Malignant Hyperthermia Associated Mutations in S2-S3 Loop of Type 1 Ryanodine Receptor Calcium Channel Alter Calcium Dependent Inactivation
| Autor: | Timothy W Holford, Angela C. Gomez, Naohiro Yamaguchi |
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| Jazyk: | angličtina |
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| Zdroj: | Biophysical Journal. (2):110a |
| ISSN: | 0006-3495 4081-4092 |
| DOI: | 10.1016/j.bpj.2013.11.674 |
| Popis: | Skeletal and cardiac ryanodine receptors (RyRs) are ∼65% similar in their primary sequences, though differences in their regulation by physiological molecules have been observed. Skeletal RyR (RyR1) is inhibited by millimolar Ca2+ with ∼10 fold higher affinity than cardiac isoform (RyR2). Using RyR1/RyR2 chimera channels and [3H]ryanodine binding measurements, we found that two distinct regions are involved in isoform-specific Ca2+-dependent inactivation. One region includes two EF hand Ca2+ binding motifs (RyR1 amino acids 4081-4092 and 4116-4127) and the other contains the second transmembrane segment (S2). The results suggest a possible cytoplasmic domain interaction between these two regions (or involving the flanking regions of S2). Human disease associated mutations have been identified in S2-S3 cytoplasmic loop of RyR1. We found that G4733E and R4736W malignant hyperthermia associated mutations reduced affinity for Ca2+ dependent inactivation of the channels by 5-6 fold (IC50: 6.7±0.6 mM (G4733E) and 5.5±0.2 mM (R4736W) vs 1.1±0.1 mM (wild type RyR1)), whereas mutations in S4-S5 cytoplasmic loop (T4825I and H4832Y) reduced affinity by 2-3 fold. We also found that the activities of G4733E- and R4736W-RyR1 mutants are suppressed at 10-100 µM Ca2+, and the suppressions are relieved by 1 mM Mg2+, which was observed in recombinant wild type RyR2 (Chugun et al., (2007) Am. J. Physiol. Cell Physiol.292, C535) but not in wild type RyR1. Taken together, G4733E and R4736W mutations in S2-S3 loop confer RyR2-type Ca2+ dependent inactivation and Mg2+ activation on RyR1. The S2-S3 cytoplasmic loop may play a key role for domain interaction involved in isoform-specific Ca2+-dependent inactivation of RyRs. Supported by NIH (R03AR061030), AHA (10SDG3500001), and NSF (EPS0903795). |
| Databáze: | OpenAIRE |
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