Expression of odorant-binding proteins in mouthpart palps of the desert locust Schistocerca gregaria.

Odorant-binding proteins (OBPs) are essential molecular elements of the insect chemosensory system, which is composed of the antennae and the mouthpart palps (maxillary and labial). In this study, we have analysed the expression and the sensilla specificity of 14 OBP subtypes in the palps of the desert locust Schistocerca gregaria. The locust palps comprise only a low number of sensilla basiconica but a high number of sensilla chaetica. Employing a variety of approaches, we found that only a subset of the antennal OBP repertoire was expressed in both palp types. These OBPs were previously shown to be expressed either in sensilla basiconica or sensilla chaetica of the antennae. Comparing the expression pattern in the two chemosensory organs revealed similarities and differences; most remarkably, two OBP subtypes, OBP6 and OBP8, were found in both sensilla types on palps, whereas on the antennae they were solely expressed in one sensillum type. Together, the data indicate a differential, but partly overlapping, expression of OBPs in the two sensilla types of the palps. The differences in the expression pattern of OBP subtypes between antennae and palps might be indicative for distinct functions of the OBPs in the two chemosensory organs.

Larval sensilla of the moth Heliothis virescens respond to sex pheromone components.

Female-released sex pheromones orchestrate the mating behaviour of moths. Recent studies have shown that sex pheromones not only attract adult males but also caterpillars. Single sensillum recordings revealed that larval antennal sensilla of the moth Heliothis virescens respond to specific sex pheromone components. In search for the molecular basis of pheromone detection in larvae, we found that olfactory sensilla on the larval antennae are equipped with the same molecular elements that mediate sex pheromone detection in adult male moths, including the Heliothis virescens receptors 6 (HR6) and HR13, as well as sensory neurone membrane protein 1 (SNMP1). Thirty-eight olfactory sensory neurones were identified in three large sensilla basiconica; six of these are considered as candidate pheromone responsive cells based on the expression of SNMP1. The pheromone receptor HR6 was found to be expressed in two cells and the receptor HR13 in three cells. These putative pheromone responsive neurones were accompanied by cells expressing pheromone-binding protein 1 (PBP1) and PBP2. The results indicate that the responsiveness of larval sensilla to female-emitted sex pheromones is based on the same molecular machinery as in the antennae of adult males.

The sensory neurone membrane protein SNMP1 contributes to the sensitivity of a pheromone detection system.

Male moths detect female-released sex pheromones with extraordinary sensitivity. The remarkable sensory ability is based on a cooperative interplay of pheromone binding proteins in the lymph of hair-like sensilla trichodea and pheromone receptors in the dendrites of sensory neurones. Here we examined whether in Heliothis virescens the so-called 'sensory neurone membrane protein 1' (SNMP1) may contribute to responsiveness to the pheromone component, (Z)-11-hexadecenal (Z11-16:Ald). By means of immunohistochemistry and in situ hybridization we demonstrated that SNMP1 is in fact present in cells expressing the Z11-16:Ald receptor HR13 and the dendrites of sensory neurones. To assess a possible function of SNMP1 we monitored the responsiveness of cell lines that expressed HR13 alone or the combination SNMP1/HR13 to stimulation with Z11-16:Ald by calcium imaging. It was found that SNMP1/HR13 cells were 1000-fold more sensitive to pheromone stimulation compared with HR13 cells. In contrast, cells that expressed HR13 and the non-neuronal SNMP2-type showed no change in pheromone sensitivity. Overall, our reconstitution experiments demonstrate that the presence of SNMP1 significantly increases the HR13-based responsiveness of cells to Z11-16:Ald, suggesting that SNMP1 also contributes to the response of the antennal neurones and thus to the remarkable sensitivity of the pheromone detection system.

Gastrointestinal chemosensation: chemosensory cells in the alimentary tract.

