July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
The Contribution of Endoplasmic Reticulum Calcium Deficiency to Mistrafficking of Cone Outer Segment Proteins in CNG Channel Deficiency
Author Affiliations & Notes
  • Hongwei Ma
    The Department of Cell Biology, Univ of Oklahoma Health Sci Ctr, Oklahoma City, Oklahoma, United States
  • Fan Yang
    The Department of Cell Biology, Univ of Oklahoma Health Sci Ctr, Oklahoma City, Oklahoma, United States
  • Michael Robert Butler
    The Department of Cell Biology, Univ of Oklahoma Health Sci Ctr, Oklahoma City, Oklahoma, United States
  • Jacob Rapp
    The Department of Cell Biology, Univ of Oklahoma Health Sci Ctr, Oklahoma City, Oklahoma, United States
  • Yun-Zheng Le
    The Department of Physiology, Univ of Oklahoma Health Sci Ctr, Oklahoma City, Oklahoma, United States
  • Katsuhiko Mikoshiba
    RIKEN Brain Science Institute, Japan
  • Martin Biel
    Center for Integrated Protein Science Munich (CIPSM) and Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
  • Stylianos Michalakis
    Center for Integrated Protein Science Munich (CIPSM) and Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
  • Xi-Qin Ding
    The Department of Cell Biology, Univ of Oklahoma Health Sci Ctr, Oklahoma City, Oklahoma, United States
  • Footnotes
    Commercial Relationships   Hongwei Ma, None; Fan Yang, None; Michael Butler, None; Jacob Rapp, None; Yun-Zheng Le, None; Katsuhiko Mikoshiba, None; Martin Biel, None; Stylianos Michalakis, None; Xi-Qin Ding, None
  • Footnotes
    Support  This work was supported by grants from the National Eye Institute (P30EY021725 and R01EY027754), the Oklahoma Center for the Advancement of Science and Technology, and the Deutsche Forschungsgemeinschaft (DFG).
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 4207. doi:
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      Hongwei Ma, Fan Yang, Michael Robert Butler, Jacob Rapp, Yun-Zheng Le, Katsuhiko Mikoshiba, Martin Biel, Stylianos Michalakis, Xi-Qin Ding; The Contribution of Endoplasmic Reticulum Calcium Deficiency to Mistrafficking of Cone Outer Segment Proteins in CNG Channel Deficiency. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4207.

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

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Abstract

Purpose : The photoreceptor cyclic nucleotide-gated (CNG) channel plays a pivotal role in phototransduction and cellular calcium homeostasis. Mutations in cone CNG channel are associated with achromatopsia and cone dystrophies. We previously showed that CNG channel deficiency leads to endoplasmic reticulum (ER) stress-associated cone death and cone opsin mistrafficking. We also demonstrated enhanced expression/activity of the ER calcium releasing channels inositol 1,4,5-trisphosphate receptor 1 (IP3R1) and ryanodine receptor 2 (RyR2) in CNG channel-deficient mice. This work investigated the potential mechanism of cone protein mistrafficking associated with ER calcium regulation in CNG channel deficiency.

Methods : Cnga3-/- mice with cone-specific deletions of Ryr2 (encoding RyR2) or Itpr1 (encoding IP3R1) were generated by cross mating. Cellular localization of cone outer segment proteins M-opsin, S-opsin and phosphodiesterase 6C (PDE6C) was examined by immunofluorescence labeling, confocal microscopy and ImageJ analysis. Cone survival was evaluated by peanut agglutinin (PNA) labeling. Expression of the ER chaperone proteins was evaluated by immunoblotting.

Results : Deletion of Ryr2 or Itpr1 improved outer segment (OS) localization of cone proteins in Cnga3-/- mice. One-month-old Cnga3-/- mice showed 27% of M-opsin, 56% of S-opsin, and 50% of PDE6C localized to the OS. Cnga3-/-/Ryr2fl/fl/HrgpCre mice at the same age showed about 59% of M-opsin, 71% of S-opsin, and 70% of PDE6C localized to the OS, and Cnga3-/-/Itpr1fl/fl/HrgpCre mice showed about 78% of S-opsin and 67% of PDE6C localized to the OS. Consistent with improved cone protein trafficking, cone density also significantly increased in Cnga3-/- mice with deletion of Itpr1 or Ryr2. PNA positive cells increased by approximately 28% in ventral retinas of 2-month-old Cnga3-/-/Ryr2fl/fl/HrgpCre mice, compared with Cnga3-/- mice. Expression of the ER chaperone proteins Grp78/BiP and calreticulin was not affected by deletion of the ER calcium channels.

Conclusions : Deletion of Ryr2 or Itpr1 improves outer segment localization of cone proteins in CNG deficiency, suggesting a contribution of ER calcium deficiency to mistrafficking of cone outer segment proteins. This regulation appears to be mediated by an ER chaperone-independent mechanism.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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