Impaired defense mechanism against inflammation, hyperalgesia, and airway hyperreactivity in somatostatin 4 receptor gene-deleted mice.

We have shown that somatostatin released from activated capsaicin-sensitive nociceptive nerve endings during inflammatory processes elicits systemic anti-inflammatory and analgesic effects. With the help of somatostatin receptor subtype 4 gene-deleted mice (sst(4)(-/-)), we provide here several lines of evidence that this receptor has a protective role in a variety of inflammatory disease models; several symptoms are more severe in the sst(4) knockout animals than in their wild-type counterparts. Acute carrageenan-induced paw edema and mechanical hyperalgesia, inflammatory pain in the early phase of adjuvant-evoked chronic arthritis, and oxazolone-induced delayed-type hypersensitivity reaction in the skin are much greater in mice lacking the sst(4) receptor. Airway inflammation and consequent bronchial hyperreactivity elicited by intranasal lipopolysaccharide administration are also markedly enhanced in sst(4) knockouts, including increased perivascular/peribronchial edema, neutrophil/macrophage infiltration, mucus-producing goblet cell hyperplasia, myeloperoxidase activity, and IL-1beta, TNF-alpha, and IFN-gamma expression in the inflamed lung. It is concluded that during these inflammatory conditions the released somatostatin has pronounced counterregulatory effects through sst(4) receptor activation. Thus, this receptor is a promising novel target for developing anti-inflammatory, analgesic, and anti-asthmatic drugs.

Altered vesicular dopamine storage in Parkinson's disease: a premature demise.

Dopamine is a potentially toxic neurotransmitter that has long been speculated to contribute to the pathogenesis of Parkinson's disease (PD). Recent work has demonstrated the importance of proper storage of dopamine in vesicles to maintain dopamine homeostasis, thus protecting neurons from the detrimental effects of dopamine accumulation and breakdown in the cytosol. These studies suggest that factors which affect dopamine storage might increase the susceptibility of dopamine neurons to further environmental or genetic insults, exacerbating the neuronal degeneration that characterizes PD. This review seeks to revisit the pathogenicity of cytosolic dopamine and further address the critical role of neurotransmitter storage in dopamine-mediated neurotoxicity.

Abnormal localization of leucine-rich repeat kinase 2 to the endosomal-lysosomal compartment in lewy body disease.

Missense mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common causes of both familial and sporadic forms of Parkinson disease and are also associated with diverse pathological alterations. The mechanisms whereby LRRK2 mutations cause these pathological phenotypes are unknown. We used immunohistochemistry with 3 distinct anti-LRRK2 antibodies to characterize the expression of LRRK2 in the brains of 21 subjects with various neurodegenerative disorders and 7 controls. The immunoreactivity of LRRK2 was localized in a subset of brainstem-type Lewy bodies (LBs) but not in cortical-type LBs, tau-positive inclusions, or TAR-DNA-binding protein-43-positive inclusions. The immunoreactivity of LRRK2 frequently appeared as enlarged granules or vacuoles within neurons of affected brain regions, including the substantia nigra, amygdala, and entorhinal cortex in patients with Parkinson disease or dementia with LBs. The volumes of LRRK2-positive granular structures in neurons of the entorhinal cortex were significantly increased in dementia with LBs brains compared with age-matched control brains (p < 0.05). Double immunolabeling demonstrated that these LRRK2-positive granular structures frequently colocalized with the late-endosomal marker Rab7B and occasionally with the lysosomal marker, the lysosomal-associated membrane protein 2. These results suggest that LRRK2 normally localizes to the endosomal-lysosomal compartment within morphologically altered neurons in neurodegenerative diseases, particularly in the brains of patients with LB diseases.

Increased expression of the NR2A NMDA receptor subunit in the prefrontal cortex of rats reared in isolation.