Sensing potentially beneficial or harmful constituents in the luminal content by specialized cells in the gastrointestinal mucosa is an essential prerequisite for governing digestive processes, initiating protective responses and regulating food intake. Until recently, it was poorly understood how the gastrointestinal tract senses and responds to nutrients and non-nutrients in the diet; however, the enormous progress in unraveling the molecular machinery underlying the responsiveness of gustatory cells in the lingual taste buds to these compounds has been an important starting point for studying intestinal chemosensation. Currently, the field of nutrient sensing in the gastrointestinal tract is evolving rapidly and is benefiting from the deorphanization of previously unliganded G-protein-coupled receptors which respond to important nutrients, such as protein degradation products and free fatty acids as well as from the FACS-assisted isolation of distinct cell populations. This review focuses on mechanisms and principles underlying the chemosensory responsiveness of the alimentary tract. It describes the cell types which might potentially contribute to chemosensation within the gut: cells that can operate as specialized sensors and transducers for luminal factors and which communicate information from the gut lumen by releasing paracrine or endocrine acting messenger molecules. Furthermore, it addresses the current knowledge regarding the expression and localization of molecular elements that may be part of the chemosensory machinery which render some of the mucosal cells responsive to constituents of the luminal content, concentrating on candidate receptors and transporters for sensing nutrients.

Altered expression of gustatory-signaling elements in gastric tissue of morbidly obese patients.

OBJECTIVE: Sensing of nutrients in the stomach is of crucial importance for the regulation of ingestive behavior especially in the context of metabolic dysfunctions such as obesity. Cells in the gastric mucosa with taste-signaling elements are considered as candidates for sensing the composition of ingested food and consequently modulate gastrointestinal processes. To assess whether obesity might have an impact on gastric chemosensory cells, gastric tissue samples from morbidly obese patients and normal-weight subjects were compared using a reverse transcriptase (RT)-PCR, qPCR and immunohistochemical approach. RESULTS: Analysis of biopsy tissue samples from human stomach revealed that transcripts for the taste-signaling elements, including the receptor T1R3 involved in the reception of amino acids and carbohydrates, the fatty acid receptor GPR120, the G protein gustducin, the effector enzyme PLCß2 and the ion channel TRPM5 are present in the human gastric mucosa and led to the visualization of candidate chemosensory cells in the stomach expressing gustatory marker molecules. RT-PCR and qPCR analyses indicated striking differences in the expression profiles of specimens from obese subjects compared with controls. For GPR120, gustducin, PLCß2 and TRPM5 the expression levels were increased, whereas for T1R3 the level decreased. Using TRPM5 as an example, we found that the higher expression level was associated with a higher number of TRPM5 cells in gastric tissue samples from obese patients. This remarkable change was accompanied by an increased number of ghrelin-positive cells. CONCLUSIONS: Our findings argue for a relationship between the amount of food intake and/or the energy status and the number of candidate chemosensory cells in the gastric mucosa.

A polymorphism in the gene encoding AdipoR1 affects olfactory recognition.

Polymorphisms in the gene encoding adiponectin receptor 1 (AdipoR1) are associated with insulin resistance, fatty liver, increased risk for type 2 diabetes and cardiovascular disease. AdipoR1 is expressed in the central nervous system and in the olfactory mucosa of mice and humans. We therefore hypothesized that a common polymorphism in AdipoR1 might alter olfactory function. We investigated a group of 222 healthy subjects (male: n = 147, female: n = 75) for olfactory recognition, and genotyped them for the polymorphism rs6666089 in the human AdipoR1 gene. This polymorphism has been previously shown to be associated with insulin resistance. Olfactory recognition was tested using standardized sniffing sticks, and parameters of glucose metabolism and serum adiponectin levels were assessed. We found a significant olfactory impairment in carriers of the AdipoR1 polymorphism rs6666089 (olfactory recognition: GG: 89.4 ± 1.2%, GA: 86.9 ± 1.4%, AA: 77.2 ± 4.8%, additive model, P = 0.0004, adjusted for age). Adiponectin levels had no impact on olfactory recognition. Fasting plasma glucose, fasting plasma insulin, body mass index and HbA1c did not differ between the genotype groups. In conclusion, the presence of a genetic variation in AdipoR1 is associated with decreased olfactory recognition in healthy subjects. Adiponectin signalling may have an important role in olfactory function and regulation of appetite.

Expression of a pheromone receptor in ovipositor sensilla of the female moth (Heliothis virescens).

