The puzzles in B→ππB\to \pi\pi and πK \pi K decays: possible implications for R-parity violating supersymmetry

Recent experiments suggest that certain data of $B \to \pi\pi,\pi K$ decays are inconsistent with the standard model expectations. We try to explain the discrepancies with R-parity violating suppersymmetry. By employing the QCD factorization approach, we study these decays in the minimal supersymmetric standard model with R-parity violation. We show that R-parity violation can resolve the discrepancies in both $B \to \pi\pi$ and $B \to \pi K$ decays, and find that in some regions of parameter spaces all these requirements, including the CP averaged branching ratios and the direct CP asymmetries, can be satisfied. Furthermore, we have derived stringent bounds on relevant R-parity violating couplings from the latest experimental data, and some of these constraints are stronger than the existing bounds.Comment: 24 pages, 6 figures and 5 tables. Text revised. Final version to appear in PR

Polarizations in decays B_{u,d}\to VV and possible implications for R-parity violating SUSY

Recently BABAR and Belle have measured anomalous large transverse polarizations in some pure penguin $B \to VV$ decays, which might be inconsistent with the Standard Model expectations. We try to explore its implications for R-parity violating (RPV) supersymmetry. The QCD factorization approach is employed for the hadronic dynamics of B decays. We find that it is possible to have parameter spaces solving the anomaly. Furthermore, we have derived stringent bounds on relevant RPV couplings from the experimental data, which is useful for further studies of RPV phenomena.Comment: 26 pages, 12 eps figures. Typos corrected and references added. Final version to appear in PR

Apelin receptor homodimer-oligomers revealed by single-molecule imaging and novel G protein-dependent signaling

The apelin receptor (APJ) belongs to family A of the G protein-coupled receptors (GPCRs) and is a potential pharmacotherapeutic target for heart failure, hypertension, and other cardiovascular diseases. There is evidence APJ heterodimerizes with other GPCRs; however, the existence of APJ homodimers and oligomers remains to be investigated. Here, we measured APJ monomer-homodimer-oligomer interconversion by monitoring APJ dynamically on cells and compared their proportions, spatial arrangement, and mobility using total internal reflection fluorescence microscopy, resonance energy transfer, and proximity biotinylation. In cells with <0.3 receptor particles/μm2, approximately 60% of APJ molecules were present as dimers or oligomers. APJ dimers were present on the cell surface in a dynamic equilibrium with constant formation and dissociation of receptor complexes. Furthermore, we applied interference peptides and MALDI-TOF mass spectrometry to confirm APJ homo-dimer and explore the dimer-interfaces. Peptides corresponding to transmembrane domain (TMD)1, 2, 3, and 4, but not TMD5, 6, and 7, disrupted APJ dimerization. APJ mutants in TMD1 and TMD2 also decreased bioluminescence resonance energy transfer of APJ dimer. APJ dimerization resulted in novel functional characteristics, such as a distinct G-protein binding profile and cell responses after agonist stimulation. Thus, dimerization may serve as a unique mechanism for fine-tuning APJ-mediated functions

Scattering of scalar perturbations with cosmological constant in low-energy and high-energy regimes

We study the absorption and scattering of massless scalar waves propagating in spherically symmetric spacetimes with dynamical cosmological constant both in low-energy and high-energy zones. In the former low-energy regime, we solve analytically the Regge-Wheeler wave equation and obtain an analytic absorption probability expression which varies with $M\sqrt{\Lambda}$, where $M$ is the central mass and $\Lambda$ is cosmological constant. The low-energy absorption probability, which is in the range of $[0, 0.986701]$, increases monotonically with increase in $\Lambda$. In the latter high-energy regime, the scalar particles adopt their geometric optics limit value. The trajectory equation with effective potential emerges and the analytic high-energy greybody factor, which is relevant with the area of classically accessible regime, also increases monotonically with increase in $\Lambda$, as long $\Lambda$ is less than or of the order of $10^4$. In this high-energy case, the null cosmological constant result reduces to the Schwarzschild value $27\pi r_g^2/4$.Comment: 12 pages, 6 figure

Dual-agonist occupancy of orexin receptor 1 and cholecystokinin A receptor heterodimers decreases G-protein-dependent signaling and migration in the human colon cancer cell line HT-29

The orexin (OX1R) and cholecystokinin A (CCK1R) receptors play opposing roles in the migration of the human colon cancer cell line HT-29, and may be involved in the pathogenesis and pathophysiology of cancer cell invasion and metastasis. OX1R and CCK1R belong to family A of the G-protein-coupled receptors (GPCRs), but the detailed mechanisms underlying their functions in solid tumor development remain unclear. In this study, we investigated whether these two receptors heterodimerize, and the results revealed novel signal transduction mechanisms. Bioluminescence and Förster resonance energy transfer, as well as proximity ligation assays, demonstrated that OX1R and CCK1R heterodimerize in HEK293 and HT-29 cells, and that peptides corresponding to transmembrane domain 5 of OX1R impaired heterodimer formation. Stimulation of OX1R and CCK1R heterodimers with both orexin-A and CCK decreased the activation of Gαq, Gαi2, Gα12, and Gα13 and the migration of HT-29 cells in comparison with stimulation with orexin-A or CCK alone, but did not alter GPCR interactions with β-arrestins. These results suggest that OX1R and CCK1R heterodimerization plays an anti-migratory role in human colon cancer cells. [Abstract copyright: Copyright © 2017. Published by Elsevier B.V.