A hypofunction of the N-methyl-D-aspartate (NMDA) receptor has been implicated in the pathophysiology of schizophrenia. Compelling evidence of altered NMDA receptor subunit expression in the schizophrenic brain has not, however, so far emerged. Rats reared in isolation exhibit several characteristics, including disturbed sensory gating, which resemble those seen in schizophrenia. To explore the possibility that NMDA receptor dysfunction may contribute to the behavioral and neurochemical consequences of rearing rats in isolation, we compared NMDA receptor subunit expression in brains of rats which were housed in isolation and which displayed a deficit in prepulse inhibition of the acoustic startle response with that of socially housed controls. An initial microarray analysis revealed a 1.26-fold increase in NR2A transcript in the prefrontal cortex, but not in the nucleus accumbens, of rats reared in isolation compared with those housed socially. In contrast, NR1, NR2B, NR2C, NR2D, NR3A, and NR3B subunit expression was unchanged in either brain area. In a second cohort of animals, in situ hybridization revealed increased NR2A mRNA expression in the medial prefrontal cortex, an observation that was substantiated by increased [(3)H]CGP39653 binding suggesting that NR2A receptor subunit protein expression was also elevated in the medial prefrontal cortex of the same animals. No changes in expression of NR1 or NR2B subunits were observed at both mRNA and protein level. Altered NR2A subunit expression in the medial prefrontal cortex of rats reared in isolation suggests that NMDA receptor dysfunction may contribute to the underlying pathophysiology of this preclinical model of aspects of schizophrenia.

Reduced vesicular storage of dopamine causes progressive nigrostriatal neurodegeneration.

The vesicular monoamine transporter 2 (VMAT2; SLC18A2) is responsible for packaging dopamine into vesicles for subsequent release and has been suggested to serve a neuroprotective role in the dopamine system. Here, we show that mice that express approximately 5% of normal VMAT2 (VMAT2 LO) display age-associated nigrostriatal dopamine dysfunction that ultimately results in neurodegeneration. Elevated cysteinyl adducts to L-DOPA and DOPAC are seen early and are followed by increased striatal protein carbonyl and 3-nitrotyrosine formation. These changes were associated with decreased striatal dopamine and decreased expression of the dopamine transporter and tyrosine hydroxylase. Furthermore, we observed an increase in alpha-synuclein immunoreactivity and accumulation and neurodegeneration in the substantia nigra pars compacta in aged VMAT2 LO mice. Thus, VMAT2 LO animals display nigrostriatal degeneration that begins in the terminal fields and progresses to eventual loss of the cell bodies, alpha-synuclein accumulation, and an L-DOPA responsive behavioral deficit, replicating many of the key aspects of Parkinson's disease. These data suggest that mishandling of dopamine via reduced VMAT2 expression is, in and of itself, sufficient to cause dopamine-mediated toxicity and neurodegeneration in the nigrostriatal dopamine system. In addition, the altered dopamine homeostasis resulting from reduced VMAT2 function may be conducive to pathogenic mechanisms induced by genetic or environmental factors thought to be involved in Parkinson's disease.

Reduced vesicular storage of dopamine exacerbates methamphetamine-induced neurodegeneration and astrogliosis.

The vesicular monoamine transporter 2 (VMAT2) controls the loading of dopamine (DA) into vesicles and therefore determines synaptic properties such as quantal size, receptor sensitivity, and vesicular and cytosolic DA concentration. Impairment of proper DA compartmentalization is postulated to underlie the sensitivity of DA neurons to oxidative damage and degeneration. It is known that DA can auto-oxidize in the cytosol to form quinones and other oxidative species and that this production of oxidative stress is thought to be a critical factor in DA terminal loss after methamphetamine (METH) exposure. Using a mutant strain of mice (VMAT2 LO), which have only 5-10% of the VMAT2 expressed by wild-type animals, we show that VMAT2 is a major determinant of METH toxicity in the striatum. Subsequent to METH exposure, the VMAT2 LO mice show an exacerbated loss of dopamine transporter and tyrosine hydroxylase (TH), as well as enhanced astrogliosis and protein carbonyl formation. More importantly, VMAT2 LO mice show massive argyrophilic deposits in the striatum after METH, indicating that VMAT2 is a regulator of METH-induced neurodegeneration. The increased METH neurotoxicity in VMAT2 LO occurs in the absence of any significant difference in basal temperature or METH-induced hyperthermia. Furthermore, primary midbrain cultures from VMAT2 LO mice show more oxidative stress generation and a greater loss of TH positive processes than wild-type cultures after METH exposure. Elevated markers of neurotoxicity in VMAT2 LO mice and cultures suggest that the capacity to store DA determines the amount of oxidative stress and neurodegeneration after METH administration.