Female moths release pheromones that influence various behavioral and physiological processes. The highly specific responses elicited by pheromones are mediated via specific chemosensory proteins, pheromone binding proteins and chemoreceptors, operating in the antennal sensory neurons. In Heliothis virescens, the response to the major pheromone component (Z)-11-hexadecenal (Z11-16:Al) is mediated by the pheromone binding protein PBP2 and the receptor type HR13. PCR experiments revealed that transcripts for relevant chemosensory molecules are also present in the abdomen suggesting an additional role. In the female, mRNA for HR13 as well as for the related PBP2 was found in the ovipositor tip and in an immunohistochemical analysis with a specific antiserum it was possible to visualize the receptor protein in distinct sensilla types surrounding the ovipositor tip. The expression of HR13 implies a chemosensory responsiveness of these sensilla types to pheromones possibly provided by PBP2. Due to the close vicinity of sensillar HR13 cells and pheromone producing cells in the ovipositor we propose that the HR13 cells might mediate abdominal responses to the emitted pheromones.

The sense of smell: reception of flavors.

The sensory and hedonic evaluation of most food-related flavors is mainly dependent on olfactory perception. The sense of smell is able to recognize and discriminate myriads of airborne molecules with great accuracy and sensitivity. The primary processes of odor perception are mediated by the chemosensory olfactory neurons in the nasal epithelium, which upon interaction with appropriate odorants elicit a chemo-electrical transduction process converting the chemical signal into electrical impulses. The encoded information is conveyed onto distinct glomeruli, inducing topographic activity patterns in the olfactory bulb. The emerging chemotopic maps are decoded in the olfactory cortex, leading to the perception of distinct flavors.

The sense of smell: multiple olfactory subsystems.

The mammalian olfactory system is not uniformly organized but consists of several subsystems each of which probably serves distinct functions. Not only are the two major nasal chemosensory systems, the vomeronasal organ and the main olfactory epithelium, structurally and functionally separate entities, but the latter is further subcompartimentalized into overlapping expression zones and projection-related subzones. Moreover, the populations of 'OR37' neurons not only express a unique type of olfactory receptors but also are segregated in a cluster-like manner and generally project to only one receptor-specific glomerulus. The septal organ is an island of sensory epithelium on the nasal septum positioned at the nasoplatine duct; it is considered as a 'mini-nose' with dual function. A specific chemosensory function of the most recently discovered subsystem, the so-called Grueneberg ganglion, is based on the expression of olfactory marker protein and the axonal projections to defined glomeruli within the olfactory bulb. This complexity of distinct olfactory subsystems may be one of the features determining the enormous chemosensory capacity of the sense of smell.

[Chediak-Higashi syndrome]. / Das Chediak-Higashi-Syndrom.

Chediak-Higashi syndrome (CHS) is a rare autosomal recessive lysosomal disorder characterized by frequent infections, oculocutaneous albinism, high bleeding tendency, and various neurological symptoms. Onset in early childhood mostly leads to lymphohistiocytic infiltration into multiple organs, which is usually lethal without bone marrow transplantation. The adult form of CHS has a milder course, no lymphohistiocytic infiltration, and is characterized by neurological manifestations such as polyneuropathy, parkinsonism, dementia, and ataxia. In young adults, a combination of these defects with oculocutaneous albinism or recurrent infections should bring CHS into consideration. Diagnosis is established by the presence of characteristic eosinophilic peroxidase-positive giant granules in leukocytes. This article summarizes current knowledge about the pathogenesis, clinical course, and therapy of CHS and reports on experience with two adult CHS patients.

Genes encoding candidate pheromone receptors in a moth (Heliothis virescens).

