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  • Title: Selective modulation of coupled ryanodine receptors during microdomain activation of calcium/calmodulin-dependent kinase II in the dyadic cleft.
    Author: Dries E, Bito V, Lenaerts I, Antoons G, Sipido KR, Macquaide N.
    Journal: Circ Res; 2013 Nov 08; 113(11):1242-52. PubMed ID: 24081880.
    Abstract:
    RATIONALE: In ventricular myocytes of large mammals with low T-tubule density, a significant number of ryanodine receptors (RyRs) are not coupled to the sarcolemma; cardiac remodeling increases noncoupled RyRs. OBJECTIVE: Our aim was to test the hypothesis that coupled and noncoupled RyRs have distinct microdomain-dependent modulation. METHODS AND RESULTS: We studied single myocytes from pig left ventricle. The T-tubule network was analyzed in 3-dimension (3D) to measure distance to membrane of release sites. The rising phase of the Ca(2+) transient was correlated with proximity to the membrane (confocal imaging, whole-cell voltage-clamp, K5fluo-4 as Ca(2+) indicator). Ca(2+) sparks after stimulation were thus identified as resulting from coupled or noncoupled RyRs. We used high-frequency stimulation as a known activator of Ca(2+)/calmodulin-dependent kinase II. Spark frequency increased significantly more in coupled than in noncoupled RyRs. This specific modulation of coupled RyRs was abolished by the Ca(2+)/calmodulin-dependent kinase II blockers autocamtide-2-related inhibitory peptide and KN-93, but not by KN-92. Colocalization of Ca(2+)/calmodulin-dependent kinase II and RyR was not detectably different for coupled and noncoupled sites, but the F-actin disruptor cytochalasin D prevented the specific modulation of coupled RyRs. NADPH oxidase 2 inhibition by diphenyleneiodonium or apocynin, or global reactive oxygen species scavenging, also prevented coupled RyR modulation. During stimulated Ca(2+) transients, frequency-dependent increase of the rate of Ca(2+) rise was seen in coupled RyR regions only and abolished by autocamtide-2-related inhibitory peptide. After myocardial infarction, selective modulation of coupled RyR was lost. CONCLUSIONS: Coupled RyRs have a distinct modulation by Ca(2+)/calmodulin-dependent kinase II and reactive oxygen species, dependent on an intact cytoskeleton and consistent with a local Ca(2+)/reactive oxygen species microdomain, and subject to modification with disease.
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