Increased tau phosphorylation on mitogen-activated protein kinase consensus sites and cognitive decline in transgenic models for Alzheimer's disease and FTDP-17: evidence for distinct molecular processes underlying tau abnormalities.

Abnormal tau phosphorylation occurs in several neurodegenerative disorders, including Alzheimer's disease (AD) and frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17). Here, we compare mechanisms of tau phosphorylation in mouse models of FTDP-17 and AD. Mice expressing a mutated form of human tau associated with FTDP-17 (tau(V337M)) showed age-related increases in exogenous tau phosphorylation in the absence of increased activation status of a number of kinases known to phosphorylate tau in vitro. In a "combined" model, expressing both tau(V337M) and the familial amyloid precursor protein AD mutation APP(V717I) in a CT100 fragment, age-dependent tau phosphorylation occurred at the same sites and was significantly augmented compared to "single" tau(V337M) mice. These effects were concomitant with increased activation status of mitogen-activated protein kinase (MAPK) family members (extracellular regulated kinases 1 and 2, p38, and c-Jun NH(2)-terminal kinase) but not glycogen synthase kinase-3alphabeta or cyclin-dependent kinase 5. The increase in MAPK activation was a discrete effect of APP(V717I)-CT100 transgene expression as near identical changes were observed in single APP(V717I)-CT100 mice. Age-dependent deficits in memory were also associated with tau(V337M) and APP(V717I)-CT100 expression. The data reveal distinct routes to abnormal tau phosphorylation in models of AD and FTDP-17 and suggest that in AD, tau irregularities may be linked to processing of APP C-terminal fragments via specific effects on MAPK activation status.

Pathological changes in dopaminergic nerve cells of the substantia nigra and olfactory bulb in mice transgenic for truncated human alpha-synuclein(1-120): implications for Lewy body disorders.

Dysfunction of the 140 aa protein alpha-synuclein plays a central role in Lewy body disorders, including Parkinson's disease, as well as in multiple system atrophy. Here, we show that the expression of truncated human alpha-synuclein(1-120), driven by the rat tyrosine hydroxylase promoter on a mouse alpha-synuclein null background, leads to the formation of pathological inclusions in the substantia nigra and olfactory bulb and to a reduction in striatal dopamine levels. At the behavioral level, the transgenic mice showed a progressive reduction in spontaneous locomotion and an increased response to amphetamine. These findings suggest that the C-terminal of alpha-synuclein is an important regulator of aggregation in vivo and will help to understand the mechanisms underlying the pathogenesis of Lewy body disorders and multiple system atrophy.

GABA(B) receptors: structure and function.

In the basal ganglia the effects of gamma-aminobutyrate (GABA) are mediated by both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. Although the existence and widespread distribution in the CNS of the GABA(B) receptor had been established in the 1980s the field of GABA(B) research was revolutionized with the discovery that two related G-protein-coupled receptors (GPCRs) needed to dimerize to form the functional GABA(B) receptor at the cell surface. This finding lead to a number of studies of oligomerization in GPCRs and detailed pharmacological studies of the cloned receptors and their splice variants. Particular interest has focused on the proteins interacting with the receptor which may be important in mediating the longer term signalling effects of the receptor and modifying its cellular localization or physiology. The cloning of the GABA(B) receptors also lead to the identification of the first compounds interacting in an allosteric fashion with the receptor some of which may have therapeutic value. Most recently "knockouts" of both the GABA(B) subunits have been produced where in general as expected there is a loss of the majority of the inhibitory effects of the GABA(B) receptor.

