The orphan GPR50 receptor specifically inhibits MT1 melatonin receptor function through heterodimerization

One-third of the approximately 400 nonodorant G protein-coupled receptors (GPCRs) are still orphans. Although a considerable number of these receptors are likely to transduce cellular signals in response to ligands that remain to be identified, they may also have ligand-independent functions. Several members of the GPCR family have been shown to modulate the function of other receptors through heterodimerization. We show that GPR50, an orphan GPCR, heterodimerizes constitutively and specifically with MT(1) and MT(2) melatonin receptors, using biochemical and biophysical approaches in intact cells. Whereas the association between GPR50 and MT(2) did not modify MT(2) function, GPR50 abolished high-affinity agonist binding and G protein coupling to the MT(1) protomer engaged in the heterodimer. Deletion of the large C-terminal tail of GPR50 suppressed the inhibitory effect of GPR50 on MT(1) without affecting heterodimerization, indicating that this domain regulates the interaction of regulatory proteins to MT(1). Pairing orphan GPCRs to potential heterodimerization partners might be of clinical importance and may become a general strategy to better understand the function of orphan GPCRs.     

The role of the muscarinic system in regulating estradiol secretion varies during the estrous cycle: the hemiovariectomized rat model

There is evidence that one gonad has functional predominance. The present study analyzed the acute effects of unilateral ovariectomy (ULO) and blocking the cholinergic system, by injecting atropine sulfate (ATR), on estradiol (E₂) serum concentrations during the estrous cycle. The results indicate that ULO effects on E₂ concentrations are asymmetric, vary during the estrous cycle, and partially depend on the cholinergic innervation.     

Presence of antibodies against cyclic citrullinated peptides in patients with 'rhupus': a cross-sectional study

'Rhupus' is a rare condition sharing features of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). If rhupus is a distinctive entity, an overlap between RA and SLE or a subset of SLE is currently debated. This study was performed to explore the prevalence of antibodies against cyclic citrullinated peptides (anti-CCP antibodies) in rhupus. Patients meeting American College of Rheumatology criteria for RA, SLE, or both were included. Clinical and radiographic features were recorded and sera were searched for anti-CCP antibodies, rheumatoid factor, antinuclear antibodies, anti-extractable nuclear antigens, and antibodies against double-stranded DNA (anti-dsDNA antibodies). Seven patients for each group were included. Clinical and serological features for RA or SLE were similar between rhupus and RA patients, and between rhupus and SLE patients, respectively. Values for anti-CCP antibodies obtained were significantly (p < 0.05) higher in RA (6/7) and rhupus (4/7) than in SLE patients (0/7) and healthy subjects (0/7). Our data support the possibility that rhupus is an overlap between RA and SLE, because highly specific autoantibodies for RA (anti-CCP) and for SLE (anti-dsDNA and anti-Sm) are detected in coexistence.     

Dual function of the long pentraxin PTX3 in resistance against pulmonary infection with Klebsiella pneumoniae in transgenic mice

The long pentraxin PTX3 is expressed during acute inflammation and appears to control nitric oxide (NO) and tumor necrosis factor (TNF)-alpha production. In the present study, the physiological function of PTX3 was investigated in a model of pulmonary infection caused by the Gram-negative bacterium Klebsiella pneumoniae. Transgenic mice expressing multiple copies of PTX3 under the control of its own promoter were used to assess lethality rates, bacterial counts and inflammatory indices following pulmonary infection of mice. Expression of PTX3 is enhanced during pulmonary infection in wild-type mice. In transgenic mice given a high inoculum, overt PTX3 expression was associated with faster lethality. Faster lethality correlated with enhanced nitrate in plasma, an inability of neutrophils to migrate to lung tissue and greater dissemination of bacteria to blood at 20h after infection. In contrast, transgenic PTX3 expression conferred protection to mice given lower pulmonary inocula. In the latter experiments, there was enhanced TNF-alpha production, greater neutrophil influx and phagocytosis of bacteria by migrated neutrophils. By controlling the production of TNF-alpha and NO, and depending on the intensity of the inflammatory response induced by a given inoculum, the expression of PTX3 may favor or disfavor the influx of neutrophils and the ability of the murine host to deal with pulmonary infection with K. pneumoniae. These experiments highlight the delicate balance that exists among the various mediators that control the inflammatory response and suggest that PTX3 is an essential part of the ability of a host to deal with bacterial infection.     

