Expression and distribution of mTOR, p70S6K, 4E-BP1, and their phosphorylated counterparts in rat dorsal root ganglion and spinal cord dorsal horn.
Mammalian target of rapamycin (mTOR) controls protein translation and has an important role in the mechanism of pain hypersensitivity under persistent pain conditions. However, its expression and localization in pain-related regions of the nervous system is not completely understood. Here, we examined the expression and distribution of mTOR, eukaryotic initiation factor 4E-binding protein1/2 (4E-BP1/2), p70 ribosomal S6 protein kinase (p70S6K), and their phosphorylated (active) counterparts in two major pain-related regions, the dorsal root ganglion (DRG) and spinal cord dorsal horn. Reverse transcriptase-polymerase chain reaction showed that mTOR, 4E-BP1, and p70S6K mRNA are expressed in the DRG and dorsal horn. Western blot analysis further confirmed the existence of their protein products in these two regions, but expression of their phosphorylated counterparts was very low in dorsal horn and was not detected in the DRG. Immunohistochemistry revealed mTOR and p70S6K in the DRG neurons. Quantitative analysis showed that approximately 26.1% (+/- 3.2%) of DRG neurons were positive for mTOR and 19.1% (+/- 1.9%) were positive for p70S6K. Most of these neurons were small-less than 600 microm(2) in cross-sectional area-and some co-labeled with substance P or isolectin B4. Surprisingly, 4E-BP1 was observed only in the DRG satellite glial cells. In the dorsal horn, mTOR, p70S6K, and 4E-BP1 were detected in neurons, but not in astrocytes or microglia. They were distributed in the whole dorsal horn, especially in the superficial dorsal horn. Immunostaining for their phosphorylated counterparts was very low or undetectable in DRG and dorsal horn. Behavioral study showed that intrathecal mTOR inhibitor, rapamycin, did not affect acute nocicepetive transmission. The results indicate that although mTOR, p70S6K, and 4E-BP1 are highly expressed in the DRG and dorsal horn, their activate forms are very low in both regions under normal conditions. Our findings support the view that mTOR and its downstream effectors do not play a key role in acute pain.
Xu
Ji-Tain
JT
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Zhao
Xiuli
X
Yaster
Myron
M
Tao
Yuan-Xiang
YX
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D005727:Ganglia, Spinal / Q000378:metabolism*; D015870:Gene Expression; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D010146:Pain / Q000378:metabolism*; D010750:Phosphoproteins / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation; D020671:Posterior Horn Cells / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000096:biosynthesis* / Q000235:genetics; D058570:TOR Serine-Threonine Kinases
D002352:Carrier Proteins; C499526:Eif4ebp1 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; C546845:mTOR protein, rat; D017346:Protein Serine-Threonine Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases
Neuroscience. 2009 Jun 2;160(4):847-57
19303429
PLoS One. 2008 Apr 09;3(4):e1961
18398477
J Neurosci. 2009 Nov 25;29(47):15017-27
19940197
Biochim Biophys Acta. 2008 Jan;1784(1):116-32
17913600
Neuroscience. 2004;123(4):1045-51
14751295
Biochem J. 2007 Apr 15;403(2):217-34
17376031
Proteomics. 2009 Mar;9(5):1241-53
19206110
J Neurosci. 2007 Dec 19;27(51):13958-67
18094233
Mol Pain. 2009 Jun 07;5:27
19500426
J Neurosci. 2004 Nov 3;24(44):9760-9
15525761
Mol Pain. 2008 Oct 14;4:45
18851757
FEBS J. 2005 Aug;272(16):4211-20
16098202
Eur J Pain. 2010 Jan;14(1):49.e1-11
19345595
Mol Pain. 2008 Dec 30;4:67
19116032
J Pain. 2009 Sep;10(9):895-926
19712899
Naunyn Schmiedebergs Arch Pharmacol. 2009 Nov;380(5):459-63
19756519
Eur J Neurosci. 2009 Jun;29(12):2253-63
19490023
J Neurosci. 2009 Mar 11;29(10):3206-19
19279258
Genes Dev. 2004 Aug 15;18(16):1926-45
15314020
J Neurosci. 2004 Nov 10;24(45):10211-22
15537893
Mol Neurobiol. 2006 Dec;34(3):205-19
17308353
Brain Behav Immun. 2007 Jul;21(5):592-8
17222529
Cancer Res. 2007 Aug 15;67(16):7551-5
17699757