Functional evidence for biased inhibition of G protein signaling by YM-254890 in human coronary artery endothelial cells.

Small molecular chemicals targeting individual subtype of G proteins including Gs, Gi/o and Gq has been lacking, except for pertussis toxin being an established selective peptide inhibitor of the Gi/o protein. Recently, a cyclic depsipeptide compound YM-254890 isolated from culture broth of Chromobacterium sp. was reported as a selective inhibitor for the Gq protein by blocking GDP exchange of GTP on the α subunit of Gq complex. However, functional selectivity of YM-254890 towards various G proteins was not fully characterized, primarily due to its restricted availability before 2017. Here, using human coronary artery endothelial cells as a model, we performed a systemic pharmacological evaluation on the functional selectivity of YM-254890 on multiple G protein-mediated receptor signaling. First, we confirmed that YM-254890, at 30 nM, abolished UTP-activated P2Y2 receptor-mediated Ca2+ signaling and ERK1/2 phosphorylation, indicating its potent inhibition on the Gq protein. However, we unexpectedly found that YM-254890 also significantly suppressed cAMP elevation and ERK1/2 phosphorylation induced by multiple Gs-coupled receptors including ß2-adrenegic, adenosine A2 and PGI2 receptors. Surprisingly, although YM-254890 had no impact on CXCR4/Gi/o protein-mediated suppression of cAMP production, it abolished ERK1/2 activation. Further, no cellular toxicity was observed for YM-254890, and it neither affected A23187- or thapsigargin-induced Ca2+ signaling, nor forskolin-induced cAMP elevation and growth factor-induced MAPK signaling. We conclude that YM-254890 is not a selective inhibitor for Gq protein; instead, it acts as a broad-spectrum inhibitor for Gq and Gs proteins and exhibits a biased inhibition on Gi/o signaling, without affecting non-GPCR-mediated cellular signaling.

Delineation of molecular determinants for FR900359 inhibition of Gq/11 unlocks inhibition of Gαs.

Heterotrimeric G proteins are essential mediators of intracellular signaling of G protein-coupled receptors. The Gq/11 subfamily consists of Gq, G11, G14, and G16 proteins, of which all but G16 are inhibited by the structurally related natural products YM-254890 and FR900359. These inhibitors act by preventing the GDP/GTP exchange, which is necessary for activation of all G proteins. A homologous putative binding site for YM-254890/FR900359 can also be found in members of the other three G protein families, Gs, Gi/o, and G12/13, but none of the published analogs of YM-254890/FR900359 have shown any inhibitory activity for any of these. To explain why the YM-254890/FR900359 scaffold only inhibits Gq/11/14, the present study delineated the molecular selectivity determinants by exchanging amino acid residues in the YM-254890/FR900359-binding site in Gq and Gs We found that the activity of a Gs mutant with a Gq-like binding site for YM-254890/FR900359 can be inhibited by FR900359, and a minimum of three mutations are necessary to introduce inhibition in Gs In all, this suggests that although the YM-254890/FR900359 scaffold has proven unsuccessful to derive Gs, Gi/o, and G12/13 inhibitors, the mechanism of inhibition between families of G proteins is conserved, opening up the possibility of targeting by other, novel inhibitor scaffolds. In lack of a selective Gαs inhibitor, FR900359-sensitive Gαs mutants may prove useful in studies where delicate control over Gαs signaling would be of the essence.

Direct targeting of Gαq and Gα11 oncoproteins in cancer cells.