The remarkable responsiveness of male moths to female released pheromones is based on the extremely sensitive and selective reaction of highly specialized sensory cells in the male antennae. These cells are supposed to be equipped with male-specific receptors for pheromonal compounds, however, the nature of these receptors is still elusive. By using a combination of genomic sequence analysis and cDNA-library screening, we have cloned various cDNAs of the tobacco budworm Heliothis virescens encoding candidate olfactory receptors. A comparison of all identified receptor types not only highlighted their overall high degree of sequence diversity but also led to the identification of a small group of receptors sharing >40% identity. In RT-PCR analysis it was found that distinct members of this group were expressed exclusively in the antennae of male moths. In situ hybridization experiments revealed that the male-specific expression of these receptor types was confined to antennal cells located beneath sensillar hair structures (sensilla triochoidea), which have been shown to contain pheromone-sensitive neurons. Moreover, two-color double in situ-hybridization approaches uncovered that cells expressing one of these receptor types were surrounded by cells expressing pheromone-binding proteins, as expected for a pheromone-sensitive sensillum. These findings suggest that receptors like Heliothis receptor 14-16 (HR14-HR16) may render antennal cells responsive to pheromones.

A candidate olfactory receptor subtype highly conserved across different insect orders.

Candidate olfactory receptors of the moth Heliothis virescens were found to be extremely diverse from receptors of the fruitfly Drosophila melanogaster and the mosquito Anopheles gambiae, but there is one exception. The moth receptor type HR2 shares a rather high degree of sequence identity with one olfactory receptor type both from Drosophila (Dor83b) and from Anopheles (AgamGPRor7); moreover, in contrast to all other receptors, this unique receptor type is expressed in numerous antennal neurons. Here we describe the identification of HR2 homologues in two further lepidopteran species, the moths Antheraea pernyi and Bombyx mori, which share 86-88% of their amino acids. In addition, based on RT-PCR experiments HR2 homologues were discovered in antennal cDNA of the honey bee (Apis mellifera; Hymenoptera), the blowfly (Calliphora erythrocephala; Diptera) and the mealworm (Tenebrio molitor; Coleoptera). Comparison of all HR2-related receptors revealed a high degree of sequence conservation across insect orders. In situ hybridization of antennal sections from the bee and the blowfly support the notion that HR2-related receptors are generally expressed in a very large number of antennal cells. This, together with the high degree of conservation suggests that this unique receptor subtype may fulfill a special function in chemosensory neurons of insects.

Sense of smell: recognition and transduction of olfactory signals.

The primary processes in odour perception, i.e. recognition and transduction of olfactory stimuli, are mediated by the chemosensory olfactory neurons. Interaction of odorous compounds with suitable receptor proteins in the membrane of a subset of cells elicits chemo-electrical transduction pathways, including second messenger cascades and ion channels, that modulate the excitability of the sensory neurons, i.e. converting the chemical stimulus into electrical impulses. The encoded information is conveyed via the axons onto distinct glomeruli in the olfactory bulb. Olfactory sensory cells expressing the same receptor type are segregated spatially in a distinct zone of the nasal epithelium and converge their axons to one or a few distinct glomeruli. The emerging chemotopic maps are considered to be crucial for processing and encoding sensory information of olfactory stimuli.

Magnetic resonance cholangiopancreatography. The fine art of bilio-pancreatic imaging.

With the introduction of endoscopic retrograde cholangio-pancreatography in the early 1970s, gastroenterologists have a lot of diagnostic options in the biliopancreatic system to their disposal. Meanwhile, magnetic resonance cholangiopancreatography (MRCP) has become a competitive replacement for diagnostic ERCP with the advantage of avoiding complications related to endoscopic techniques. Mounting evidence suggests that both MRCP and MRI (magnetic resonance imaging) have a profound influence of diagnostic algorithms in a variety of hepatobiliary and pancreatic diseases.

Identity and expression pattern of chemosensory proteins in Heliothis virescens (Lepidoptera, Noctuidae).

Analyzing the chemosensory organs of the moth Heliothis virescens, three proteins belonging to the family of insect chemosensory proteins (CSPs) have been cloned; they are called HvirCSP1, HvirCSP2 and HvirCSP3. The HvirCSPs show about 50% identity between each other and 30-76% identity to CSPs from other species. Overall, they are rather hydrophilic proteins but include a conserved hydrophobic motif. Tissue distribution and temporal expression pattern during the last pupal stages were assessed by Northern blots. HvirCSP mRNAs were detected in various parts of the adult body with a particular high expression level in legs. The expression of HvirCSP1 in legs started early during adult development, in parallel with the appearance of the cuticle. HvirCSP1 mRNA was detectable five days before eclosion (day E-5), increased dramatically on day E-3 and remained at high level into adult life. The tissue distribution and the time course of appearance of HvirCSPs are in agreement with a possible role in contact chemosensation.

