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Inflammatory bowel disease (IBD) is an important cause of morbidity and mortality for millions of patients worldwide. Current treatment options include corticosteroids, 5-aminosalicylates, immunosuppressants, and TNFa antagonists. However, these are frequently ineffective in achieving sustained response and remission over time. At present, gastroenterologists lack safe and effective treatments if patients fail anti-TNF therapy. Vedolizumab is a promising new agent for IBD patients refractory to anti-TNF therapy. Vedolizumab is an integrin antagonist which is thought to act by reducing inflammation by selectively inhibiting leukocyte migration in the gut. Emerging evidence from clinical trials suggests a potential role for vedolizumab in both ulcerative colitis (UC) and Crohn's disease (CD), particularly in patients who have previously failed biological therapy. The safety profile of vedolizumab appears reasonable, possibly because it has a "gut-selective" mode of action, with no reported cases of progressive multifocal leukoencephalopathy, a condition which has been linked to another integrin antagonist, natalizumab. This review discusses the available evidence for integrin antagonists and their potential role in the management of IBD. [ABSTRACT FROM AUTHOR]

Spinophilin (SPL) and neurabin (NRB) are structurally similar scaffolding proteins with several protein binding modules, including actin and PP1 binding motifs and PDZ and coiled-coil domains. SPL also binds regulators of G protein signaling (RGS) proteins and the third intracellular loop (3iL) of G protein-coupled receptors (GPCRs) to reduce the intensity of Ca2+ signaling by GPCRs. The role of NRB in Ca2+ signaling is not known. In the present work, we used biochemical and functional assays in model systems and in SPL−/− and NRB−/− mice to show that SPL and NRB reciprocally regulate Ca2+ signaling by GPCRs. Thus, SPL and NRB bind all members of the R4 subfamily of RGS proteins tested (RGS1, RGS2, RGS4, RGS16) and GAIP. By contract, SPL, but not NRB, binds the 3iL of the GPCRs α1B-adrenergic (α1BAR), dopamine, CCKA, CCKB and the muscarinic M3 receptors. Coexpression of SPL or NRB with the α1BAR in Xenopus oocytes revealed that SPL reduces, whereas NRB increases, the intensity of Ca2+ signaling by α1BAR. Accordingly, deletion of SPL in mice enhanced binding of RGS2 to NRB and Ca2+ signaling by αAR, whereas deletion of NRB enhanced binding of RGS2 to SPL and reduced Ca2+ signaling by αAR. This was due to reciprocal modulation by SPL and NRB of the potency of RGS2 to inhibit Ca2+ signaling by αAR. These findings suggest a novel mechanism of regulation of GPCR-mediated Ca2+ signaling in which SPL/NRB forms a functional pair of opposing regulators that modulates Ca2+ signaling intensity by GPCRs by determining the extent of inhibition by the R4 family of RGS proteins. [ABSTRACT FROM AUTHOR]

The noradrenergic system in the prefrontal cortex (PFC) is involved in many physiological and psychological processes, including working memory and mood control. To understand the functions of the noradrenergic system, we examined the regulation of NMDA receptors (NMDARs), key players in cognition and emotion, by α1- and α2-adrenergic receptors (α1-ARs, α2-ARs) in PFC pyramidal neurons. Applying norepinephrine or a norepinephrine transporter inhibitor reduced the amplitude but not paired-pulse ratio of NMDAR-mediated excitatory postsynaptic currents (EPSC) in PFC slices. Specific α1-AR or α2-AR agonists also decreased NMDAR-EPSC amplitude and whole-cell NMDAR current amplitude in dissociated PFC neurons. The al-AR effect depended on the phospholipase C-inositol 1,4,5-trisphosphate-Ca2+ pathway, whereas the α2-AR effect depended on protein kinase A and the microtubule-based transport of NMDARs that is regulated by ERK signaling. Furthermore, two members of the RGS family, RGS2 and RGS4, were found to down-regulate the effect of α1-AR on NMDAR currents, whereas only RGS4 was involved in inhibiting α2-AR regulation of NMDAR currents. The regulating effects of RGS2/4 on α1-AR signaling were lost in mutant mice lacking spinophilin, which binds several RGS members and G protein-coupled receptors, whereas the effect of RGS4 on α2-AR signaling was not altered in spinophilin-knockout mice. Our work suggests that activation of α1-ARs or α2-ARs suppresses NMDAR currents in PFC neurons by distinct mechanisms. The effect of al-ARs is modified by RGS2/4 that are recruited to the receptor complex by spinophilin, whereas the effect of α2-ARs is modified by RGS4 independent of spinophilin. [ABSTRACT FROM AUTHOR]