Somatic gain-of-function mutations of GNAQ and GNA11, which encode α subunits of heterotrimeric Gαq/11 proteins, occur in about 85% of cases of uveal melanoma (UM), the most common cancer of the adult eye. Molecular therapies to directly target these oncoproteins are lacking, and current treatment options rely on radiation, surgery, or inhibition of effector molecules downstream of these G proteins. A hallmark feature of oncogenic Gαq/11 proteins is their reduced intrinsic rate of hydrolysis of guanosine triphosphate (GTP), which results in their accumulation in the GTP-bound, active state. Here, we report that the cyclic depsipeptide FR900359 (FR) directly interacted with GTPase-deficient Gαq/11 proteins and preferentially inhibited mitogenic ERK signaling rather than canonical phospholipase Cß (PLCß) signaling driven by these oncogenes. Thereby, FR suppressed the proliferation of melanoma cells in culture and inhibited the growth of Gαq-driven UM mouse xenografts in vivo. In contrast, FR did not affect tumor growth when xenografts carried mutated B-RafV600E as the oncogenic driver. Because FR enabled suppression of malignant traits in cancer cells that are driven by activating mutations at codon 209 in Gαq/11 proteins, we envision that similar approaches could be taken to blunt the signaling of non-Gαq/11 G proteins.

Rational design of a heterotrimeric G protein α subunit with artificial inhibitor sensitivity.

Transmembrane signals initiated by a range of extracellular stimuli converge on members of the Gq family of heterotrimeric G proteins, which relay these signals in target cells. Gq family G proteins comprise Gq, G11, G14, and G16, which upon activation mediate their cellular effects via inositol lipid-dependent and -independent signaling to control fundamental processes in mammalian physiology. To date, highly specific inhibition of Gq/11/14 signaling can be achieved only with FR900359 (FR) and YM-254890 (YM), two naturally occurring cyclic depsipeptides. To further development of FR or YM mimics for other Gα subunits, we here set out to rationally design Gα16 proteins with artificial FR/YM sensitivity by introducing an engineered depsipeptide-binding site. Thereby we permit control of G16 function through ligands that are inactive on the WT protein. Using CRISPR/Cas9-generated Gαq/Gα11-null cells and loss- and gain-of-function mutagenesis along with label-free whole-cell biosensing, we determined the molecular coordinates for FR/YM inhibition of Gq and transplanted these to FR/YM-insensitive G16. Intriguingly, despite having close structural similarity, FR and YM yielded biologically distinct activities: it was more difficult to perturb Gq inhibition by FR and easier to install FR inhibition onto G16 than perturb or install inhibition with YM. A unique hydrophobic network utilized by FR accounted for these unexpected discrepancies. Our results suggest that non-Gq/11/14 proteins should be amenable to inhibition by FR scaffold-based inhibitors, provided that these inhibitors mimic the interaction of FR with Gα proteins harboring engineered FR-binding sites.

Effects of Oncogenic Gαq and Gα11 Inhibition by FR900359 in Uveal Melanoma.

Uveal melanoma is the most common intraocular tumor in adults and often metastasizes to the liver, leaving patients with few options. Recurrent activating mutations in the G proteins, Gαq and Gα11, are observed in approximately 93% of all uveal melanomas. Although therapeutic intervention of downstream Gαq/11 targets has been unsuccessful in treating uveal melanoma, we have found that the Gαq/11 inhibitor, FR900359 (FR), effectively inhibits oncogenic Gαq/11 signaling in uveal melanoma cells expressing either mutant Gαq or Gα11. Inhibition of oncogenic Gαq/11 by FR results in cell-cycle arrest and induction of apoptosis. Furthermore, colony formation is prevented by FR treatment of uveal melanoma cells in 3D-cell culture, providing promise for future in vivo studies. This suggests direct inhibition of activating Gαq/11 mutants may be a potential means of treating uveal melanoma. IMPLICATIONS: Oncogenic Gαq/11 inhibition by FR900359 may be a potential treatment option for those with uveal melanoma.

Role of age, Rho-kinase 2 expression, and G protein-mediated signaling in the myogenic response in mouse small mesenteric arteries.