Identification of a nonmammalian Golf subtype: functional role in olfactory signaling of airborne odorants in Xenopus laevis.

Attempts to identify the Galpha subtypes in the two compartments of the olfactory system from Xenopus, which are supposed to be specialized for detecting aquatic and volatile odorous compounds, revealed that a Galpha(o1) subtype is characteristic for the "water nose," the lateral diverticulum, whereas a novel Galpha(s) subtype predominates in the "air nose," the medial diverticulum. The newly identified Galpha(s)-type is more closely related to Galpha(olf) of rat and human than to the known Galpha(s)-isoform of Xenopus; it is therefore considered the first identified nonmammalian Galpha(olf) subtype. Sequence comparison of Galpha(olf) from amphibia and mammals revealed a particular conservation within the alpha-helical domains, which are supposed to control the GDP/GTP-exchange rate. The selective expression of different Galpha subtypes in the two anatomically separated and functionally specialized nasal compartments parallels the expression of distinct classes of olfactory receptors. Moreover, biochemical analysis revealed that stimulation with appropriate odorous compounds elicits the formation of inositol trisphosphate in the lateral diverticulum. In contrast, cyclic adenosine monophosphate signals were induced in the medial diverticulum, and this response appears to be mediated by the novel Galpha(olf) subtype. The data indicate that olfactory sensory neurons in each of the nasal cavities are equipped not only with defined sets of receptor types but also with a distinct molecular machinery for the chemo-electrical transduction process.

Characteristic features and ligand specificity of the two olfactory receptor classes from Xenopus laevis.

Amphibia have two classes of olfactory receptors (ORs), class I (fish-like receptors) and class II (mammalian-like receptors). These two receptor classes correspond to the two classes identified in other vertebrates, and amphibians thus provide a unique opportunity to compare olfactory receptors of both classes in one animal species, without the constraints of evolutionary distance between different vertebrate orders, such as fish and mammals. We therefore identified the complete open reading frames of class I and class II ORs in Xenopus laevis. In addition to allowing a representative comparison of the deduced amino acid sequences between both receptor classes, we were also able to perform differential functional analysis. These studies revealed distinct class-specific motifs, particularly in the extracellular loops 2 and 3, which might be of importance for the interaction with odorants, as well as in the intracellular loops 2 and 3, which might be responsible for interactions with specific G-proteins. The results of functional expression studies in Xenopus oocytes, comparing distinct receptor types, support the idea that class I receptors are activated by water-soluble odorants, whereas class II receptors are activated by volatile compounds.

Identification of a third rat odorant-binding protein (OBP3).

From a rat olfactory epithelium cDNA library clones encoding a lipocalin were isolated with sequence identity to the previously described salivary-specific alpha-2u globulin and the N-terminal region of mouse odorant-binding proteins OBP-III and OBP-IV. In situ hybridization showed strong expression in nasal glands displaying a pattern equivalent to rat OBP1. Heterologously expressed protein was evaluated for its binding properties using spectroscopic approaches. The recombinant protein interacted with two fluorescent probes, 1-aminoanthracene (1-AMA) and 1,1'-bis(4-anilino-5-naphthalene)-sulfonic acid. 1-AMA binding was competed by several odorants with high affinity. The thermodynamic parameters of the protein-odorant interaction were determined using isothermal titration calorimetry. Due to its nasal expression and odorant-binding characteristics this protein was designated OBP3.

Detection and removal of an artefact fatty acid from the binding site of recombinant Bombyx mori pheromone-binding protein.

Recombinant Bombyx mori pheromone-binding protein (PBP), purified from an Escherichia coli expression system, has been found to contain (11Z)-octadecenoic acid (cis-vaccenic acid) as an artefact ligand. An efficient delipidation procedure is described to overcome what would appear to be a general problem with recombinant lepidopteran PBPs.