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Structural order in Pannexin 1 cytoplasmic domains
Gaelle Spagnol1, Paul L Sorgen1, David C Spray2
1University of Nebraska Medical Center; Department of Biochemistry and Molecular Biology; Omaha, NE USA.
Channels (Austin, Tex.)
|April 23, 2014
Summary
Pannexin 1 channels, crucial in the central nervous system, exhibit significant secondary structure in their cytoplasmic domains. These structural changes in the carboxyl terminal domain are key to channel opening during apoptosis.
Area of Science:
- Molecular Biology
- Cell Biology
- Neuroscience
Background:
- Pannexin 1 forms hexameric channels permeable to ions and metabolites, with widespread expression.
- While not forming intercellular channels, Pannexin 1 shares structural and functional similarities with connexins, particularly in its carboxyl terminal (CT) domain's role in gating.
Purpose of the Study:
- To characterize the secondary structure of mouse Pannexin 1 cytoplasmic domains.
- To compare Pannexin 1 structures with those of connexins.
- To elucidate the mechanism of Pannexin 1 channel opening during apoptosis.
Main Methods:
- Computational structural prediction tools.
- Circular dichroism spectroscopy.
- Nuclear Magnetic Resonance (NMR) spectroscopy.
- In vitro caspase cleavage assays.
Main Results:
- Pannexin 1 cytosolic regions contain substantial secondary structure (~50%), predominantly alpha-helical, unlike connexins.
- A potential membrane-interacting region was identified in the CT domain, upstream of the caspase cleavage site.
- Alpha-helical content increased in detergent micelles, indicating membrane association.
- Caspase-3 cleavage of the Pannexin 1 CT domain was confirmed in vitro.
Conclusions:
- Pannexin 1 cytoplasmic domains possess significant alpha-helical content.
- Structural changes in the CT domain, including membrane association and caspase cleavage, are proposed to mediate channel opening during apoptosis.
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