1. Loss of SPEG Inhibitory Phosphorylation of Ryanodine Receptor Type-2 Promotes Atrial Fibrillation
- Author
-
Ann P. Quick, Issam Abu-Taha, Dobromir Dobrev, Eleonora Corradini, Xander H.T. Wehrens, Stephan E. Lehnart, Katherina M. Alsina, Oliver Moore, Dennis Uhlenkamp, Hannah M. Campbell, Sören Brandenburg, Tarah A. Word, Markus Kamler, David Y. Chiang, Satadru K. Lahiri, Brian Martin, Albert J. R. Heck, Mohit Hulsurkar, Carlos F. Kramm, Hui-Bin Liu, Sub Biomol.Mass Spectrometry & Proteom., Afd Biomol.Mass Spect. and Proteomics, and Biomolecular Mass Spectrometry and Proteomics
- Subjects
Male ,medicine.medical_specialty ,Diastole ,Medizin ,chemistry.chemical_element ,Muscle Proteins ,030204 cardiovascular system & hematology ,Calcium ,Protein Serine-Threonine Kinases ,Inhibitory postsynaptic potential ,Ryanodine receptor 2 ,Article ,03 medical and health sciences ,Mice ,0302 clinical medicine ,Physiology (medical) ,Internal medicine ,Atrial Fibrillation ,Medicine ,Animals ,Humans ,Calcium Signaling ,Phosphorylation ,Myosin-Light-Chain Kinase ,030304 developmental biology ,Mice, Knockout ,0303 health sciences ,business.industry ,Ryanodine receptor ,Endoplasmic reticulum ,Myocardium ,Atrial fibrillation ,Ryanodine Receptor Calcium Release Channel ,medicine.disease ,musculoskeletal system ,Sarcoplasmic Reticulum ,Endocrinology ,chemistry ,cardiovascular system ,Female ,Cardiology and Cardiovascular Medicine ,business - Abstract
Background: Enhanced diastolic calcium (Ca 2+ ) release through ryanodine receptor type-2 (RyR2) has been implicated in atrial fibrillation (AF) promotion. Diastolic sarcoplasmic reticulum Ca 2+ leak is caused by increased RyR2 phosphorylation by PKA (protein kinase A) or CaMKII (Ca 2+ /calmodulin-dependent kinase-II) phosphorylation, or less dephosphorylation by protein phosphatases. However, considerable controversy remains regarding the molecular mechanisms underlying altered RyR2 function in AF. We thus aimed to determine the role of SPEG (striated muscle preferentially expressed protein kinase), a novel regulator of RyR2 phosphorylation, in AF pathogenesis. Methods: Western blotting was performed with right atrial biopsies from patients with paroxysmal AF. SPEG atrial knockout mice were generated using adeno-associated virus 9. In mice, AF inducibility was determined using intracardiac programmed electric stimulation, and diastolic Ca 2+ leak in atrial cardiomyocytes was assessed using confocal Ca 2+ imaging. Phosphoproteomics studies and Western blotting were used to measure RyR2 phosphorylation. To test the effects of RyR2-S2367 phosphorylation, knockin mice with an inactivated S2367 phosphorylation site (S2367A) and a constitutively activated S2367 residue (S2367D) were generated by using CRISPR-Cas9. Results: Western blotting revealed decreased SPEG protein levels in atrial biopsies from patients with paroxysmal AF in comparison with patients in sinus rhythm. SPEG atrial-specific knockout mice exhibited increased susceptibility to pacing-induced AF by programmed electric stimulation and enhanced Ca 2+ spark frequency in atrial cardiomyocytes with Ca 2+ imaging, establishing a causal role for decreased SPEG in AF pathogenesis. Phosphoproteomics in hearts from SPEG cardiomyocyte knockout mice identified RyR2-S2367 as a novel kinase substrate of SPEG. Western blotting demonstrated that RyR2-S2367 phosphorylation was also decreased in patients with paroxysmal AF. RyR2-S2367A mice exhibited an increased susceptibility to pacing-induced AF, and aberrant atrial sarcoplasmic reticulum Ca 2+ leak, as well. In contrast, RyR2-S2367D mice were resistant to pacing-induced AF. Conclusions: Unlike other kinases (PKA, CaMKII) that increase RyR2 activity, SPEG phosphorylation reduces RyR2-mediated sarcoplasmic reticulum Ca 2+ release. Reduced SPEG levels and RyR2-S2367 phosphorylation typified patients with paroxysmal AF. Studies in S2367 knockin mouse models showed a causal relationship between reduced S2367 phosphorylation and AF susceptibility. Thus, modulating SPEG activity and phosphorylation levels of the novel S2367 site on RyR2 may represent a novel target for AF treatment.
- Published
- 2020