Chronic stress accelerates learning and memory impairments and increases amyloid deposition in APPV717I-CT100 transgenic mice, an Alzheimer's disease model.

Although chronic stress is known to be linked with memory and other neurological disorders, little is known about the relationship between chronic stress and the onset or development of Alzheimer's disease (AD). In this study, we investigated the effects of long-term stress on the onset and severity of cognitive deficits and pathological changes in APPV717I-CT100 mice overexpressing human APP-CT100 containing the London mutation (V717I) after exposure to immobilization stress. We found that chronic immobilization stress accelerated cognitive impairments, as accessed by the Passive avoidance and the Social Transfer of Food Preference (STFP) tests. Moreover, the numbers and densities of vascular and extracellular deposits containing amyloid beta peptide (Abeta) and carboxyl-terminal fragments of amyloid precursor protein (APP-CTFs), which are pathologic markers of AD, were significantly elevated in stressed animals, especially in the hippocampus. Moreover, stressed animals, also showed highly elevated levels of neurodegeneration and tau phosphorylation and increased intraneuronal Abeta and APP-CTFs immunoreactivities in the hippocampus and in the entorhinal and piriform cortex. This study provides the first evidence that chronic stress accelerates the onset and severity of cognitive deficits and that these are highly correlated with pathological changes, which thus indicates that chronic stress may be an important contributor to the onset and development of AD.

Gene expression profiles of metabolic enzyme transcripts in Alzheimer's disease.

The successfully functioning brain is a heavy user of metabolic energy. Alzheimer's disease, in which cognitive faculties decline, may be due, at least in part, to metabolic insufficiency. Using microarray analysis and quantitative RT-PCR, the expression of mRNA transcripts involved in glucose metabolism was investigated in Alzheimer's diseased post-mortem human hippocampal samples. Of the 51 members of the glycolytic, tricarboxylic acid cycle, oxidative phosphorylation, and associated pathways investigated by qPCR, 15 were confirmed to be statistically significantly (p<0.05) down-regulated in Alzheimer's disease. This finding suggests that reductions in the levels of transcripts encoded by genes that participate in energy metabolism may be involved in Alzheimer's disease.

Localization of Parkinson's disease-associated LRRK2 in normal and pathological human brain.

Mutations in the LRRK2 gene cause autosomal dominant, late-onset parkinsonism, which presents with pleomorphic pathology including alpha-synucleopathy. To promote our understanding of the biological role of LRRK2 in the brain we examined the distribution of LRRK2 mRNA and protein in postmortem human brain tissue from normal and neuropathological subjects. In situ hybridization and immunohistochemical analysis demonstrate the expression and localization of LRRK2 to various neuronal populations in brain regions implicated in Parkinson's disease (PD) including the cerebral cortex, caudate-putamen and substantia nigra pars compacta. Immunofluorescent double labeling studies additionally reveal the prominent localization of LRRK2 to cholinergic-, calretinin- and GABA(B) receptor 1-positive, dopamine-innervated, neuronal subtypes in the caudate-putamen. The distribution of LRRK2 in brain tissue from sporadic PD and dementia with Lewy bodies (DLB) subjects was also examined. In PD brains, LRRK2 immunoreactivity localized to nigral neuronal processes is dramatically reduced which reflects the disease-associated loss of dopaminergic neurons in this region. However, surviving nigral neurons occasionally exhibit LRRK2 immunostaining of the halo structure of Lewy bodies. Moreover, LRRK2 immunoreactivity is not associated with Lewy neurites or with cortical Lewy bodies in sporadic PD and DLB brains. These observations indicate that LRRK2 is not a primary component of Lewy bodies and does not co-localize with mature fibrillar alpha-synuclein to a significant extent. The localization of LRRK2 to key neuronal populations throughout the nigrostriatal dopaminergic pathway is consistent with the involvement of LRRK2 in the molecular pathogenesis of familial and sporadic parkinsonism.

