Membrane Conductances and Spectral Sensitivities of Pecten Photoreceptors

The electrical and spectral properties of depolarizing (proximal) and hyperpolarizing (distal) photoreceptors in the eye of the scallop, Pecten irradians, were examined. Both depolarizing and hyperpolarizing responses are associated with an increase in membrane conductance; in addition, the depolarizing response is characterized by a secondary decrease in conductance at light intensities which inactivate the response. Both responses can be reversed in polarity by applied current across the cell membrane. The depolarizing response has a reversal potential of approximately +10 mv, whereas the estimated reversal potential for the hyperpolarizing response is near -70 mv. The two responses have the same spectral sensitivity function, which agrees with a Dartnall nomogram for a rhodospin with a λ_max at 500 nm. It is suggested that the photochemical reactions produce different end products which give responses of opposite polarity in proximal and distal cells, or alternatively, that the reactions of the respective cell membranes to the same end product are different.     

Black Male Bellies and Red Female Throats: Color Changes with Breeding Status in a Threespine Stickleback

This paper provides the first report of black nuptial coloration on the ventral side for a population of threespine sticklebacks, Gasterosteus aculeatus, in Northern California. Black nuptial coloration was least intense during precourtship. Although the black coloration intensified during courtship, it was not a significant predictor of female choice and, unlike the red throat and blue eyes, was not inversely correlated with the number of female introductions necessary before spawning occurred. Black coloration was the most intense for males who successfully hatched embryos, supporting a parental-defense role late in the cycle. Unsuccessful fathers had more intensely colored red throats, blue eyes, and black bellies during most of the reproductive cycle than successful fathers. Some females in this study developed red coloration on their throat, although none to the intensity or distribution typical of a breeding male.     

Stickleback Males Increase Red Coloration and Courtship Behaviours in the Presence of a Competitive Rival

In species where females preferentially select the most colourful males, males may strategically invest in courtship and nuptial colour according to the presence of rivals. In this experimental study, we tested this in the three‐spined stickleback (Gasterosteus aculeatus) in which mature males exhibit carotenoid‐based red coloration to attract mates and defend their territories against male competitors. We challenged experimental males with either a red‐ornamented dummy male or a non‐ornamented dummy for five min per day in six‐d experimental trial, which was repeated twice during the breeding season. We found that the males presented with a coloured rival exhibited more frequent courtship behaviours (i.e. fanning and gluing) to females than those presented with a non‐coloured intruder during the second experimental trial. At the end of each trial, the experimental males also showed a significantly larger area of red coloration in the presence of a coloured intruder. Our findings suggest that male sticklebacks regulate mating effort according to the presence of competitive rivals by increasing their investment in costly signals when successful mating and territory defence is at risk.     

Receptor,Ligand and Transducer Contributions to Dopamine D2 Receptor Functional Selectivity

Functional selectivity (or biased agonism) is a property exhibited by some G protein-coupled receptor (GPCR) ligands, which results in the modulation of a subset of a receptor’s signaling capabilities and more precise control over complex biological processes. The dopamine D2 receptor (D₂R) exhibits pleiotropic responses to the biogenic amine dopamine (DA) to mediate complex central nervous system functions through activation of G proteins and β-arrestins. D₂R is a prominent therapeutic target for psychological and neurological disorders in which DA biology is dysregulated and targeting D₂R with functionally selective drugs could provide a means by which pharmacotherapies could be developed. However, factors that determine GPCR functional selectivity in vivo may be multiple with receptors, ligands and transducers contributing to the process. We have recently described a mutagenesis approach to engineer biased D₂R mutants in which G protein-dependent (^[Gprot]D₂R) and β-arrestin-dependent signaling (^[βarr]D₂R) were successfully separated (Peterson, et al. PNAS, 2015). Here, permutations of these mutants were used to identify critical determinants of the D₂R signaling complex that impart signaling bias in response to the natural or synthetic ligands. Critical residues identified in generating ^[Gprot]D₂R and ^[βarr]D₂R conferred control of partial agonism at G protein and/or β-arrestin activity. Another set of mutations that result in G protein bias was identified that demonstrated that full agonists can impart unique activation patterns, and provided further credence to the concept of ligand texture. Finally, the contributions and interplay between different transducers indicated that G proteins are not aberrantly activated, and that receptor kinase and β-arrestin activities are inextricably linked. These data provide a thorough elucidation of the feasibility and malleability of D₂R functional selectivity and point to means by which novel in vivo therapies could be modeled.     

