Association of FK506 binding proteins with RyR channels - effect of CLIC2 binding on sub-conductance opening and FKBP binding.

Abstract

Ryanodine receptor (RyR) Ca2+ channels are central to striated muscle function and influence signalling in neurons and other cell types. Beneficially low RyR activity and maximum conductance opening may be stabilised when RyRs bind to FK506 binding proteins (FKBPs) and destabilised by FKBP dissociation, with submaximal opening during RyR hyperactivity associated with myopathies and neurological disorders. However, the correlation with submaximal opening is debated and quantitative evidence is lacking. Here, we have measured altered FKBP binding to RyRs and submaximal activity with addition of wild-type (WT) CLIC2, an inhibitory RyR ligand, or its H101Q mutant that hyperactivates RyRs, which probably causes cardiac and intellectual abnormalities. The proportion of sub-conductance opening increases with WT and H101Q CLIC2 and is correlated with reduced FKBP-RyR association. The sub-conductance opening reduces RyR currents in the presence of WT CLIC2. In contrast, sub-conductance openings contribute to excess RyR 'leak' with H101Q CLIC2. There are significant FKBP and RyR isoform-specific actions of CLIC2, rapamycin and FK506 on FKBP-RyR association. The results show that FKBPs do influence RyR gating and would contribute to excess Ca2+ release in this CLIC2 RyR channelopathy.

• Authors: Spencer J Richardson, Gregory A Steele, Esther M Gallant, Alexander Lam, Charles E Schwartz, Philip G Board, Marco G Casarotto, Nicole A Beard, Angela F Dulhunty
• Journal: Journal of cell science (J Cell Sci) Vol. 130 Issue 20 Pg. 3588-3600 (Oct 15 2017) ISSN: 1477-9137 [Electronic] England
• PMID: 28851804 (Publication Type: Journal Article)
• Copyright: © 2017. Published by The Company of Biologists Ltd.

Chemical References

• Chloride Channels
• Ryanodine Receptor Calcium Release Channel
• Tacrolimus Binding Proteins

Topics

• Animals
• Chloride Channels (metabolism)
• Ion Channel Gating
• Membrane Potentials
• Mutation, Missense
• Protein Binding
• Rabbits
• Ryanodine Receptor Calcium Release Channel (metabolism)
• Sheep, Domestic
• Tacrolimus Binding Proteins (metabolism)