Immunological function in mice lacking the Rac-related GTPase RhoG.

RhoG is a low-molecular-weight GTPase highly expressed in lymphocytes that activates gene transcription and promotes cytoskeletal reorganization in vitro. To study the in vivo function of RhoG, we generated mice homozygous for a targeted disruption of the RhoG gene. Despite the absence of RhoG, the development of B and T lymphocytes was unaffected. However, there was an increase in the level of serum immunoglobulin G1 (IgG1) and IgG2b as well as a mild increase of the humoral immune response to thymus-dependent antigens. In addition, B- and T-cell proliferation in response to antigen receptor cross-linking was slightly increased. Although RhoG deficiency produces a mild phenotype, our experiments suggest that RhoG may contribute to the negative regulation of immune responses. The lack of a strong phenotype could indicate a functional redundancy of RhoG with other Rac proteins in lymphocytes.

Abundant tau filaments and nonapoptotic neurodegeneration in transgenic mice expressing human P301S tau protein.

The identification of mutations in the Tau gene in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) has made it possible to express human tau protein with pathogenic mutations in transgenic animals. Here we report on the production and characterization of a line of mice transgenic for the 383 aa isoform of human tau with the P301S mutation. At 5-6 months of age, homozygous animals from this line developed a neurological phenotype dominated by a severe paraparesis. According to light microscopy, many nerve cells in brain and spinal cord were strongly immunoreactive for hyperphosphorylated tau. According to electron microscopy, abundant filaments made of hyperphosphorylated tau protein were present. The majority of filaments resembled the half-twisted ribbons described previously in cases of FTDP-17, with a minority of filaments resembling the paired helical filaments of Alzheimer's disease. Sarkosyl-insoluble tau from brains and spinal cords of transgenic mice ran as a hyperphosphorylated 64 kDa band, the same apparent molecular mass as that of the 383 aa tau isoform in the human tauopathies. Perchloric acid-soluble tau was also phosphorylated at many sites, with the notable exception of serine 214. In the spinal cord, neurodegeneration was present, as indicated by a 49% reduction in the number of motor neurons. No evidence for apoptosis was obtained, despite the extensive colocalization of hyperphosphorylated tau protein with activated MAP kinase family members. The latter may be involved in the hyperphosphorylation of tau.

A novel neuronal-specific splice variant of Type I phosphatidylinositol 4-phosphate 5-kinase isoform gamma.

Type I PIPkins (phosphatidylinositol 4-phosphate 5-kinases) are the enzymes that catalyse the major cellular route of synthesis of PtdIns(4,5) P2, and three isoforms (alpha, beta and gamma) with several splice variants have been found to date. In the present paper, we describe the discovery of a novel splice variant of the gamma isoform, which we call PIPkin Igammac, and which is characterized by the inclusion of a 26-amino-acid insert near the C-terminus. Its transcript appears to be selectively expressed in brain, where it locates in the neurons of restricted regions, such as cerebellum, hippocampus, cortex and olfactory bulb, as indicated by in situ hybridization studies. Overexpression of two different catalytically inactive constructs of PIPkin Igammac in rat cerebellar granule cells causes a progressive loss of their neuronal processes, whereas equivalent kinase-dead versions of PIPkin Igammaa did not induce any such effect, suggesting the possible existence of a specific PtdIns(4,5) P2 pool synthesized by PIPkin Igammac, which is involved in the maintenance of some neuronal cellular processes.

Contrasting Effects of Raclopride and SCH 23390 on the Cellular Content of Preproenkephalin A mRNA in Rat Striatum: A Quantitative Non-radioactive In Situ Hybridization Study.

