June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Interphotoreceptor matrix proteoglycans IMPG1 and IMPG2 undergoes intramolecular proteolysis and reveal localization interdependency
Author Affiliations & Notes
  • EZEQUIEL M SALIDO
    Biochemistry, and Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
  • Chloe Coulter
    Biochemistry, and Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
  • Benjamin Mitchell
    Biochemistry, and Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
  • Footnotes
    Commercial Relationships   EZEQUIEL SALIDO None; Chloe Coulter None; Benjamin Mitchell None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 1796 – F0345. doi:
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      EZEQUIEL M SALIDO, Chloe Coulter, Benjamin Mitchell; Interphotoreceptor matrix proteoglycans IMPG1 and IMPG2 undergoes intramolecular proteolysis and reveal localization interdependency. Invest. Ophthalmol. Vis. Sci. 2022;63(7):1796 – F0345.

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

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Abstract

Purpose : The interphotoreceptor matrix (IPM) is a specialized extracellular matrix that surrounds the photoreceptors inner and outer segments. Two major constitutes of the IPM are the interphotoreceptor matrix proteoglycan 1 and 2 (IMPG1 and IMPG2). Both proteoglycans possess SEA domains (Sperm protein, Enterokinase and Agrin) which are linked to self-cleave intramolecular proteolysis in proteoglycans. Mutations in the SEA domains of IMPG1 and IMPG2 are associated with vision loss. This work studies the possible proteolysis of IMPG1 and IMPG2 and its relevance to vision physiology

Methods : We used protein alignment computational tools, and classical Wester blot and immunohistochemistry techniques

Results : The amino acid sequence alignment of IMPG1 and IMPG2 against established proteolytic sequences predicted that one of the two SEA domains on both proteins are likely to undergo proteolysis. Western blot analysis of IMPG1 confirmed protein proteolysis independently of IMPG2 presence. On the other hand, western blot and immunohistochemical analysis confirmed IMPG2 proteolysis involving the generation of two IMPG2 subunits, a membrane attached and a free extracellular peptide. These experiments revealed that the extracellular portion of IMPG2 migrates from the IPM inner segment to the IPM outer segment by a mechanism dependent on IMPG1.

Conclusions : Overall, this work demonstrates that IMPG1 and IMPG2 proteolyzed as part of their maturation process and revealed the IPM outer segment localization of the extracellular portion of IMPG2.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

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