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CLIC-2 modulates cardiac ryanodine receptor Ca2+ release channels
Philip G Board1, Marjorie Coggan, Sarah Watson
1Division of Molecular Bioscience, John Curtin School of Medical Research, The Australian National University, P.O. Box 334, Canberra, ACT 2601, Australia. philip.board@anu.edu.au
Summary
The newly identified CLIC-2 protein, similar to glutathione transferases, inhibits calcium release channels in heart and skeletal muscle. This suggests CLIC-2 may regulate calcium release from cellular stores.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Physiology
Background:
- CLIC-2 is a recently identified protein with sequence similarity to CLIC-1 and glutathione transferases (GSTO).
- Its structural and functional properties remain largely uncharacterized.
- CLIC-2 shares sequence motifs with glutaredoxins but exhibits an atypical enzyme activity profile.
Purpose of the Study:
- To investigate the biochemical and functional characteristics of the CLIC-2 protein.
- To determine the structural family and enzymatic activity of CLIC-2.
- To elucidate the role of CLIC-2 in regulating calcium (Ca2+) release channels, particularly cardiac ryanodine receptors (RyR).
Main Methods:
- Sequence alignment and homology modeling based on CLIC-1 crystal structure.
- Enzyme activity assays to assess thiol transferase and glutathione peroxidase activity.
- Functional studies using lipid bilayers and cardiac sarcoplasmic reticulum vesicles to examine CLIC-2's effect on Ca2+ release channels.
Main Results:
- CLIC-2 belongs to the GST structural family but exists as a monomer.
- No significant thiol transferase activity was detected, but low glutathione peroxidase activity was observed.
- CLIC-2 widely distributed in tissues, including heart and skeletal muscle.
- CLIC-2 inhibited cardiac ryanodine receptor Ca2+ release channels and Ca2+ release from sarcoplasmic reticulum vesicles.
- Inhibition was reversible upon removal of CLIC-2 or addition of an anti-CLIC-2 antibody.
Conclusions:
- CLIC-2 exhibits unique biochemical properties distinct from typical GSTs and glutaredoxins.
- CLIC-2 plays a role in regulating Ca2+ release channels, particularly in cardiac muscle.
- A potential physiological function of CLIC-2 is to limit Ca2+ release from intracellular stores.