The myogenic response (MR) and myogenic tone (MT) in resistance vessels is crucial for maintaining peripheral vascular resistance and blood flow autoregulation. Development of MT involves G protein-coupled receptors, and may be affected by aging. AIMS: (1) to estimate the mesenteric blood flow in myogenically active small mesenteric arteries; (2) to investigate the signaling from Gαq/11 and/or Gα12 activation to MT development; (3) to investigate the role of Rho-kinase 2 and aging on MT in mesenteric resistance arteries. METHODS: we used pressure myography, quantitative real-time PCR, and immunolocalization to study small (<200 µm) mesenteric arteries (SMA) from young, mature adult, and middle aged mice. RESULTS: Poiseuille flow calculations indicated autoregulation of blood flow at 60-120 mm Hg arterial pressure. Gαq/11 and Gα12 were abundantly expressed at the mRNA and protein levels in SMA. The Gαq/11 inhibitor YM-254890 suppressed MT development, and the Phosholipase C inhibitors U73122 and ET-18-OCH3 robustly inhibited it. We found an age-dependent increase in ROCK2 mRNA expression, and in basal MT. The specific ROCK2 inhibitor KD025 robustly inhibited MT in SMAs in all mice with an age-dependent variation in KD025 sensitivity. The inhibitory effect of KD025 was not prevented by the L-type Ca2+ channel activator BayK 8644. KD025 reversibly inhibited MT and endothelin-1 vasoconstriction in small pial arteries from Göttingen minipigs. CONCLUSIONS: MT development in SMAs occurs through a Gαq/11 /PLC/Ca2+ -dependent pathway, and is maintained via ROCK2-mediated Ca2+ sensitization. Increased MT at mature adulthood can be explained by increased ROCK2 expression/activity.

Targeting nucleotide exchange to inhibit constitutively active G protein α subunits in cancer cells.

Constitutively active G protein α subunits cause cancer, cholera, Sturge-Weber syndrome, and other disorders. Therapeutic intervention by targeted inhibition of constitutively active Gα subunits in these disorders has yet to be achieved. We found that constitutively active Gαq in uveal melanoma (UM) cells was inhibited by the cyclic depsipeptide FR900359 (FR). FR allosterically inhibited guanosine diphosphate-for-guanosine triphosphate (GDP/GTP) exchange to trap constitutively active Gαq in inactive, GDP-bound Gαßγ heterotrimers. Allosteric inhibition of other Gα subunits was achieved by the introduction of an FR-binding site. In UM cells driven by constitutively active Gαq, FR inhibited second messenger signaling, arrested cell proliferation, reinstated melanocytic differentiation, and stimulated apoptosis. In contrast, FR had no effect on BRAF-driven UM cells. FR promoted UM cell differentiation by reactivating polycomb repressive complex 2 (PRC2)-mediated gene silencing, a heretofore unrecognized effector system of constitutively active Gαq in UM. Constitutively active Gαq and PRC2 therefore provide therapeutic targets for UM. The development of FR analogs specific for other Gα subunit subtypes may provide novel therapeutic approaches for diseases driven by constitutively active Gα subunits or multiple G protein-coupled receptors (GPCRs) where targeting a single receptor is ineffective.

"Disruptor" residues in the regulator of G protein signaling (RGS) R12 subfamily attenuate the inactivation of Gα subunits.

Understanding the molecular basis of interaction specificity between RGS (regulator of G protein signaling) proteins and heterotrimeric (αßγ) G proteins would enable the manipulation of RGS-G protein interactions, explore their functions, and effectively target them therapeutically. RGS proteins are classified into four subfamilies (R4, R7, RZ, and R12) and function as negative regulators of G protein signaling by inactivating Gα subunits. We found that the R12 subfamily members RGS10 and RGS14 had lower activity than most R4 subfamily members toward the Gi subfamily member Gαo Using structure-based energy calculations with multiple Gα-RGS complexes, we identified R12-specific residues in positions that are predicted to determine the divergent activity of this subfamily. This analysis predicted that these residues, which we call "disruptor residues," interact with the Gα helical domain. We engineered the R12 disruptor residues into the RGS domains of the high-activity R4 subfamily and found that these altered proteins exhibited reduced activity toward Gαo Reciprocally, replacing the putative disruptor residues in RGS18 (a member of the R4 subfamily that exhibited low activity toward Gαo) with the corresponding residues from a high-activity R4 subfamily RGS protein increased its activity toward Gαo Furthermore, the high activity of the R4 subfamily toward Gαo was independent of the residues in the homologous positions to the R12 subfamily and RGS18 disruptor residues. Thus, our results suggest that the identified RGS disruptor residues function as negative design elements that attenuate RGS activity for specific Gα proteins.

