation of CRMP2 and Tau mRNAs via 5′-TOP in the axonal accumulation of CRMP2 and Tau proteins (Fig. and and and In it is well that the Tau is to the of the axon via its axonal which be in the accumulation of Tau proteins in the axon J. L. I. Neuron. Full Text PDF PubMed Scopus Google Scholar, S. G. L. I. J. Neurosci. PubMed Google Scholar). In addition, H. A. Kaibuchi K. J. PubMed Scopus Google Scholar) reported that to CRMP2 and it to the axon. These mechanisms for the axonal of CRMP2 and Tau proteins regulate the specification and maintenance of a single was first reported as a downstream effector in the mTOR-governed translation of 5′-TOP mRNAs S. G. J. PubMed Scopus Google Scholar). and that p70S6K is sufficient for the regulation of 5′-TOP mRNAs H. E. M. G. M. J. Meyuhas O. Biol. PubMed Scopus Google Scholar, M. M. J. M. S. G. Biol. 2004; PubMed Scopus Google Scholar), the that and the translation of 5′-TOP mRNAs. In hippocampal neurons, the activation of p70S6K was for axon specification, and rescued the polarity 1 and 2). increased the translation of CRMP2 and Tau even in the and and the translation of and We further that the translation of 5′-TOP O. J. Biochem. PubMed Scopus Google Scholar) was also by via its 5′-TOP 4). These that p70S6K controls the translation of CRMP2 and Tau mRNAs via the 5′-TOP sequences in developing hippocampal (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar) recently reported that the sclerosis proteins, which are of the axon formation. They identified the SAD increased in to their we that the expression of SAD kinases by rapamycin (Fig. 4). (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar) also reported that the expression of SAD kinases are by rapamycin that mTOR activity is for the expression of SAD kinases in developing cultured hippocampal the expression of SAD kinases in the CA-S6K-expressing neurons (Fig. the that protein of SAD kinases be by p70S6K of translation protein Thus, the regulation of SAD kinases must be We SAD kinases to be in the axon, and and SAD kinases showed of the polarity indicating that SAD kinases are important for the axon (9Li Y.H. Werner H. Püschel A.W. J. Biol. Chem. 2008; 283: 33784-33792Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar) also reported the regulation of neuronal polarity by the pathway. In their was identified as a critical polarity protein regulated by mTOR-dependent protein synthesis. We also the mTOR of Rap1 expression and 4). expression increased the of in the and hippocampal neurons, it was CRMP2 Tau and They also the of in axon formation as a downstream effector of mTOR. We that neurons form a that is in the neuronal polarity formation. However, and rapamycin (Fig. 1), by a of including that of overexpression of which that been by multiple axons. However, p70S6K was necessary and sufficient for mTOR-controlled axon formation, as Thus, p70S6K is a effector of the mTOR pathway in the development of neuronal mTOR-p70S6K-governed protein synthesis is for the development of neuronal polarity. The activation of the mTOR pathway in the axon the local translation of several polarity genes, CRMP2 and CRMP2 and Tau specifically in the axon via local to the specification, formation, and maintenance of a single axon. Thus, this study the mechanism of mTOR-controlled axon formation and the establishment of neuronal polarity. In this paper, we reported a novel finding that p70S6K was an important mTOR effector in the development of neuronal polarity. The activity of p70S6K was specifically increased in the axon during neuronal polarity development (Fig. 2C), and CA-S6K-expressing neurons formed multiple axons even in the presence of rapamycin (Fig. 2). In contrast, DN-S6K strongly inhibited axon formation (Fig. 1), indicating that the activation of p70S6K is necessary and sufficient for the formation of mTOR-governed neuronal polarity. In addition, we showed that CRMP2, Tau, and Rap1, all well known as essential factors for the establishment of neuronal polarity (3Arimura N. Kaibuchi K. Nat. Rev. Neurosci. 