RYR2 and atrial fibrillation: In the third study, we immunoprecipitated RyR2 and identified a number of protein phosphatases using MS including a novel RyR2 interactor, protein phosphatase 1 (PP1)-regulatory subunit PPP1R3A, which when knocked out also led to inappropriate RyR2 activity and atrial fibrillation susceptibility in mouse [10].