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mTORC1 regulates high levels of protein synthesis in retinal ganglion cells of adult mice

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Patrice E. Fort, Mandy K. Losiewicz, Lynda Elghazi, Dejuan Kong, Corentin Cras-Méneur, Diane C. Fingar, Scot R. Kimball, Raju V.S. Rajala, Alexander J. Smith, Robin R. Ali, Steven F. Abcouwer, Thomas W. Gardner

Original languageEnglish
Article number101944
JournalJournal of Biological Chemistry
Volume298
Issue number6
DOIs
Published1 Jun 2022

Bibliographical note

Funding Information: Funding and additional information—This work was supported by the National Institutes of Health (NIH) grants R01EY031961 (to S. F. A. and P. E. F.), R01EY020582 (to S. F. A. and T. W. G.), R01EY020823 (to S. F. A.), R01EY029349 (to S. F. A.), R24-DK-082841 (to S. F. A., P. E. F., and T. W. G.), R01DK100722 (to D. C. F.), DK15658 (to S. R. K.); the Juvenile Diabetes Research Foundation Center of Excellence at the University of Michigan (to T. W. G. and P. E. F.); and Research to Prevent Blindness (to T. W. G.), NIH P30EY007003 (Core Grant for Vision Research at the University of Michigan), and NIH P30DK020572 (Michigan Diabetes Research Center). Publisher Copyright: © 2022 THE AUTHORS.

King's Authors

Abstract

Mechanistic target of rapamycin (mTOR) and mTOR complex 1 (mTORC1), linchpins of the nutrient sensing and protein synthesis pathways, are present at relatively high levels in the ganglion cell layer (GCL) and retinal ganglion cells (RGCs) of rodent and human retinas. However, the role of mTORCs in the control of protein synthesis in RGC is unknown. Here, we applied the SUrface SEnsing of Translation (SUnSET) method of nascent protein labeling to localize and quantify protein synthesis in the retinas of adult mice. We also used intravitreal injection of an adeno-associated virus 2 vector encoding Cre recombinase in the eyes of mtor- or rptor-floxed mice to conditionally knockout either both mTORCs or only mTORC1, respectively, in cells within the GCL. A novel vector encoding an inactive Cre mutant (CreΔC) served as control. We found that retinal protein synthesis was highest in the GCL, particularly in RGC. Negation of both complexes or only mTORC1 significantly reduced protein synthesis in RGC. In addition, loss of mTORC1 function caused a significant reduction in the pan-RGC marker, RNA-binding protein with multiple splicing, with little decrease of the total number of cells in the RGC layer, even at 25 weeks after adeno-associated virus-Cre injection. These findings reveal that mTORC1 signaling is necessary for maintaining the high rate of protein synthesis in RGCs of adult rodents, but it may not be essential to maintain RGC viability. These findings may also be relevant to understanding the pathophysiology of RGC disorders, including glaucoma, diabetic retinopathy, and optic neuropathies.

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