Activated CaMKIIδ translocates to the RyR nanodomain in cardiomyocytes

Bergan-Dahl, Anna; Carlson, Cathrine R.; Laasmaa, Martin; Subramanian, Hariharan; Basson, Adelle; Li, Jia; Hasic, Almira; Lunde, Marianne; Ugland, Hege; Manfra, Ornella; Klussmann, Enno; Bossuyt, Julie; Bers, Donald M.; Nikolaev, Viacheslav O.; Louch, William E.; Shen, Xin

Activated CaMKIIδ translocates to the RyR nanodomain in cardiomyocytes

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Item Type:	Article
Title:	Activated CaMKIIδ translocates to the RyR nanodomain in cardiomyocytes
Creators Name:	Bergan-Dahl, Anna, Carlson, Cathrine R., Laasmaa, Martin, Subramanian, Hariharan, Basson, Adelle, Li, Jia, Hasic, Almira, Lunde, Marianne, Ugland, Hege, Manfra, Ornella, Klussmann, Enno, Bossuyt, Julie, Bers, Donald M., Nikolaev, Viacheslav O., Louch, William E. and Shen, Xin
Abstract:	BACKGROUND: The heartbeat is triggered by the coordinated release of Ca2+ from the ryanodine receptor type-2 (RyR) in cardiomyocytes. Phosphorylation of RyR by Ca2+/calmodulin-dependent kinase IIδ (CaMKIIδ) fine-tunes this process in health, while hyperphosphorylation causes excessive, pathological Ca2+ release. We investigated how CaMKIIδ is spatially recruited and anchored to RyRs to achieve this functional regulation. METHODS: We employed confocal and dSTORM microscopy to investigate the macro- and nanoscale distribution of CaMKIIδ across cardiomyocytes, respectively. We linked positional rearrangement of the kinase during β-adrenergic stimulation (isoproterenol, Iso) to alterations in RyR phosphorylation and function (Ca2+ sparks), and the requirement of the CaMKIIδ anchoring protein AKAP18δ by knockdown/knockout. RESULTS: Confocal microscopy revealed that macroscale CaMKIIδ localization was not markedly altered during Iso treatment, although a narrowing of its distribution around the Z-lines occurred, where the RyR reside. Higher resolution dSTORM imaging confirmed that local mobilization of CaMKIIδ by Iso decreased the distance from Z-lines and RyRs to the nearest CaMKIIδ by 28% and 12%, respectively. Functionally, kinase translocation into the RyR nanodomain was accompanied by increased channel phosphorylation and Ca2+ spark frequency. These actions were dependent on CaMKIIδ activity, since kinase translocation, RyR phosphorylation, and activation were all mimicked by the upstream activator of CaMKIIδ (8-CPT) and prevented by direct CaMKIIδ inhibitors (AIP, N1 peptide). A critical role of AKAP18δ in this mechanism was supported by immunoprecipitation experiments, which showed greater kinase binding to AKAP18δ during Iso stimulation. Furthermore, loss of AKAP18δ by viral-mediated AKAP18δ knockdown or knockout prevented CaMKIIδ translocation to Z-lines. Microtubular disruption also blocked CaMKIIδ translocation. CONCLUSIONS: Collectively, our results indicate that nanoscale movement of CaMKIIδ is closely associated with RyR activation following β-adrenergic stimulation. This translocation depends on an intact microtubular network and kinase binding to AKAP18δ.
Keywords:	Animals, Mice, Rats, Rabbits
Source:	Cardiovascular Research
ISSN:	0008-6363
Publisher:	Oxford University Press
Date:	10 October 2025
Official Publication:	https://doi.org/10.1093/cvr/cvaf187
PubMed:	View item in PubMed

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