Signalling by G proteins is controlled by the regulator of G-protein signalling (RGS) proteins that accelerate the GTPase activity of Gasubunits and act in a G-protein-coupled receptor (GPCR)-specific manner. The conserved RGS domain accelerates the G subunit GTPase activity, whereas the variable amino-terminal domain participates in GPCR recognition. How receptor recognition is achieved is not known. Here, we show that the scaffold protein spinophilin (SPL), which binds the third intracellualar loop (3iL) of several GPCRs, binds the N-terminal domain of RGS2. SPL also binds RGS1, RGS4, RGS16 and GAIP. When expressed in Xenopus laevis oocytes, SPL markedly increased inhibition ofa-adrenergic receptor (aAR) Ca2+ signalling by RGS2. Notably, the constitutively active mutantaARA293E (the mutation being in the 3iL) did not bind SPL and was relatively resistant to inhibition by RGS2. Use ofßAR-aAR chimaeras identified the288REKKAA293 sequence as essential for the binding of SPL and inhibition of Ca2+ signalling by RGS2. Furthermore,aAR-evoked Ca2+ signalling is less sensitive to inhibition by SPL in rgs2-/- cells and less sensitive to inhibition by RGS2 in spl-/- cells. These findings provide a general mechanism by which RGS proteins recognize GPCRs to confer signalling specificity. [ABSTRACT FROM AUTHOR]

Spinophilin is a protein phosphatase-1- and actin-binding protein that modulates excitatory synaptic transmission and dendritic spine morphology. We have recently shown that the interaction of spinophilin with the actin cytoskeleton depends upon phosphorylation by protein kinase A. We have now found that spinophilin is phosphorylated by Ca2+/calmodulin-dependent protein kinase II (CaMKII) in neurons. Ca2+/calmodulin-dependent protein kinase II, located within the post-synaptic density of dendritic spines, is known to play a role in synaptic plasticity and is ideally positioned to regulate spinophilin. Using tryptic phosphopeptide mapping, site-directed mutagenesis and microsequencing analysis, we identified two sites of CaMKII phosphorylation (Ser-100 and Ser-116) within the actin-binding domain of spinophilin. Phosphorylation by CaMKII reduced the affinity of spinophilin for F-actin. In neurons, phosphorylation at Ser-100 by CaMKII was Ca2+ dependent and was associated with an enrichment of spinophilin in the synaptic plasma membrane fraction. These results indicate that spinophilin is phosphorylated by multiple kinases in vivo and that differential phosphorylation may target spinophilin to specific locations within dendritic spines. [ABSTRACT FROM AUTHOR]

Abstract: The role of the dopamine- and cyclic AMP-regulated phosphoprotein of Mr 32,000 (DARPP-32) in dopaminergic regulation of gene transcription in striatum and globus pallidus was examined. Mice with targeted disruption of the gene encoding DARPP-32, its homologue, inhibitor-1, or both, were used. Pharmacological characterization showed that mutant mice had normal basal levels of dopamine D1 and D2 receptors and adenosine A2A receptors. Basal expression levels of the striatonigral-specific neuropeptides substance P and prodynorphin and the immediate early genes c-fos and NGFI-A were also unaltered in mutant mice. A full D1 receptor agonist, SKF 82958, up-regulated the expression of these neuropeptides and immediate early genes significantly more in wild-type mice than in mice lacking DARPP-32. Moreover, the additive stimulation of SKF 82958 and quinelorane, a D2 receptor agonist, on c-fos mRNA in globus pallidus was significantly decreased in DARPP-32 and DARPP-32/I-1 knockout mice. No changes in dopamine receptor-induced gene expression were found in I-1 knockout mice. These results demonstrate an important involvement of DARPP-32 in dopamine receptor-mediated regulation of gene expression both in striatal neurons, which are enriched in DARPP-32, and in pallidal neurons, which do not contain DARPP-32. [ABSTRACT FROM AUTHOR]

Modulation of AMPA-type glutamate channels is important for synaptic plasticity. Here we provide physiological evidence that the activity of AMPA channels is regulated by protein phosphatase 1 (PP-1) in neostriatal neurons and identify two distinct molecular mechanisms of this regulation. One mechanism involves control of PP-1 catalytic activity by DARPP-32, a dopamine- and cAMP-regulated phosphoprotein highly enriched in neostriatum. The other involves binding of PP-1 to spinophilin, a protein that colocalizes PP-1 with AMPA receptors in postsynaptic densities. The results suggest that regulation of anchored PP-1 is important for AMPA-receptor-mediated synaptic transmission and plasticity. [ABSTRACT FROM AUTHOR]

A 30-year-old man presented with a 6- month history of nausea, vomiting and diarrhoea. This was associated with 25 kg weight loss and a right-sided abdominal colic. He had been provisionally diagnosed with Crohn's disease 6 months back and treated with budesonide and mesalazine. Investigations including C reactive protein, white cell count, coeliac antibodies, fasting gut hormones and faecal elastase were all normal. Colonoscopy and ileoscopy were normal both macroscopically and microscopically. Small bowel series and labelled white cell scan were both unremarkable. A CT scan suggested the presence of mild right-sided abdominal lymphadenopathy. Laparoscopy of entire small bowel and colon was normal. But had something been missed? An adrenocorticotrophic hormone stimulation test demonstrated inadequate cortisol response and a diagnosis of adrenal insufficiency was confirmed. Addison's disease can present with a variety of gastrointestinal symptoms and should be considered in the diagnostic work-up of these patients. [ABSTRACT FROM AUTHOR]

Examines the biochemical properties of Phosphatase 1 Nuclear Targeting Subunit (PNUTS), a protein that targets protein phosphatase (PP) 1 to the nucleus. Truncation and site-directed mutants of PNUTS; Results of in vitro RNA binding experiments; Regulation of PP1 activity by PNUTS.

