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GPCR-Kir channel signaling complexes: defining rules of engagement   总被引:2,自引:0,他引:2  
Ion channels and G protein-coupled receptors (GPCRs) are integral transmembrane proteins vital to a multitude of cell signaling and physiological functions. Members of these large protein families are known to interact directly with various intracellular protein partners in a dynamic and isoform-dependent manner, ultimately shaping their life cycle and signal output. The family of G protein-gated inwardly rectifying potassium channels (Kir3 or GIRK) expressed in brain, heart, and endocrine tissues were recently shown to stably associate with several different GPCRs, forming the basis of a macromolecular ion channel-GPCR signaling complex. The molecular determinants that mediate and maintain GPCR-Kir3 channel complexes are currently not well understood. Recent findings and emerging hypotheses on the assembly and stability of multiprotein GPCR-Kir channel signaling complexes are discussed, highlighting distinct mechanisms used by different Kir channel families. These protein-protein interaction processes are crucial in determining both the synaptic response times and the extent of GPCR "cross-talk" in Kir3-mediated inhibitory synaptic transmission.  相似文献   

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Genetic and cell biological analyses of sperm behavior in the female reproductive tract are providing important clues to the mechanisms of sperm competition, a form of sexual selection that is an important force that shapes reproductive behavior, physiology and morphology in a wide range of species.  相似文献   

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Varki  Ajit 《Glycobiology》1992,2(2):169
Fig. 1. The sialic acids. The nine-carbon backbone common toall sialic acids is shown. Natural substitutions described todate (at C4, C5, C7 C8, and C9,) are indicated. Additional diversityis generated by various types of glycosidic linkage (at R3)by generation of lactones (at C1 ), by dehydro forms (eliminatingR3), and anhydro forms diversity sialic acids neuraminic acids O-acetylation sialidase  相似文献   

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The early history of sialic acids   总被引:1,自引:0,他引:1  
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A fluorimetric assay has been developed for sialic acids in which sialic acids react with pyridoxamine to give fluorescent compounds in the presence of zinc ion and pyridine. This assay method is specific for unbound sialic acids and is a simple and sensitive procedure compared with the thiobarbituric acid assay of sialic acids.  相似文献   

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Hoverman JT  Relyea RA 《Oecologia》2007,154(3):551-560
Studies of inducible defenses have traditionally examined prey responses to one predator at a time. However, prey in nature encounter combinations of predators that should force them to produce phenotypic compromises. We examined how snails (Helisoma trivolvis) alter their phenotype in the presence of three different predator species that were presented alone and in pairwise combinations. When snails were exposed to each predator alone, they formed predator-specific defenses that reflected the differences in each predator’s foraging mode. When snails were exposed to pairwise combinations of predators, their phenotype was dependent on their ability to detect each predator, the risk posed by each predator, and the effectiveness of a given defense against each predator. Consequently, responses to combined predators were typically biased towards one of the predators in the pair. This suggests that prey facing combined predators do not form simple intermediate defenses and, as a result, may experience enhanced mortality risk when they encounter natural predator regimes.  相似文献   

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Diversity in the sialic acids.   总被引:16,自引:0,他引:16  
A Varki 《Glycobiology》1992,2(1):25-40
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It was found that Lactobacillus plantarum (strain BA 11) is able to synthesize sialic acids during its growth in MRS medium and that these molecules are located mainly on the surface of the bacterium. It was demonstrated also that the addition externally of N-acetylneuraminic acid in concentrations ranged from 10 to 500 microM into the culture medium, resulted to a substantial increase of the growth rate of the bacterium. Bacterial cultures in presence of added sialic acid (100 microM) for 24 hours, resulted to a two fold increase of the final bacterial mass compared to the cultures in absence of sialic acid. Maximum levels of sialic acids were observed after 48 h of bacterial growth. It was also found that neuraminic acids production was increased when Mn++ and Mg++ ions were added in the culture medium, while the addition of Co++, Ca++, Ba++, Cu++ and Ni++ had a negative effect.  相似文献   

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Rotaviruses are the leading cause of childhood diarrhea. The entry of rotaviruses into the host cell is a complex process that includes several interactions of the outer layer proteins of the virus with different cell surface molecules. The fact that neuraminidase treatment of the cells, or preincubation of the virus with sialic acid-containing compounds decrease the infectivity of some rotavirus strains, suggested that these viruses interact with sialic acid on the cell surface. The infectivity of some other rotavirus strains is not affected by neuraminidase treatment of the cells, and therefore they are considered neuraminidase-resistant. However, the current evidence suggests that even these neuraminidase-resistant strains might interact with sialic acids located in context different from that of the sialic acids used by the neuraminidase-sensitive strains. This review summarizes our current knowledge of the rotavirus-sialic acid interaction, its structural basis, the specificity with which distinct rotavirus isolates interact with sialic acid-containing compounds, and also the potential use of these compounds as therapeutic agents.  相似文献   

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Moist mucosal epithelial interfaces that are exposed to external environments are dominated by sugar epitopes, some of which (e.g., sialic acids) are involved in host defense. In this study, we determined the abundance and distribution of two sialic acids to assess differences in their availability to an exogenous probe in isolated mucins and mucous gels. We used atomic force microscopy to obtain force maps of human preocular mucous and purified ocular mucins by probing and locating the interactions between tip-tethered lectins Maackia amurensis and Sambucus nigra and their respective receptors, α-2,3 and α-2,6 N-acetylneuraminic (sialic) acids. The rupture force distributions were not affected by neighboring sugar-bearing molecules. Energy contours for both lectin-sugar bonds were fitted to a two-barrier model, suggesting a conformational change before dissociation. In contrast to data from purified mucin molecules, the preocular gels presented numerous large clusters (19,000 ± 4000 nm(2)) of α-2,6 sialic acids, but very few small clusters (2000 ± 500 nm(2)) of α-2,3 epitopes. This indicates that mucins, which are rich in α-2,3 sialic acids, are only partially exposed at the surface of the mucous gel. Microorganisms that recognize α-2,3 sialic acids will encounter only isolated ligands, and the adhesion of other microorganisms will be enhanced by large islands of neighboring α-2,6 sialic acids. We have unveiled an additional level of mucosal surface heterogeneity, specifically in the distribution of pro- and antiadhesive sialic acids that protect underlying epithelia from viruses and bacteria.  相似文献   

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