Journal
BIOCHEMICAL JOURNAL
Volume 449, Issue -, Pages 39-49Publisher
PORTLAND PRESS LTD
DOI: 10.1042/BJ20121034
Keywords
1-8-14 motif; calcium signalling; calmodulin; inositol 1,4,5-trisphosphate receptor; myosin light chain kinase (MLCK)
Categories
Funding
- Wellcome Trust [085295]
- Biotechnology and Biological Sciences Research Council [BB/H009736/1]
- Engineering and Physical Sciences Research Council
- BBSRC [BB/H009736/1] Funding Source: UKRI
- Biotechnology and Biological Sciences Research Council [BB/H009736/1] Funding Source: researchfish
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Binding of IP3 (inositol 1,4,5-trisphosphate) to the IP3-binding core (residues 224-604) of IP(3)Rs (IP3 receptors) initiates opening of these ubiquitous intracellular Ca2+ channels. The mechanisms are unresolved, but require conformational changes to pass through the suppressor domain (residues 1-223). A calmodulin-binding peptide derived from myosin light chain kinase uncouples these events. We identified a similar conserved 1-8-14 calmodulin-binding motif within the suppressor domain of IP(3)R1 and, using peptides and mutaeenesis, we demonstrate that it is essential for IP3R activation, whether assessed by IP3-evoked Ca2+ release or patch-clamp recoding of nuclear IP3R. Mimetic peptides specifically inhibit activation of IP3R by uncoupling the IP3-binding core from the suppressor domain. Mutations of key hydrophobic residues within the endogenous 1-8-14 motif mimic the peptides. Our results show that an endogenous 1-8-14 motif mediates conformational changes that are essential for IP3R activation. The inhibitory effects of calmodulin and related proteins may result from disruption of this essential interaction.
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