The effects of acute i.p. administration of selective dopamine (DA) receptor antagonists on the expression of preproenkephalin A (PPE A) mRNA was investigated in the adult rat striatum. Animals were injected with either (a) a selective D1 receptor antagonist SCH 23390 (0.25 mg/kg), (b) a selective D2 receptor antagonist raclopride (5 mg/kg), or (c) SCH 23388 (0.25 mg/kg), the (S)-enantiomer of SCH 23390. Control naive animals did not receive an injection. At specific time points following drug administration (1, 3 or 9 h), rats were killed and striatal tissue processed for in situ hybridization with an alkaline phosphatase-labelled oligonucleotide probe complementary to a portion of the rat PPE A cDNA. Treatment of rats with SCH 23388 did not affect the content of PPE A mRNA expressed by striatal cells at any time point. However, 1 h after SCH 23390 administration, a significant decrease in striatal PPE A mRNA was detected, reflected by a decrease in the cellular content of mRNA. No significant changes in PPE A mRNA were detected in raclopride-treated sections at this time point. In contrast, both 3 and 9 h after an injection of raclopride a significant increase in the cellular content of PPE A mRNA was detected in the striatum. No change in the cellular content of mRNA was detected in SCH 23390-treated rats at these two latter time points. Throughout the striatum approximately 46% of neurons were found to express PPE A mRNA, with the highest percentage of cells (55%) being detected in the mid-caudal striatum. No significant differences in striatal DA content were detected with any drug treatment using HPLC electrochemical detection methods. These results demonstrate that acute administration of the DA D1 and D2 receptor antagonists has contrasting effects on the cellular content of PPE A mRNA in the adult rat striatum. These effects may reflect changes in the rate of mRNA transcription which may be mediated by cAMP.

Comparative cellular distribution of GABAA and GABAB receptors in the human basal ganglia: immunohistochemical colocalization of the alpha 1 subunit of the GABAA receptor, and the GABABR1 and GABABR2 receptor subunits.

The GABA(B) receptor is a G-protein linked metabotropic receptor that is comprised of two major subunits, GABA(B)R1 and GABA(B)R2. In this study, the cellular distribution of the GABA(B)R1 and GABA(B)R2 subunits was investigated in the normal human basal ganglia using single and double immunohistochemical labeling techniques on fixed human brain tissue. The results showed that the GABA(B) receptor subunits GABA(B)R1 and GABA(B)R2 were both found on the same neurons and followed the same distribution patterns. In the striatum, these subunits were found on the five major types of interneurons based on morphology and neurochemical labeling (types 1, 2, 3, 5, 6) and showed weak labeling on the projection neurons (type 4). In the globus pallidus, intense GABA(B)R1 and GABA(B)R2 subunit labeling was found in large pallidal neurons, and in the substantia nigra, both pars compacta and pars reticulata neurons were labeled for both receptor subunits. Studies investigating the colocalization of the GABA(A) alpha(1) subunit and GABA(B) receptor subunits showed that the GABA(A) receptor alpha(1) subunit and the GABA(B)R1 subunit were found together on GABAergic striatal interneurons (type 1 parvalbumin, type 2 calretinin, and type 3 GAD neurons) and on neurons in the globus pallidus and substantia nigra pars reticulata. GABA(B)R1 and GABA(B)R2 were found on substantia nigra pars compacta neurons but the GABA(A) receptor alpha(1) subunit was absent from these neurons. The results of this study provide the morphological basis for GABAergic transmission within the human basal ganglia and provides evidence that GABA acts through both GABA(A) and GABA(B) receptors. That is, GABA acts through GABA(B) receptors, which are located on most of the cell types of the striatum, globus pallidus, and substantia nigra. GABA also acts through GABA(A) receptors containing the alpha(1) subunit on specific striatal GABAergic interneurons and on output neurons of the globus pallidus and substantia nigra pars reticulata.

Identification of cells expressing somatostatin receptor 2 in the gastrointestinal tract of Sstr2 knockout/lacZ knockin mice.

