The amino-terminal disease hotspot of ryanodine receptors forms a cytoplasmic vestibule.
Many physiological events require transient increases in cytosolic Ca(2+) concentrations. Ryanodine receptors (RyRs) are ion channels that govern the release of Ca(2+) from the endoplasmic and sarcoplasmic reticulum. Mutations in RyRs can lead to severe genetic conditions that affect both cardiac and skeletal muscle, but locating the mutated residues in the full-length channel structure has been difficult. Here we show the 2.5 Å resolution crystal structure of a region spanning three domains of RyR type 1 (RyR1), encompassing amino acid residues 1-559. The domains interact with each other through a predominantly hydrophilic interface. Docking in RyR1 electron microscopy maps unambiguously places the domains in the cytoplasmic portion of the channel, forming a 240-kDa cytoplasmic vestibule around the four-fold symmetry axis. We pinpoint the exact locations of more than 50 disease-associated mutations in full-length RyR1 and RyR2. The mutations can be classified into three groups: those that destabilize the interfaces between the three amino-terminal domains, disturb the folding of individual domains or affect one of six interfaces with other parts of the receptor. We propose a model whereby the opening of a RyR coincides with allosterically coupled motions within the N-terminal domains. This process can be affected by mutations that target various interfaces within and across subunits. The crystal structure provides a framework to understand the many disease-associated mutations in RyRs that have been studied using functional methods, and will be useful for developing new strategies to modulate RyR function in disease states.
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Ching-Chieh
CC
Tung
Paolo A
PA
Lobo
Lynn
L
Kimlicka
Filip
F
Van Petegem
D000818:Animals; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D017434:Protein Structure, Tertiary; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
D019837:Ryanodine Receptor Calcium Release Channel