Arrestin regulates almost all G protein-coupled receptor (GPCR) — mediated signaling and trafficking. We report that the multidomain protein, spinophilin, antagonizes these multiple arrestin functions. Through blocking G protein receptor kinase 2 (GRK2) association with receptor-Gβy complexes, spinophilin reduces arrestin-stabilized receptor phosphorylation, receptor endocytosis, and the acceleration of mitogenactivated protein kinase (MARK) activity following endocytosis. Spinophilin knockout mice were more sensitive than wild-type mice to sedation elicited by stimulation of α² adrenergic receptors, whereas arrestin 3 knockout mice were more resistant, indicating that the signal-promoting rather than the signal-terminating, roles of arrestin are more important for certain response pathways. The reciprocal interactions of GPCRs with spinophilin and arrestin represent a regulatory mechanism for fine-tuning complex receptor-orchestrated cell signaling and responses. [ABSTRACT FROM AUTHOR]

Inflammatory bowel diseases (IBD) are chronic relapsing and remitting disorders that have varying degrees of severity. However multiple studies have confirmed that a large proportion of patients on maintenance treatment lose response to anti-TNF therapy. This has led to increasing interest in the concept of 'switching therapy out-of-class' i.e. a nonanti- TNF antibody when patients either fail to respond (primary non-response, develop secondary non-response) or do not tolerate anti-TNF therapies. The most widely known and studied alternative class of antibodies therapies at present are the selective adhesion molecule inhibitors. Several antibodies exist which constitute selection adhesion molecule inhibitors, including Natalizumab, MLN-0002 (Vedolizumab) and ISIS 2302 (Alicaforsen) will be discussed in this review.

Infliximab has demonstrated its efficacy in moderate to severe ulcerative colitis. The Active Ulcerative Colitis Trial (ACT) -1 and 2 have demonstrated the beneficial impact of infliximab on the short-term colectomy rate. However, data evaluating this outcome beyond one year remains scarce. To provide evidence on the potential impact of infliximab on the long-term colectomy rate in patients suffering from ulcerative colitis, data was reviewed from randomized and controlled studies, referral centre studies and population-based studies, in adult and pediatric populations. In the pre-biologic era, 9-33%, 50% and 29% of adult patients with ulcerative colitis underwent colectomy in clinical trials, referral center studies and population-based cohorts, respectively. In the pediatric population, 9-61% and 8-20% underwent colectomy in referral centers and population-based cohorts, respectively. Between 10 and 36% of adult patients treated with infliximab for ulcerative colitis underwent colectomy in clinical trials, referral center studies and population-based cohorts. In the pediatric population treated with infliximab, long-term data is lacking, with colectomy rates ranging from 16 to 28%. Whether infliximab proves to be a disease modifying treatment in ulcerative colitis in the long term remains to be elucidated and will require further long-term prospective studies.

Agonist activation regulates reciprocal interactions of spinophilin and arrestin with the alpha2A- and alpha2B -adrenergic receptor (AR) subtypes via their 3i loop. Because arrestin association with G protein-coupled receptor is preceded by redistribution of arrestin to the cell surface, the present studies explored whether agonist activation of the alpha2A- and alpha2B -AR subtypes also led to spinophilin enrichment at the cell surface. Live cell imaging studies using a green fluorescent protein-tagged spinophilin examined spinophilin localization and its regulation by alpha2 -AR agonist. Agonist activation of alpha2A-AR preferentially, compared with the alpha2B-AR, led to spinophilin enrichment at the cell surface in human embryonic kidney 293 cells and in mouse embryo fibroblasts derived from spinophilin null mice. Activation of the delta LEESSSS alpha2A-AR, which has enriched association with spinophilin compared with the wild-type (WT) alpha2A-AR, does not show an enhanced redistribution of spinophilin to the surface compared with WT alpha2A-AR, demonstrating that the ability or affinity of the receptor in binding spinophilin may be independent of the ability of the receptor to effect spinophilin redistribution to the surface. Agonist-evoked enrichment of spinophilin at the cell surface seems to involve downstream signaling events, manifested both by the pertussis toxin sensitivity of the process and by the marked attenuation of spinophilin redistribution in cells expressing the beta-adrenergic receptor kinase-C tail, which sequesters beta gamma subunits of G proteins. Together, the data suggest that agonist-evoked spinophilin enrichment at the cell surface is caused by receptor-evoked signaling pathways and is independent of the affinity of the receptor for the spinophilin molecule.