PMID- 32622801 OWN - NLM STAT- MEDLINE DCOM- 20210113 LR - 20220223 IS - 1096-0007 (Electronic) IS - 0014-4835 (Print) IS - 0014-4835 (Linking) VI - 197 DP - 2020 Aug TI - mTORC1 and mTORC2 expression in inner retinal neurons and glial cells. PG - 108131 LID - S0014-4835(20)30389-4 [pii] LID - 10.1016/j.exer.2020.108131 [doi] AB - The retina is one of the most metabolically active tissues, yet the processes that control retinal metabolism remains poorly understood. The mTOR complex (mTORC) that drives protein and lipid biogenesis and autophagy has been studied extensively in regards to retinal development and responses to optic nerve injury but the processes that regulate homeostasis in the adult retina have not been determined. We previously demonstrated that normal adult retina has high rates of protein synthesis compared to skeletal muscle, associated with high levels of mechanistic target of rapamycin (mTOR), a kinase that forms multi-subunit complexes that sense and integrate diverse environmental cues to control cell and tissue physiology. This study was undertaken to: 1) quantify expression of mTOR complex 1 (mTORC1)- and mTORC2-specific partner proteins in normal adult rat retina, brain and liver; and 2) to localize these components in normal human, rat, and mouse retinas. Immunoblotting and immunoprecipitation studies revealed greater expression of raptor (exclusive to mTORC1) and rictor (exclusive for mTORC2) in normal rat retina relative to liver or brain, as well as the activating mTORC components, pSIN1 and pPRAS40. By contrast, liver exhibits greater amounts of the mTORC inhibitor, DEPTOR. Immunolocalization studies for all three species showed that mTOR, raptor, and rictor, as well as most other known components of mTORC1 and mTORC2, were primarily localized in the inner retina with mTORC1 primarily in retinal ganglion cells (RGCs) and mTORC2 primarily in glial cells. In addition, phosphorylated ribosomal protein S6, a direct target of the mTORC1 substrate ribosomal protein S6 kinase beta-1 (S6K1), was readily detectable in RGCs, indicating active mTORC1 signaling, and was preserved in human donor eyes. Collectively, this study demonstrates that the inner retina expresses high levels of mTORC1 and mTORC2 and possesses active mTORC1 signaling that may provide cell- and tissue-specific regulation of homeostatic activity. These findings help to define the physiology of the inner retina, which is key for understanding the pathophysiology of optic neuropathies, glaucoma and diabetic retinopathy. CI - Copyright (c) 2020 Elsevier Ltd. All rights reserved. FAU - Losiewicz, Mandy K AU - Losiewicz MK AD - Ophthalmology & Visual Sciences, United States. FAU - Elghazi, Lynda AU - Elghazi L AD - Ophthalmology & Visual Sciences, United States. FAU - Fingar, Diane C AU - Fingar DC AD - Biological Chemistry, United States. FAU - Rajala, Raju V S AU - Rajala RVS AD - Departments of Ophthalmology and Physiology, University of Oklahoma Health Sciences Center, United States. FAU - Lentz, Stephen I AU - Lentz SI AD - Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, United States. FAU - Fort, Patrice E AU - Fort PE AD - Ophthalmology & Visual Sciences, United States; Molecular and Integrative Physiology, University of Michigan Medical School, United States. FAU - Abcouwer, Steven F AU - Abcouwer SF AD - Ophthalmology & Visual Sciences, United States. FAU - Gardner, Thomas W AU - Gardner TW AD - Ophthalmology & Visual Sciences, United States; Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, United States; Molecular and Integrative Physiology, University of Michigan Medical School, United States. Electronic address: tomwgard@umich.edu. LA - eng GR - P30 DK092926/DK/NIDDK NIH HHS/United States GR - R01 EY020582/EY/NEI NIH HHS/United States GR - R24 DK082841/DK/NIDDK NIH HHS/United States GR - R01 DK100722/DK/NIDDK NIH HHS/United States GR - R01 DK107535/DK/NIDDK NIH HHS/United States GR - P30 DK020572/DK/NIDDK NIH HHS/United States GR - P30 EY007003/EY/NEI NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural PT - Research Support, Non-U.S. Gov't DEP - 20200702 PL - England TA - Exp Eye Res JT - Experimental eye research JID - 0370707 RN - 63231-63-0 (RNA) RN - EC 2.7.11.1 (Mechanistic Target of Rapamycin Complex 1) RN - EC 2.7.11.1 (Mechanistic Target of Rapamycin Complex 2) SB - IM MH - Animals MH - Disease Models, Animal MH - *Gene Expression Regulation MH - Humans MH - Immunoblotting MH - Male MH - Mechanistic Target of Rapamycin Complex 1/biosynthesis/*genetics MH - Mechanistic Target of Rapamycin Complex 2/biosynthesis/*genetics MH - Mice MH - Mice, Inbred C57BL MH - RNA/*genetics/metabolism MH - Rats MH - Rats, Sprague-Dawley MH - Retinal Diseases/*genetics/metabolism/pathology MH - Retinal Ganglion Cells/*metabolism/pathology MH - Signal Transduction PMC - PMC7484061 MID - NIHMS1609772 OTO - NOTNLM OT - Protein synthesis OT - Raptor OT - Retina OT - Retinal ganglion cells OT - Rictor OT - mTORC EDAT- 2020/07/06 06:00 MHDA- 2021/01/14 06:00 PMCR- 2021/08/01 CRDT- 2020/07/06 06:00 PHST- 2020/04/20 00:00 [received] PHST- 2020/06/09 00:00 [revised] PHST- 2020/06/24 00:00 [accepted] PHST- 2020/07/06 06:00 [pubmed] PHST- 2021/01/14 06:00 [medline] PHST- 2020/07/06 06:00 [entrez] PHST- 2021/08/01 00:00 [pmc-release] AID - S0014-4835(20)30389-4 [pii] AID - 10.1016/j.exer.2020.108131 [doi] PST - ppublish SO - Exp Eye Res. 2020 Aug;197:108131. doi: 10.1016/j.exer.2020.108131. Epub 2020 Jul 2.