GNA11 differentially mediates fibroblast growth factor 2- and vascular endothelial growth factor A-induced cellular responses in human fetoplacental endothelial cells.

KEY POINTS: Fetoplacental vascular growth is critical to fetal growth. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are two major regulators of fetoplacental vascular growth. G protein α subunit 11 (GNA11) transmits signals from many external stimuli to the cellular interior and may mediate endothelial function. It is not known whether GNA11 mediates FGF2- and VEGFA-induced endothelial cell responses under physiological chronic low O2 . In the present study, we show that knockdown of GNA11 significantly decreases FGF2- and VEGFA-induced fetoplacental endothelial cell migration but not proliferation and permeability. Such decreases in endothelial migration are associated with increased phosphorylation of phospholipase C-ß3. The results of the present study suggest differential roles of GNA11 with respect to mediating FGF2- and VEGFA-induced fetoplacental endothelial function. ABSTRACT: During pregnancy, fetoplacental angiogenesis is dramatically increased in association with rapidly elevated blood flow. Any disruption of fetoplacental angiogenesis may lead to pregnancy complications such as intrauterine growth restriction. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are crucial regulators of fetoplacental angiogenesis. G protein α subunits q (GNAq) and 11 (GNA11) are two members of the Gαq/11 subfamily involved in mediating vascular growth and basal blood pressure. However, little is known about the roles of GNA11 alone with respect to mediating the FGF2- and VEGFA-induced fetoplacental endothelial function. Using a cell model of human umbilical cord vein endothelial cells cultured under physiological chronic low O2 (3% O2 ), we showed that GNA11 small interfering RNA (siRNA) dramatically inhibited (P < 0.05) FGF2- and VEGFA-stimulated fetoplacental endothelial migration (by ∼36% and ∼50%, respectively) but not proliferation and permeability. GNA11 siRNA also elevated (P < 0.05) FGF2- and VEGFA-induced phosphorylation of phospholipase C-ß3 (PLCß3) at S537 in a time-dependent fashion but not mitogen-activated protein kinase 3/1 (ERK1/2) and v-akt murine thymoma viral oncogene homologue 1 (AKT1). These data suggest that GNA11 mediates FGF2- and VEGFA-stimulated fetoplacental endothelial cell migration partially via altering the activation of PLCß3.

Impairment of the Gnα11-controlled expression of claudin-1 and MMP-9 and collective migration of human breast cancer MCF-7 cells by DHEAS.

Although dehydroepiandrosterone sulfate (DHEAS) constitutes the most abundant steroid in humans, in-depth investigations of its effects are rather scarce. We address here DHEAS effects on the estrogen receptor-positive metastatic human breast cancer cell line MCF-7. We focus on DHEAS-mediated signaling that might influence expression of claudin-1 and matrix metalloproteinase-9 (MMP-9), both known to be critical factors for migration and invasiveness of various cancers, including breast cancer cells. Physiological concentrations of DHEAS trigger persistent phosphorylation of Erk1/2 in MCF-7 cells. Exposure of these cells for 24 h to 1 µM DHEAS also leads to a significant reduction of claudin-1 expression that cannot be prevented by high concentrations of the steroid sulfatase inhibitor STX64, indicating that desulfation and further conversion of DHEAS to some other steroid hormone is not required for this action. In addition, exposure of MCF-7 cells to the same concentration of DHEAS completely abolishes MMP-9 expression and considerably impairs cell migratory behavior. Abrogation of Gnα11 expression by siRNA prevents the stimulatory effect of DHEAS on Erk1/2 phosphorylation, consistent with a G-protein-coupled receptor being involved in the DHEAS-induced signaling. Nevertheless, Gnα11 also has direct effects that do not depend on DHEAS; thus, when Gnα11 expression is suppressed, expression of claudin-1 and MMP-9 as well as cell migration are significantly reduced. This is the first report demonstrating direct involvement of DHEAS and Gnα11 in the regulation of claudin-1 and MMP-9 expression and migration of MCF-7 cells.