2007; 8: 194-205Crossref PubMed Scopus (481) Google Scholar), are components of the mTOR-p70S6K pathway. The expression of CRMP2 and Tau was particularly dependent on mTOR-p70S6K-governed protein synthesis (Fig. 4). Exogenous overexpression of CRMP2 and Tau rescued the and polarity and that are critical downstream of the pathway in the establishment of neuronal polarity. CRMP2 and Tau are known to roles in expression of CRMP2 and Tau rescued the and polarity their single the was and that have a in axon formation. CRMP2 and Tau mRNAs a 5′-TOP and their translation was controlled via the 5′-TOP and Taken together, these that the activation of p70S6K in the axon of developing neurons to the local translation of CRMP2 and Tau by the maintenance and of axon mRNAs for proteins translation is controlled by mTOR have a 5′-TOP (10Ruvinsky I. Meyuhas O. Trends Biochem. Sci. 2006; 31: 342-348Abstract Full Text Full Text PDF PubMed Scopus (594) Google Scholar, M. M. Biochem. 2006; PubMed Scopus Google Scholar). The of our that the CRMP2 is a 5′-TOP (Fig. The multiple is highly in that the translation of CRMP2 is important for its We also that the Tau a tract its (Fig. translation of CRMP2 and Tau mRNAs via 5′-TOP in the axonal accumulation of CRMP2 and Tau proteins (Fig. and and and In it is well that the Tau is to the of the axon via its axonal which be in the accumulation of Tau proteins in the axon J. L. I. Neuron. Full Text PDF PubMed Scopus Google Scholar, S. G. L. I. J. Neurosci. PubMed Google Scholar). In addition, H. A. Kaibuchi K. J. PubMed Scopus Google Scholar) reported that to CRMP2 and it to the axon. These mechanisms for the axonal of CRMP2 and Tau proteins regulate the specification and maintenance of a single axon. p70S6K was first reported as a downstream effector in the mTOR-governed translation of 5′-TOP mRNAs S. G. J. PubMed Scopus Google Scholar). and that p70S6K is sufficient for the regulation of 5′-TOP mRNAs H. E. M. G. M. J. Meyuhas O. Biol. PubMed Scopus Google Scholar, M. M. J. M. S. G. Biol. 2004; PubMed Scopus Google Scholar), the that and the translation of 5′-TOP mRNAs. In hippocampal neurons, the activation of p70S6K was for axon specification, and rescued the polarity 1 and 2). increased the translation of CRMP2 and Tau even in the and and the translation of and We further that the translation of 5′-TOP O. J. Biochem. PubMed Scopus Google Scholar) was also by via its 5′-TOP 4). These that p70S6K controls the translation of CRMP2 and Tau mRNAs via the 5′-TOP sequences in developing hippocampal (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar) recently reported that the sclerosis proteins, which are of the axon formation. They identified the SAD increased in to their we that the expression of SAD kinases by rapamycin (Fig. 4). (8Choi Y.J. Di Nardo A. Kramvis I. Meikle L. Kwiatkowski D.J. Sahin M. He X. Genes Dev. 2008; 22: 2485-2495Crossref PubMed Scopus (200) Google Scholar) also reported that the expression of SAD kinases are by rapamycin that mTOR activity is for the expression of SAD kinases in developing cultured hippocampal the expression of SAD kinases in the CA-S6K-expressing neurons (Fig. the that protein of SAD kinases be by p70S6K of translation protein Thus, the regulation of SAD kinases must be We SAD kinases to be in the axon, and and SAD kinases showed of the polarity indicating that SAD kinases are important for the axon formation. (9Li Y.H. Werner H. Püschel A.W. J. Biol. Chem. 2008; 283: 33784-33792Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar) also reported the regulation of neuronal polarity by the pathway. In their was identified as a critical polarity protein regulated by mTOR-dependent protein synthesis. We also the mTOR of Rap1 expression and 4). expression increased the of in the and hippocampal neurons, it was CRMP2 Tau and They also the of in axon formation as a downstream effector of mTOR. We that neurons form a that is in the neuronal polarity formation. However, and rapamycin (Fig. 1), by a of including that of overexpression of which that been by multiple axons. However, p70S6K was necessary and sufficient for mTOR-controlled axon formation, as Thus, p70S6K is a effector of the mTOR pathway in the development of neuronal polarity. In mTOR-p70S6K-governed protein synthesis is for the development of neuronal polarity. The activation of the mTOR pathway in the axon the local translation of several polarity genes, CRMP2 and CRMP2 and Tau specifically in the axon via local to the specification, formation, and maintenance of a single axon. Thus, this study the mechanism of mTOR-controlled axon formation and the establishment of neuronal polarity.