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Developmental truncations of connexin 50 by caspases adaptively regulate gap junctions/hemichannels and protect lens

Ke Wang1, Sumin Gu, Xinye Yin

  • 1State Key Laboratory of Pharmaceutical Biotechnology, College of Life Sciences, Nanjing University, Nanjing 210093, China.

The Journal of Biological Chemistry
|March 16, 2012
PubMed

Insights

Connexin 50 (Cx50) cleavage by caspases during lens development reduces gap junction function. This truncation may protect lens cells from UV-induced oxidative stress, potentially impacting cataract formation.

Area of Science:

  • Ophthalmology
  • Cell Biology
  • Biochemistry

Background:

  • Connexin 50 (Cx50) is crucial for lens transparency and function.
  • Gradual truncation of Cx50 occurs during lens development, and premature cleavage is linked to cataract formation.
  • Caspase-3-like proteases are implicated in Cx50 cleavage during chick lens development.

Purpose of the Study:

  • To identify the specific cleavage sites and proteases responsible for Cx50 truncation during lens development.
  • To investigate the functional consequences of Cx50 truncation on gap junction and hemichannel activity.
  • To explore the role of Cx50 cleavage in cellular protection against oxidative stress.

Main Methods:

  • High-performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-ESI-MS/MS) to map cleavage sites.
  • Protease activity assays to identify responsible caspases (caspase-1 and caspase-3).
  • In vitro studies using UV radiation and caspase inhibitors to assess cleavage and function.

Main Results:

  • Two C-terminal cleavage sites (after Glu-368 and Asp-379) were identified, with caspase-3 and caspase-1 as the responsible proteases, respectively.
  • Caspase activity increased during lens development, correlating with truncated Cx50 accumulation.
  • Caspase-truncated Cx50 exhibited significantly reduced gap junction coupling and hemichannel function.
  • Truncated Cx50 fragments enhanced cell viability against UV radiation compared to full-length Cx50.

Conclusions:

  • Caspase-1 and caspase-3 are the primary proteases cleaving Cx50 at its C terminus during lens development.
  • Cx50 truncation leads to decreased gap junction coupling and hemichannel function.
  • Cx50 cleavage may represent an adaptive mechanism to protect lens cells from oxidative stress during aging.

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