Lysophosphatidic acid enhances human umbilical cord mesenchymal stem cell viability without differentiation via LPA receptor mediating manner.

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are potential stromal cells which are regarded as the most feasible stem cell group in cell therapy. The maintenance of cell survival without differentiation is important in cell transplantation and stem cell therapy. However, negative factors exist in cell transplantation. Lysophosphatidic acid (LPA) is a non-antigenic small molecule phospholipid which induced several fundamental cellular responses, such as cell proliferation, apoptosis and migration. In this study we aimed to explore the effects of LPA on the survival and differentiation of MSCs and its availability in cell therapy. We found that LPA stimulated hUC-MSC proliferation and protected hUC-MSCs from lipopolysaccharide (LPS) induced apoptosis. We also observed that CD29, CD44, CD73, CD90 and CD105 were expressed, whereas CD34 and CD45 were not expressed in hUC-MSCs, and these makers have no change in LPA containing medium, which indicated that LPA accelerated the survival of hUC-MSCs in an undifferentiating status. We also demonstrated that higher expressed LPAR1 involved in LPA stimulated cell survival action. LPA stimulated cell proliferation was associated with LPAR1 mediated Gi/o-proteins/ERK1/2 pathway. On the other hand, LPA protected hUC-MSCs from LPS-induced apoptosis through suppressing caspase-3 activation by LPAR1 coupled with a G protein, but not Gi/o or Gq/11 in hUC-MSC. Collectively, this study demonstrated that LPA increased the proliferation and survival of hUC-MSCs without differentiation through LPAR1 mediated manner. Our findings provide that LPA as a anti-apoptotic agent having potential application prospect in cell transplantation and stem cell therapy.

Dehydroepiandrosterone sulfate augments blood-brain barrier and tight junction protein expression in brain endothelial cells.

Tight junctions (TJ) between brain endothelial cells are essential for formation and maintenance of the blood-brain barrier (BBB). Although loss of BBB integrity is associated with several neuropathological disorders, treatments that augment or stabilise the BBB are scarce. Here we show that physiological concentrations of dehydroepiandrosterone sulfate (DHEAS) stimulate the expression of the TJ proteins zonula occludens-1 (ZO-1) and claudin-3 in the brain-derived endothelial cell line bEnd.3 and promote TJ formation between neighbouring cells, demonstrated by augmented transendothelial resistance across cell monolayers. Silencing androgen receptor expression by siRNA does not prevent DHEAS-induced stimulation of ZO-1 expression, indicating that conversion of DHEAS into testosterone is not required for its actions. Suppression of Gnα11 expression by siRNA prevents DHEAS actions, pointing towards a G-protein-coupled receptor as being a mediator of the DHEAS effects. These results are consistent with the idea that DHEAS, acting as a hormone in its own right, supports the integrity of the BBB. The current findings might help in developing new strategies for the prevention or treatment of neurological disorders associated with BBB defects.

Identification of residues crucial for the interaction between human neuroglobin and the α-subunit of heterotrimeric Gi protein.

