Transfection of miR-193a AS resulted in a small but insignificant increase in Arc mRNA

GRK5 Depends on CaM accumulation of this kinase after AngII exposure as well as significantly increased HW/BW ratios. Together, these data indicate that CaM binding to the N-terminal site of GRK5 in vivo after a hypertrophic stimulus is an absolute requirement for the pathophysiological effects of this kinase, which occur after nuclear translocation. Discussion Since its discovery, GRK5 has mainly been referenced in the context of its role in GPCR desensitization at the plasma membrane. An agonist-bound GPCR is rapidly phosphorylated by a GRK, triggering a MedChemExpress R-roscovitine conformational change and creating a docking site for b-arrestins. Internalization, followed by GPCR recycling or degradation, completes the desensitization process. Abundantly expressed in muscle, including the heart, GRK5’s predominant functions appear to encompass regulating cardiac inotropy and chronotropy downstream of the actions of catecholamines that bind and activate bARs. Up-regulated in failing myocardium, adverse effects of GRK5 initially have been attributed to bAR uncoupling and decreased inotropic reserve in HF, although GRK5 phosphorylation of some bARs can cause cardioprotection through transactivation of the epidermal growth factor receptors. Recently, we addressed the role of endogenous GRK5 in the setting of cardiac hypertrophy. Ablation of this kinase conferred cardioprotection following the stress of pressure overload, blunting myocardial hypertrophy and delaying the onset of HF. Importantly, our results demonstrated an absolute requirement for cardiomyocyte GRK5 in the adaptive and maladaptive hypertrophic response. Indeed, classically, GRK5’s primary association has been the sarcolemmal membrane, a fact thought to improve its GPCR targeting. However, increasing evidence has been amassed describing an extensive GRK5 “interactome.”New diverse substrates for GRK5 beyond GPCRs include: 7925608 IkB, asynuclein, p53, NFkB and Hip. Moreover, it has been demonstrated that GRK5 will accumulate in cellular locations distinct from the plasma membrane such as Lewy bodies and centrosomes. Most important to cardiac regulation has been the detection of 15690449 GRK5 within the nucleus of cardiomyocytes and its novel role as a HDAC kinase. Nuclear GRK5 accumulation was first recognized as a potential downstream effect of HF generation in SHHF rats. We then identified GRK5’s role as an HDAC kinase, perpetuating negative effects on the stressed heart. Nuclear localization and activity is unique to GRK5 among the GRK family. It appears to be an area ripe for potential therapeutic targeting that would prevent facilitation of maladaptive nuclear events while maintaining GPCR desensitizing capabilities. As such, we previously found that preventing GRK5 from entering the nucleus through mutation of its NLS ameliorated the accelerated hypertrophy and HF seen with increased cardiac GRK5 levels after ventricular pressure-overload. Conversely, deletion of the kinase increases nuclear HDAC5, hindering cardiomyocyte hypertrophy . Fully delineating the path of nuclear translocation would introduce the optimal place to disrupt this targeting, potentially leading to novel means of preventing HF development. Indeed, our current results, presented above, have led to the discovery of such a molecular target as we have proven the absolute mechanistic requirement for CaM in directing the nuclear translocation of GRK5 after select hypertrophic signaling. Our proposed mechanism is displayed in Fig. 7, with CaM acti