Somatostatin is found in neurons and endocrine cells in the gastrointestinal tract. The actions of somatostatin are mediated by a family of G-protein-coupled receptors that compose five subtypes (SSTR1-5), each of which is encoded by a separate gene. lacZ "knockin" mice, in which the reporter gene lacZ was engineered into the genomic locus of Sstr2 by gene targeting, were used to examine the expression pattern of Sstr2 and identify potential targets for neurally released and hormonal somatostatin in the gastrointestinal tract. In the body of the stomach, a large proportion of epithelial cells and subpopulations of myenteric neurons expressed Sstr2. Double- or triple-labeling with antisera to H(+)K(+)ATPase (to identify parietal cells) and/or histidine decarboxylase (to identify enterochromaffin-like [ECL] cells) combined with beta-galactosidase staining revealed that both parietal cells and ECL cells expressed Sstr2, and these two cell types accounted for almost all of the Sstr2-expressing epithelial cells. Somatostatin inhibits gastric acid secretion. The presence of SSTR2 on both parietal and ECL cells suggests that somatostatin acting on SSTR2 may reduce acid secretion by both acting directly on parietal cells and by reducing histamine release from ECL cells. In the small and large intestine, subpopulations of neurons in the myenteric and submucosal plexuses expressed Sstr2, and many of the Sstr2-expressing myenteric neurons also showed SSTR2(a) immunostaining. Most of Sstr2-expressing neurons in the myenteric plexus showed nitric oxide synthase (NOS) immunoreactivity. Previous studies have shown that NOS neurons are descending interneurons and anally projecting, inhibitory motor neurons. Thus, somatostatin acting at SSTR2 receptors on NOS neurons might modulate descending relaxation.

Expression of Fyn, a non-receptor tyrosine kinase in prefrontal cortex from patients with schizophrenia and its correlation with clinical onset.

Fyn is a member of the non-receptor tyrosine kinase family, which is known to be closely involved in signal transduction in neurons and has an important role in the development and organisation of the central nervous system. In order to explore the possible role of Fyn in schizophrenia, the expression of Fyn messenger RNA (mRNA) and protein were investigated in the postmortem prefrontal cortex of brains from normal and 'schizophrenic' cases. There was an increase in both total area Fyn mRNA signal (17.7%, P<0.05) and cellular mRNA content (15.7%, P<0.05) in the schizophrenic group relative to controls. In parallel the content of Fyn protein detected by immuno-autoradiography was also increased in the schizophrenic cases (21.8% P<0.05). In addition, the cellular Fyn mRNA signal was negatively correlated with the age of onset (r=-0.94, P=0.0026). These results suggest that an increase in Fyn expression may contribute to the pathophysiology of schizophrenia.

GPR105, a novel Gi/o-coupled UDP-glucose receptor expressed on brain glia and peripheral immune cells, is regulated by immunologic challenge: possible role in neuroimmune function.

We have recently shown that UDP-glucose, and some related UDP-sugars, are potent agonists of the novel G protein-coupled receptor GPR105 (recently re-named P2Y(14)). GPR105 is widely expressed throughout many brain regions and peripheral tissues of human and rodents, and couples to a pertussis toxin-sensitive G protein. To further characterise the role of GPR105, we demonstrate by immunohistochemistry with receptor-specific antiserum that GPR105 protein is widely distributed throughout the post mortem human brain where it is localised to glial cells, and specifically co-localises with astrocytes. Using quantitative RT-PCR we also show that GPR105 mRNA exhibits a restricted expression profile in an array of human cell lines and primary cells, with prominent expression detected in immune cells including neutrophils, lymphocytes, and megakaryocytic cells. To investigate the G protein selectivity of GPR105, we used chimeric Galpha subunits (Galpha(qi5), Galpha(qo5), and Galpha(qs5)) and an intracellular Ca(2+) mobilisation assay to demonstrate that GPR105 couples to Galpha subunits of the G(i/o) family but not to G(s) family proteins or to endogenous G(q/11) proteins in HEK-293 cells. Finally, we show that expression of GPR105 mRNA in the rat brain is up-regulated by immunologic challenge with lipopolysaccharide. Based on these observations, we propose that G(i/o)-coupled GPR105 might play an important role in peripheral and neuroimmune function in response to extracellular UDP-sugars.