Mammalian neuroglobin (Ngb) protects neuronal cells under conditions of oxidative stress. We previously showed that human Ngb acts as a guanine nucleotide dissociation inhibitor (GDI) for the α-subunits of heterotrimeric Gi/o proteins and inhibits the decrease in cAMP concentration, leading to protection against cell death. In the present study, we used an eukaryotic expression vector driving high-level expression of human wild-type Ngb or Ngb mutants that either exhibit or lack GDI activities in human cells. We demonstrate that the GDI activity of human Ngb is tightly correlated with its neuroprotective activity. We further demonstrate that Glu53, Glu60, and Glu118 of human Ngb are crucial for both the neuroprotective activity and interaction with Gαi1. Moreover, we show that Lys46, Lys70, Arg208, Lys209, and Lys210 residues of Gαi1 are important for binding to human Ngb. We propose a molecular docking model of the complex between human Ngb and Gαi1.

'Smelling' the cerebrospinal fluid: olfactory signaling molecules are expressed in and mediate chemosensory signaling from the choroid plexus.

The olfactory-type signaling machinery has been known to be involved not only in odorant detection but also in other tissues with unsuspected sensory roles. As a barrier, the choroid plexus (CP) is an active participant in the monitoring of the cerebrospinal fluid (CSF), promptly responding to alterations in its composition. We hypothesized that olfactory signaling could be active in CP, contributing to the surveillance of the CSF composition. We determined the mRNA and protein expression of the major components of the olfactory transduction pathway in the rat CP, including odorant receptors, the olfactory G-protein (Gαolf), adenylate cyclase 3 and cyclic nucleotide-gated channel 2. The functionality of the transduction pathway and the intracellular mechanisms involved were analyzed by DC field potential recording electrophysiological analysis, in an ex vivo CP-brain setup, using polyamines as stimuli and blockers of the downstream signaling pathways. Concentration-dependent responses were obtained for the polyamines studied (cadaverine, putrescine, spermine and spermidine), all known to be present in the CSF. Transfection of a CP epithelial cell line with siRNA against Gαolf effectively knocked down protein expression and reduced the CP cells' response to spermine. Thus, the key components of the olfactory chemosensory apparatus are present and are functional in murine CP, and polyamines seem to trigger both the cAMP and the phospholipase C-inositol 1,4,5-trisphosphate pathways. Olfactory-like chemosensory signaling may be an essential component of the CP chemical surveillance apparatus to detect alterations in the CSF composition, and to elicit responses to modulate and maintain brain homeostasis.

Using siRNA to define functional interactions between melanopsin and multiple G Protein partners.

Melanopsin expressing photosensitive retinal ganglion cells (pRGCs) represent a third class of ocular photoreceptors and mediate a range of non-image forming responses to light. Melanopsin is a G protein coupled receptor (GPCR) and existing data suggest that it employs a membrane bound signalling cascade involving Gnaq/11 type G proteins. However, to date the precise identity of the Gα subunits involved in melanopsin phototransduction remains poorly defined. Here we show that Gnaq, Gna11 and Gna14 are highly co-expressed in pRGCs of the mouse retina. Furthermore, using RNAi based gene silencing we show that melanopsin can signal via Gnaq, Gna11 or Gna14 in vitro, and demonstrate that multiple members of the Gnaq/11 subfamily, including Gna14 and at least Gnaq or Gna11, can participate in melanopsin phototransduction in vivo and contribute to the pupillary light responses of mice lacking rod and cone photoreceptors. This diversity of G protein interactions suggests additional complexity in the melanopsin phototransduction cascade and may provide a basis for generating the diversity of light responses observed from pRGC subtypes.

Gαs regulates the post-endocytic sorting of G protein-coupled receptors.

