GZMK and heart failure: Alterations in β1-AR signalingsystem, sensitivity of the myocardium to β1-AR stimulation, as wellas changes in the subcellular distribution of regulatory proteins namelyG-protein-coupled receptor kinase (GRK) isoforms and β-arrestins wereobserved at different stages of heart failure due to volume overload [165, 168].Other studies have also shown increased β1-AR expression and GRKactivity as well as depressed activities of different components ofβ1-AR signaling pathways in heart failure [169, 179, 180, 181].