c-Cbl mediates ubiquitination, degradation, and down-regulation of human protease-activated receptor 2

Mechanisms that arrest G-protein-coupled receptor (GPCR) signaling prevent uncontrolled stimulation that could cause disease. Although uncoupling from heterotrimeric G-proteins, which transiently arrests signaling, is well described, little is known about the mechanisms that permanently arrest signaling. Here we reported on the mechanisms that terminate signaling by protease-activated receptor 2 (PAR(2)), which mediated the proinflammatory and nociceptive actions of proteases. Given its irreversible mechanism of proteolytic activation, PAR(2) is a model to study the permanent arrest of GPCR signaling. By immunoprecipitation and immunoblotting, we observed that activated PAR(2) was mono-ubiquitinated. Immunofluorescence indicated that activated PAR(2) translocated from the plasma membrane to early endosomes and lysosomes where it was degraded, as determined by immunoblotting. Mutant PAR(2) lacking intracellular lysine residues (PAR(2)Delta14K/R) was expressed at the plasma membrane and signaled normally but was not ubiquitinated. Activated PAR(2) Delta14K/R internalized but was retained in early endosomes and avoided lysosomal degradation. Activation of wild type PAR(2) stimulated tyrosine phosphorylation of the ubiquitin-protein isopeptide ligase c-Cbl and promoted its interaction with PAR(2) at the plasma membrane and in endosomes in an Src-dependent manner. Dominant negative c-Cbl lacking the ring finger domain inhibited PAR(2) ubiquitination and induced retention in early endosomes, thereby impeding lysosomal degradation. Although wild type PAR(2) was degraded, and recovery of agonist responses required synthesis of new receptors, lysine mutation and dominant negative c-Cbl impeded receptor ubiquitination and degradation and allowed PAR(2) to recycle and continue to signal. Thus, c-Cbl mediated ubiquitination and lysosomal degradation of PAR(2) to irrevocably terminate signaling by this and perhaps other GPCRs.

In vitro assessment of the bioaccessibility of brominated flame retardants in indoor dust using a colon extended model of the human gastrointestinal tract

An in vitro colon extended physiologically based extraction test (CEPBET) which incorporates human gastrointestinal tract (GIT) parameters (including pH and chemistry, solid-to-fluid ratio, mixing and emptying rates) was applied for the first time to study the bioaccessibility of brominated flame retardants (BFRs) from the 3 main GIT compartments (stomach, small intestine and colon) following ingestion of indoor dust. Results revealed the bioaccessibility of γ-HBCD (72%) was less than that for α- and β-isomers (92% and 80% respectively) which may be attributed to the lower aqueous solubility of the γ-isomer (2 μg L−1) compared to the α- and β-isomers (45 and 15 μg L−1 respectively). No significant change in the enantiomeric fractions of HBCDs was observed in any of the studied samples. However, this does not completely exclude the possibility of in vivo enantioselective absorption of HBCDs, as the GIT cell lining and bacterial flora – which may act enantioselectively – are not included in the current CE-PBET model. While TBBP-A was almost completely (94%) bioaccessible, BDE-209 was the least (14%) bioaccessible of the studied BFRs. Bioaccessibility of tri-hepta BDEs ranged from 32–58%. No decrease in the bioaccessibility with increasing level of bromination was observed in the studied PBDEs.

On L2 Clustering and Resetting the Null Subject Parameter in L2 Spanish: Implications and Observations.

In this article, along with others, we take the position that the Null-Subject Parameter (NSP) (Chomsky 1981; Rizzi 1982) cluster of properties is narrower in scope than some originally contended. We test for the resetting of the NSP by English L2 learners of Spanish at the intermediate level, including poverty-of-the stimulus knowledge of the Overt Pronoun Constraint (Montalbetti 1984). Our participants are tested before and after five months' residency in Spain in an effort to see if increased amounts of native exposure are particularly beneficial for parameter resetting. Although we demonstrate NSP resetting for some of the L2 learners, our data essentially demonstrate that even with the advent of time/exposure to native input, there is no immediate gainful effect for NSP resetting.

Endogenous managerial compensation contracts in experimental quantity-setting duopolies

Given the ongoing debate on managerial compensation schemes, our paper offers empirical insights on the strategic choice of firms' owners over the terms of a managerial compensation contract, as a commitment device aiming at gaining competitive advantage in the product market. In a quantity setting duopoly we experimentally test whether firms' owners compensate their managers through contracts combining own profits either with revenues or with relative performance, and the resulting managerial behaviour in the product market. Prominent among our results is that firms' owners choose relative performance over profit revenue contracts more frequently. Further, firms' owners successfully induce a more aggressive behaviour by their managers in the market, by setting incentives which deviate from strict profit maximization.

Estrogens and thyroid hormone: Non-genomic effects are coupled to transcription.

Estrogens and thyroid hormones are regulators of important diverse physiological processes such as reproduction, thermogenesis, neural development, neural differentiation and cardiovascular functions. Both are ligands for receptors in the nuclear receptor superfamily, which act as ligand-dependent transcription factors, regulating transcription. However, estrogens and thyroid hormones also rapidly (within minutes or seconds) activate kinase cascades and calcium increases, presumably initiated at the cell membrane. We discuss the relevance of both modes of hormone action, including the membrane estrogen receptor, to physiology, with particular reference to lordosis behavior. We first showed that estrogen restricted to the membrane can, in fact, lead to subsequent increases in transcription from a consensus estrogen response element-based reporter in the neuroblastoma cell line, SK-N-BE(2)C. Using a novel hormonal paradigm, we also showed that the activation of protein kinase A, protein kinase C, mitogen activated protein kinase and increases in calcium were important in the ability of the membrane-limited estrogen to potentiate transcription. We discuss the source of calcium important in transcriptional potentiation. Since estrogens and thyroid hormones have common effects on neuroprotection, cognition and mood, we also hypothesized that crosstalk could occur between the rapid actions of thyroid hormones and the genomic actions of estrogens. In neural cells, we showed that triiodothyronine acting rapidly via MAPK can increase transcription by the nuclear estrogen receptor ERa from a consensus estrogen response element, possibly by the phosphorylation of the ERa. Novel mechanisms that link signals initiated by hormones from the membrane to the nucleus are physiologically relevant and can achieve neuroendocrine integration