The role of Gαs in G protein-coupled receptor (GPCR) signalling at the cell surface is well established. Recent evidence has revealed the presence of Gαs on endosomes and its capacity to elicit GPCR-promoted signalling from this intracellular compartment. Here, we report an unconventional role for Gαs in the endocytic sorting of GPCRs to lysosomes. Cellular depletion of Gαs specifically delays the lysosomal degradation of GPCRs by disrupting the transfer of GPCRs into the intraluminal vesicles (ILVs) of multivesicular bodies. We show that Gαs interacts with GPCR-associated binding protein-1 (GASP1) and dysbindin, two key proteins that serve as linkers between GPCRs and the endosomal-sorting complex required for transport (ESCRT) machinery involved in receptor sorting into ILVs. Our findings reveal that Gαs plays a role in both GPCR signalling and trafficking pathways, providing another piece in the intertwining molecular network between these processes.

Melanoma patients in a phase I clinic: molecular aberrations, targeted therapy and outcomes.

BACKGROUND: The purpose of the study was to assess the outcome of patients with advanced melanoma treated with matched molecularly targeted therapy. PATIENTS AND METHODS: We reviewed 160 consecutive patients with metastatic melanoma treated in the phase I program (N = 35 protocols). Treatment was considered to be 'matched' (N = 84) if at least one drug in the regimen was known to inhibit the functional activity of at least one of the patient's mutations. RESULTS: Of 160 patients, 134 (83.7%) had adequate tissue for molecular analysis; 69% (110 of 160) had ≥1 mutation: 61.2% (82 of 134), BRAF; 20.7% (23 of 111), NRAS; 2.6% (2 of 77), KIT; 2.3% (1 of 44), KRAS; 20% (1 of 5), GNAQ; 11.1% (1 of 9), P53 and 2.6% (1 of 39), coexisting mutations in BRAF and PIK3CA. Eighty-four patients (52.4%) were treated with matched-targeted agents, most of whom had BRAF mutations (N = 74). Twenty-six percent of patients (41 of 160) achieved a complete or partial remission (CR/PR) [40% (34 of 84)) on a matched phase I protocol versus 9.2% (7 of 76) for those on a non-matched study (P ≤ 0.0001)]. The median progression-free survival (PFS) (95% CI) was longer for patients treated on a matched phase I trial than on their prior first standard treatment [5.27 (4.10, 6.44) versus 3.10 (1.92, 4.28) months, P = 0.023], but not on non-matched phase I treatment. Multivariable analysis showed that matched therapy was an independent predictor of higher CR/PR rates, prolonged PFS and survival. CONCLUSIONS: For melanoma patients, especially those with BRAF mutations, administering molecularly matched agents can be associated with better outcomes, including longer PFS compared with their first-line systemic therapy.

Early endothelial damage and increased colonic vascular permeability in the development of experimental ulcerative colitis in rats and mice.

The role of endothelial damage and increased vascular permeability (VP) in the pathogenesis of ulcerative colitis (UC) has not been investigated. We examined using functional, morphologic, and molecular biologic studies whether and to what extent the endothelial barrier dysfunction precedes enhanced epithelial permeability (EP) and the development of mucosal lesions during the early stages of experimental UC. We showed that in rats with iodoacetamide (IA)-induced UC increased colonic VP occurs early (ie, 2.6-fold increase at 15 min, P<0.01) preceding changes in epithelial barrier permeability. EP was unchanged at 15 and 30 min after IA administration and was increased 1.9-fold at 1 h and 6.7-fold at 2 h (both P<0.001) after IA. In the dextran sodium sulfate-induced slowly developing UC, colonic VP was significantly increased in 2 days (P<0.05) and EP only in 4 days (P<0.05). Mucosal endothelial injury led to hypoxia (P<0.05) of colonic surface epithelial cells 30 min after IA administration that was associated with increased expressions of transcription factors hypoxia-inducible factor-1α and early growth response-1. Electron and light microscopy demonstrated areas of colonic mucosa with perivascular edema covered by intact layer of surface epithelial cells in both rat and mouse models of UC. This is the first demonstration in four models of UC that endothelial damage, increased colonic VP, perivascular edema, and epithelial hypoxia precede epithelial barrier dysfunction that is followed by erosions, ulceration, and inflammation in UC.