Structural remodeling of unweighted soleus myotendinous junction in monkey

This study describes the morphology of the soleus myotendinous junction (MTJ) in the Rhesus monkey. Ultrastructural observations revealed a structural complexity that probably reflects functional adaptations. We also studied ultrastructural modifications of the MTJ in response to 14 days of hypokinesia and microgravity (Bion 11 mission). The reduced limb mobility of the animals, placed in a safety seat aboard the satellite, induced a sarcolemmal remodeling that was enhanced by the microgravity conditions. Signs of MTJ remodeling such as alterations of contractile apparatus and myofilament-anchoring structures, T-tubule dilation, and autophagic vacuoles could be ascribed to the microgravity.     

Characterization of the bovine PRKAG3 gene: structure, polymorphism, and alternative transcripts

The bovine PRKAG3 gene encodes the AMPK gamma3 subunit, one isoform of the regulatory gamma subunit of the AMP-activated protein kinase (AMPK). The AMPK plays a major role in the regulation of energy metabolism and mutations affecting the genes encoding the gamma subunits have been shown to influence AMPK activity. The gamma3 subunit is involved in the regulation of AMPK activity in skeletal muscle and strongly influences glycogen metabolism. Glycogen content in muscle is correlated to meat quality in livestock because it influences postmortem maturation process and ultimate pH. Naturally occurring mutations in the porcine PRKAG3 gene highly affect meat quality by influencing glycogen content before slaughter. We present the characterization of the bovine PRKAG3 gene and a polymorphism analysis in three cattle breeds. Thirty-two SNPs were identified among which 13 are in the coding region, one is in the 3' UTR, and 18 are in the introns. Five of them change an amino acid in the PRKAG3 protein sequence. Allelic frequencies were determined in the three breeds considered, and mutant alleles affecting the coding sequence are found at a very low frequency. Alternative splicing sites were identified at two positions of the gene, introducing heterogeneity in the population of proteins translated from the gene.     

Neurogenin 2 is required for the development of ventral midbrain dopaminergic neurons

Proneural genes are crucial regulators of neurogenesis and subtype specification in many areas of the nervous system; however, their function in dopaminergic neuron development is unknown. We report that proneural genes have an intricate pattern of expression in the ventricular zone of the ventral midbrain, where mesencephalic dopaminergic neurons are generated. Neurogenin 2 (Ngn2) and Mash1 are expressed in the ventral midline, while Ngn1, Ngn2 and Mash1 are co-localized more laterally in the ventricular zone. Ngn2 is also expressed in an intermediate zone immediately adjacent to the ventricular zone at the ventral midline. To examine the function of these genes, we analyzed mutant mice in which one or two of these genes were deleted (Ngn1, Ngn2 and Mash1) or substituted (Mash1 in the Ngn2 locus). Our results demonstrate that Ngn2 is required for the differentiation of Sox2(+) ventricular zone progenitors into Nurr1(+) postmitotic dopaminergic neuron precursors in the intermediate zone, and that it is also likely to be required for their subsequent differentiation into tyrosine hydroxylase-positive dopaminergic neurons in the marginal zone. Although Mash1 normally has no detectable function in dopaminergic neuron development, it could partially rescue the generation of dopaminergic neuron precursors in the absence of Ngn2. These results demonstrate that Ngn2 is uniquely required for the development of midbrain dopaminergic neurons.     

Incisal orientation and biting efficiency

Broad-edged 'spatulate' upper and lower incisors are distinctive of catarrhines and platyrrhines who use them in various ways to peel fruits, remove bark, and strip leaves from branches. The incisors of modern humans not only control the bite size of foods during ingestion, but often grip items in a number of non-food related tasks. Such uses have long been implicated for Neandertals as well. Despite the evolutionary importance of incision and the fact that the incisors feature prominently in clinical dentistry (via orthodontic practices designed both to correct incisal misalignments and adjust their orientation), little is known about what affects their functional efficiency. Few mechanical analyses of incisal action have been published and none that seem to take note of the mechanisms of both fracture and friction at the tooth-food interface. Here, we modeled the incisal tip as a wedge, finding that the efficiency of biting foods that fracture elastically is strongly dependent on both the apex angle of the incisor and the coefficient of friction. Based on apex angle measurements from a small sample of human central incisors, the overall efficiency of upper central incisors is predicted to be greatest when the angle between the apex bisector and the direction of applied force is zero. However, this is complicated greatly by friction, particularly for the lower incisors. The analysis probably applies not only to the use of incisors by humans, but also to some extent to frugivorous primates. This model should clarify the mechanics behind incision and can provide a basic foundation upon which more advanced models can be built on in the future.