The orphan receptor GPR35 contributes to angiotensin II–induced hypertension and cardiac dysfunction in mice

BACKGROUND: The orphan receptor G protein–coupled receptor 35 (GPR35) has been associated with a range of diseases, including cancer, inflammatory bowel disease, diabetes, hypertension, and heart failure. To assess the potential for GPR35 as a therapeutic target in cardiovascular disease, this study investigated the cardiovascular phenotype of a GPR35 knockout mouse under both basal conditions and following pathophysiological stimulation. METHODS: Blood pressure was monitored in male wild-type and GPR35 knockout mice over 7–14 days using implantable telemetry. Cardiac function and dimensions were assessed using echocardiography, and cardiomyocyte morphology evaluated histologically. Two weeks of angiotensin II (Ang II) infusion was used to investigate the effects of GPR35 deficiency under pathophysiological conditions. Gpr35 messenger RNA expression in cardiovascular tissues was assessed using quantitative polymerase chain reaction. RESULTS: There were no significant differences in blood pressure, cardiac function, or cardiomyocyte morphology in GPR35 knockout mice compared with wild-type mice. Following Ang II infusion, GPR35 knockout mice were protected from significant increases in systolic, diastolic, and mean arterial blood pressure or impaired left ventricular systolic function, in contrast to wild-type mice. There were no significant differences in Gpr35 messenger RNA expression in heart, kidney, and aorta following Ang II infusion in wild-type mice. CONCLUSIONS: Although GPR35 does not appear to influence basal cardiovascular regulation, these findings demonstrate that it plays an important pathological role in the development of Ang II–induced hypertension and impaired cardiac function. This suggests that GPR35 is a potential novel drug target for therapeutic intervention in hypertension

Investigating G protein-coupled receptor 35 signalling and its role in cardiovascular disease

G protein-coupled receptors (GPCRs) are an important source of drug targets with diverse therapeutic applications. Orphan GPCRs, which have unknown endogenous ligands or physiological functions, represent a pool of potential therapeutic targets that could provide novel or improved treatments for a wide range of diseases. G protein-coupled receptor 35 (GPR35) is an orphan receptor that has been associated with several diseases and physiological processes, including gastrointenstinal disease, pain transduction, inflammation and cardiovascular disease. However, the precise function of GPR35 in these processes is yet to be elucidated. Cardiovascular disease, including hypertension and heart failure, remains a large global disease burden, suggesting that current treatments are inadequate and that novel insights might be beneficial. Therefore, the role of GPR35 in cardiovascular disease was investigated in order to assess its potential as a therapeutic target. To provide insight into the potential mechanisms of GPR35 actions in the cardiovascular system, GPR35 signalling was investigated in detail in vitro. Agonist-dependent phosphorylation was observed at five sites in the GPR35 C‑terminal tail, which differentially influenced β‑arrestin recruitment. Both agonist-dependent phosphorylation and β‑arrestin‑1/2, but not Gα12/13, were essential for agonist-induced internalisation of GPR35, an important process in the desensitisation of the G protein-mediated response. Conversely, agonist-induced reorganisation of the actin cytoskeleton was dependent on Gα12/13, but not phosphorylation or β‑arrestin. To assess the role of GPR35 in cardiovascular disease, its actions were investigated in three in vivo models. A GPR35 knockout mouse had no abnormal cardiovascular phenotype under basal conditions, with no detectable differences in blood pressure, cardiac function, vascular reactivity or end-organ morphology compared with the wild type background strain. However, GPR35 knockout mice were resistant to hypertension and cardiac dysfunction induced by 2‑week infusion of angiotensin II. Furthermore, administration of the GPR35 agonist amlexanox exacerbated both hypertension and end-organ damage in the stroke-prone spontaneously hypertensive rat. These findings demonstrate a pathological role for GPR35 in the development of hypertension and its associated end-organ damage. It is likely that this is a result of Gα13-mediated effects of GPR35 on the actin cytoskeleton in cardiovascular tissues, although this requires further investigation in primary cell models. These studies suggest that antagonism of GPR35 could be a novel therapeutic strategy to treat hypertension and/or heart failure. The findings must now be validated by antagonising GPR35 in in vivo disease models, in order to evaluate the therapeutic value of this strategy

Representation of finite groups and the first Betti number of branched coverings of a universal Borromean orbifold

The paper investigates the first homology of the regular branched coverings of universal Borromean orbifold B_4_,_4_,_4 backslash H"3, whose arithmetic structures are intensively studied in [HLM1]. The action of the group G of the covering transformations on the first homology is studied to obtain a criterion for an irreducible representation of G to be an irreducible component of the first homology with particular enthusiasm on the principal congruent subgroups. The investigation is motivated by a problem of the three dimensional topology due to Thurston and provides a criterion for a class of 3-manifolds to have a finite sheeted covering of positive first Betti number in terms of the group theory. (orig.)SIGLEAvailable from TIB Hannover: RR 1596(386) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Agonist-induced phosphorylation of orthologues of the orphan receptor GPR35 functions as an activation sensor.

G protein-coupled receptor 35 (GPR35) is poorly characterized but nevertheless has been revealed to have diverse roles in areas including lower gut inflammation and pain. The development of novel reagents and tools will greatly enhance analysis of GPR35 functions in health and disease. Here, we used mass spectrometry, mutagenesis, and [32P] orthophosphate labeling to identify that all five hydroxy-amino acids in the C-terminal tail of human GPR35a became phosphorylated in response to agonist occupancy of the receptor and that, apart from Ser294, each of these contributed to interactions with arretin-3, which inhibits further G protein-coupled receptor signaling. We found that Ser303 was key to such interactions; the serine corresponding to human GPR35a residue 303 also played a dominant role in arrestin-3 interactions for both mouse and rat GPR35. We also demonstrated that fully phospho-site-deficient mutants of human GPR35a and mouse GPR35 failed to interact effectively with arrestin-3, and the human phospho-deficient variant was not internalized from the surface of cells in response to agonist treatment. Even in cells stably expressing species orthologues of GPR35, a substantial proportion of the expressed protein(s) was determined to be immature. Finally, phospho-site-specific antisera targeting the region encompassing Ser303 in human (Ser301 in mouse) GPR35a identified only the mature forms of GPR35 and provided effective sensors of the activation status of the receptors both in immunoblotting and immunocytochemical studies. Such antisera may be useful tools to evaluate target engagement in drug discovery and target validation programs