Propranolol modulates the collateral vascular responsiveness to vasopressin via a G(α)-mediated pathway in portal hypertensive rats.

Gastro-oesophageal variceal haemorrhage is one of the most dreadful complications of portal hypertension and can be controlled with vasoconstrictors. Nevertheless, sympathetic tone abnormality and vascular hyporesponsiveness in portal hypertension may impede the haemostatic effects of vasoconstrictors. Propranolol, a ß-blocker binding the G-protein-coupled adrenoceptor, is a portal hypotensive agent. However, whether propranolol influences the collateral vasoresponse is unknown. Portal hypertension was induced by PVL (portal vein ligation) in Sprague-Dawley rats. In an acute study with an in situ perfusion model, the collateral responsiveness to AVP (arginine vasopressin) was evaluated with vehicle, propranolol (10 µmol/l), propranolol plus suramin (100 µmol/l, a G(α) inhibitor) or suramin pre-incubation. G(α) mRNA expression in the splenorenal shunt, the most prominent intra-abdominal collateral vessel, was measured. In the chronic study, rats received DW (distilled water) or propranolol (10 mg x kg(-1) of body weight x day(-1)) for 9 days. Then the concentration-response relationship of AVP and G(α) mRNA expression were assessed. Propranolol pre-incubation elevated the perfusion pressure changes of collaterals in response to AVP, which was inhibited by suramin. The splenorenal shunt G(αq) and G(α11) mRNA expression were enhanced by propranolol. The group treated with propranolol plus suramin had a down-regulation of G(α11) as compared with the propranolol group. Chronic propranolol treatment reduced mean arterial pressure, PP (portal pressure) and the perfusion pressure changes of collaterals to AVP. G(αs) expression was up-regulated. In conclusion, propranolol pre-incubation enhanced the portal-systemic collateral AVP responsiveness in portal hypertensive rats, which was related to G(αq) and G(α11) up-regulation. In contrast, the attenuated AVP responsiveness by chronic propranolol treatment was related to G(αs) up-regulation. The G(α) signalling pathway may be a therapeutic target to control variceal bleeding and PP in portal hypertension.

Antagonist minigenes identify genes regulated by parathyroid hormone through G protein-selective and G protein co-regulated mechanisms in osteoblastic cells.

Parathyroid hormone (PTH) is the major hormone regulating bone remodeling. Binding of PTH to the PTH1 receptor (PTH1R), a heterotrimeric G protein coupled receptor (GPCR), can potentially trigger multiple signal transduction pathways mediated through several different G proteins. In this study, we employed G protein antagonist minigenes inhibiting Gα(s), Gα(q) or Gα12 to selectively dissect out which of these G proteins were responsible for effects of PTH(1-34) in targeted signaling and osteogenesis arrays consisting of 159 genes. Among the 32 genes significantly regulated by 24h PTH treatment in UMR-106 osteoblastic cells, 9 genes were exclusively regulated through G(s), 6 genes were solely mediated through G(q), and 3 genes were only controlled through G12. Such findings support the concept that there is some absolute specificity in downstream responses initiated at the G protein level following binding of PTH to the PTH1R. On the other hand, 6 PTH-regulated genes were regulated by both G(s) and G(q), 3 genes were regulated by both G(s) and G12, and 3 genes were controlled by G(s), G(q) and G12. These findings indicate potential overlapping or sequential interactions among different G protein-mediated pathways. In addition, two PTH-regulated genes were not regulated through any of the G proteins examined, suggesting that additional signaling mechanisms may be involved. Selectivity was largely maintained over a 2-48-hour time period. The minigene effects were mimicked by downstream inhibitors. The dissection of the differential effects of multiple G protein pathways on gene regulation provides a more complete understanding of PTH signaling in osteoblastic cells.