G Protein-coupled Receptor Kinase 2 Negatively Regulates Chemokine Signaling at a Level Downstream from G Protein Subunits

The G protein-coupled receptor kinase 2 (GRK2) phosphorylates and desensitizes ligand-activated G protein-coupled-receptors. Here, evidence is shown for a novel role of GRK2 in regulating chemokine-mediated signals. The presence of increased levels of GRK2 in human embryonic kidney (HEK) 293 cells produced a significant reduction of the extracellular signal-regulated kinase (ERK) response to CCL2. This effect is independent of its role in receptor phosphorylation because the kinase-deficient mutant GRK2K220R was able to reduce this response, and ERK activation by CCR2BIX, a phosphorylation-defective receptor mutant, was also inhibited by GRK2. Constructs containing the Gα(q)-binding RGS-like RH domain of GRK2 or its Gβγ-binding domain could not reproduce the inhibition, thus revealing that GRK2 acts downstream of G proteins. Interestingly, chemokine-driven mitogen-activated protein kinase kinase (MEK) stimulation is not affected in cells overexpressing GRK2 or GRK2K220R or in splenocytes from heterozygous GRK2 mice, where reduced kinase levels correlate with enhanced ERK activation by chemokines. We find GRK2 and MEK in the same multimolecular complex, thus suggesting a mechanism for GRK2 regulation of ERK activity that involves a direct or coordinate interaction with MEK. These results suggest an important role for GRK2 in the control of chemokine induction of ERK activation at the level of the MEK–ERK interface

Increased Nitric Oxide Bioavailability in Adult GRK2 Hemizygous Mice Protects Against Angiotensin II-Induced Hypertension

G protein–coupled receptor kinase 2 (GRK2) is a ubiquitous serine/threonine protein kinase able to phosphorylate and desensitize the active form of several G protein–coupled receptors. Given the lack of selective inhibitors for GRK2, we investigated the effects elicited by GRK2 inhibition in vascular responses using global adult hemizygous mice (GRK2+/−). The vasodilator responses to acetylcholine or isoproterenol were increased in aortas and mesenteric resistance arteries from GRK2+/− mice compared with wild-type (WT) littermates. After angiotensin II (AngII) infusion, GRK2+/− mice were partially protected against hypertension, vascular remodeling, and mechanical alterations, even when resting basal blood pressures were not significantly different. AngII infusion also (1) increased GRK2 levels in WT but not in GRK2+/− vessels; (2) increased vasoconstrictor responses to phenylephrine in WT but not in GRK2+/− mice; and (3) decreased vasodilator responses to acetylcholine and vascular pAkt and eNOS levels more in WT than in GRK2+/− animals. Vascular NO production and the modulation of vasoconstrictor responses by endothelial-derived NO remained enhanced in GRK2+/− mice infused with AngII. Thus, GRK2+/− mice are resistant to the development of vascular remodeling and mechanical alterations, endothelial dysfunction, increased vasoconstrictor responses, and hypertension induced by AngII at least partially through the preservation of NO bioavailability. In conclusion, our results describe an important role for GRK2 in systemic hypertension and further establish that an inhibition of GRK2 could be a beneficial treatment for this condition.Ministerio de Economía y Competitividad (SAF2009-07201; SAF2011-23800, and SAF 2012-36400); Instituto de Salud Carlos III (RD06/0014/0011, RD06/0014/0037, RD12/0042/0024, RD12/0042/0012, and PS09/01208);Comunidad de Madrid (S2011/BMD-2332), UAM-Grupo Santander; Fundación Mutua Madrileñaa, Fundación Ramón Areces; and the Ramón y Cajal program (AMB, YC-2010–06473)Peer reviewe

G protein-coupled receptor kinase 2 plays a relevant role in insulin resistance and obesity

OBJECTIVE: Insulin resistance is associated with the pathogenesis of metabolic disorders as type 2 diabetes and obesity. Given the emerging role of signal transduction in these syndromes, we set out to explore the possible role that G protein-coupled receptor kinase 2 (GRK2), first identified as a G protein-coupled receptor regulator, could have as a modulator of insulin responses. RESEARCH DESIGN AND METHODS: We analyzed the influence of GRK2 levels in insulin signaling in myoblasts and adipocytes with experimentally increased or silenced levels of GRK2, as well as in GRK2 hemizygous animals expressing 50% lower levels of this kinase in three different models of insulin resistance: tumor necrosis factor-α (TNF-α) infusion, aging, and high-fat diet (HFD). Glucose transport, whole-body glucose and insulin tolerance, the activation status of insulin pathway components, and the circulating levels of important mediators were measured. The development of obesity and adipocyte size with age and HFD was analyzed. RESULTS: Altering GRK2 levels markedly modifies insulin-mediated signaling in cultured adipocytes and myocytes. GRK2 levels are increased by ∼2-fold in muscle and adipose tissue in the animal models tested, as well as in lymphocytes from metabolic syndrome patients. In contrast, hemizygous GRK2 mice show enhanced insulin sensitivity and do not develop insulin resistance by TNF-α, aging, or HFD. Furthermore, reduced GRK2 levels induce a lean phenotype and decrease age-related adiposity. CONCLUSIONS: Overall, our data identify GRK2 as an important negative regulator of insulin effects, key to the etiopathogenesis of insulin resistance and obesity, which uncovers this protein as a potential therapeutic target in the treatment of these disorders

Global attitudes in the management of acute appendicitis during COVID-19 pandemic: ACIE Appy Study

Background: Surgical strategies are being adapted to face the COVID-19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods: The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results: Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X-ray plus molecular testing (PCR) being the commonest (19\ub78 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6\ub76 and 2\ub74 per cent respectively before, but 23\ub77 and 5\ub73 per cent, during the pandemic (both P < 0\ub7001). One-third changed their approach from laparoscopic to open surgery owing to the popular (but evidence-lacking) advice from expert groups during the initial phase of the pandemic. No agreement on how to filter surgical smoke plume during laparoscopy was identified. There was an overall reduction in the number of patients admitted with appendicitis and one-third felt that patients who did present had more severe appendicitis than they usually observe. Conclusion: Conservative management of mild appendicitis has been possible during the pandemic. The fact that some surgeons switched to open appendicectomy may reflect the poor guidelines that emanated in the early phase of SARS-CoV-2