June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
A crosstalk between mTORC1 and mTORC2 is required for full retinal ganglion cell regeneration mediated by insulin
Author Affiliations & Notes
  • Sana El Hajji
    Department of Neuroscience, Universite de Montreal Faculte de Medecine, Montreal, Quebec, Canada
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
  • Yukihiro Shiga
    Department of Neuroscience, Universite de Montreal Faculte de Medecine, Montreal, Quebec, Canada
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
  • Nicolas Belforte
    Department of Neuroscience, Universite de Montreal Faculte de Medecine, Montreal, Quebec, Canada
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
  • Yves Carpentier Solorio
    Department of Neuroscience, Universite de Montreal Faculte de Medecine, Montreal, Quebec, Canada
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
  • Olivier Tastet
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
  • Philippe D'Onofrio
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
  • Florence Dotigny
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
  • Alexandre Prat
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
    Department of Neuroscience, Universite de Montreal Faculte de Medecine, Montreal, Quebec, Canada
  • Brad Fortune
    Legacy Devers Eye Institute at Legacy Good Samaritan Medical Center, Portland, Oregon, United States
  • Adriana Di Polo
    Centre Hospitalier de l'Universite de Montreal Centre de Recherche, Montreal, Quebec, Canada
    Department of Neuroscience, Universite de Montreal Faculte de Medecine, Montreal, Quebec, Canada
  • Footnotes
    Commercial Relationships   Sana El Hajji None; Yukihiro Shiga None; Nicolas Belforte None; Yves Carpentier Solorio None; Olivier Tastet None; Philippe D'Onofrio None; Florence Dotigny None; Alexandre Prat None; Brad Fortune None; Adriana Di Polo None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 2839. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Sana El Hajji, Yukihiro Shiga, Nicolas Belforte, Yves Carpentier Solorio, Olivier Tastet, Philippe D'Onofrio, Florence Dotigny, Alexandre Prat, Brad Fortune, Adriana Di Polo; A crosstalk between mTORC1 and mTORC2 is required for full retinal ganglion cell regeneration mediated by insulin. Invest. Ophthalmol. Vis. Sci. 2023;64(8):2839.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract

Purpose : We previously showed that insulin promotes retinal ganglion cell (RGC) dendrite regrowth after optic nerve damage. Insulin is known to activate the mammalian target of rapamycin complexes 1 and 2 (mTORC1, mTORC2), but their specific roles in RGC regeneration are not well understood. Here, we investigated the molecular pathways downstream of mTORC1/2 involved in insulin-mediated restoration of RGC dendritic structure and connectivity.

Methods : Ocular hypertension (OHT) was induced by injection of magnetic microbeads in Thy1-YFP mice and daily insulin eye drops started two weeks later, a time when there is dendritic retraction and synapse loss. Synaptic regeneration was assessed by quantification of AAV-mediated expression of the post-synaptic marker PSD95 on RGC dendrites and co-localization with VGlut1 in bipolar cell axon terminals. The role of insulin downstream effectors was assessed by loss-of-function experiments using siRNAs against: i) the mTORC1 targets p70S6 kinase (S6K) and 4EBP1, which are both important in the control of protein translation initiation, and ii) SIN1, a regulator of mTORC2 activity. Quantification of RGC-specific protein levels and phosphorylation was carried out by flow cytometry.

Results : Insulin treatment promoted substantial dendritic regeneration accompanied by a profound restoration of post- and pre-synaptic connectivity in conditions of OHT stress (n=6 mice/group, ANOVA, p<0.001). siRNA-based knockdown of mTORC1 targets showed that lack of S6K impaired insulin-mediated regeneration, while 4EBP1 silencing had no effect. Intriguingly, S6K increased mTORC2 activity through phosphorylation of SIN1, thus enhancing insulin-mediated RGC dendrite regeneration. Consistent with this, SIN1 knockdown completely abolished insulin-mediated RGC regeneration during OHT (n=6 mice/group, ANOVA, p<0.0001). Furthermore, SIN1 silencing decreased the phosphorylation of Akt, a key mTORC2 target, at residues T308 and S473 (n=5 mice/group, ANOVA, p<0.001).

Conclusions : This study demonstrates that mTORC1 and mTORC2 work together, rather than independently, to promote insulin-mediated RGC regeneration during OHT damage. Specifically, our data show that SIN1 serves as a key molecular link between mTORC1 and mTORC2 to activate the signaling pathways required to restore RGC connectivity.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×