Photoreceptors: unconventional ways of seeing

Animals perceive light typically by photoreceptor neurons assembled in eyes, but some also use non-eye photosensory neurons. Multidendritic neurons in the body wall of Drosophila larvae have now been shown to use an unconventional phototransduction mechanism to sense light.     

Substitution of 5-HT1A Receptor Signaling by a Light-activated G Protein-coupled Receptor

Understanding serotonergic (5-HT) signaling is critical for understanding human physiology, behavior, and neuropsychiatric disease. 5-HT mediates its actions via ionotropic and metabotropic 5-HT receptors. The 5-HT_1A receptor is a metabotropic G protein-coupled receptor linked to the G_i/o signaling pathway and has been specifically implicated in the pathogenesis of depression and anxiety. To understand and precisely control 5-HT_1A signaling, we created a light-activated G protein-coupled receptor that targets into 5-HT_1A receptor domains and substitutes for endogenous 5-HT_1A receptors. To induce 5-HT_1A-like targeting, vertebrate rhodopsin was tagged with the C-terminal domain (CT) of 5-HT_1A (Rh-CT_5-HT1A). Rh-CT_5-HT1A activates G protein-coupled inward rectifying K⁺ channels in response to light and causes membrane hyperpolarization in hippocampal neurons, similar to the agonist-induced responses of the 5-HT_1A receptor. The intracellular distribution of Rh-CT_5-HT1A resembles that of the 5-HT_1A receptor; Rh-CT_5-HT1A localizes to somatodendritic sites and is efficiently trafficked to distal dendritic processes. Additionally, neuronal expression of Rh-CT_5-HT1A, but not Rh, decreases 5-HT_1A agonist sensitivity, suggesting that Rh-CT_5-HT1A and 5-HT_1A receptors compete to interact with the same trafficking machinery. Finally, Rh-CT_5-HT1A is able to rescue 5-HT_1A signaling of 5-HT_1A KO mice in cultured neurons and in slices of the dorsal raphe showing that Rh-CT_5-HT1A is able to functionally compensate for native 5-HT_1A. Thus, as an optogenetic tool, Rh-CT_5-HT1A has the potential to directly correlate in vivo 5-HT_1A signaling with 5-HT neuron activity and behavior in both normal animals and animal models of neuropsychiatric disease.     

Evolutionary Significance of Photoreceptors: In Retrospect

This essay presents an updating of the author's theory thatthere are two major lines in the evolution of photoreceptors,one ciliary and the other rhabdomeric (microvillar). Argumentsare presented for rejecting a new and alternative theory ofSalvini-Plawen and Mayr (1977) that photoreceptors have arisenmany times, independently of one another, and that there areno major lines in the evolution of light-sensitive organelles.Arguments are also advanced against the theory of Vanfleterenand Coomans (1976) and others that microvillar photoreceptorsare induced by ciliary structures     

Trying to make sense of retromer

Retromer is a cytosolic protein complex which binds to post-Golgi organelles involved in the trafficking of proteins to the lytic compartment of the cell. In non-plant organisms, retromer mediates the recycling of acid hydrolase receptors from early endosomal (EE) compartments. In plants, retromer components are required for the targeting of vacuolar storage proteins, and for the recycling of endocytosed PIN proteins. However, there are contradictory reports as to the localization of the sorting nexins and the core subunit of retromer. There is also uncertainty as to the identity of the organelles from which vacuolar sorting receptors (VSRs) and endocytosed plasma membrane (PM) proteins are recycled. In this review we try to resolve some of these conflicting observations.     

Honey bees: Photoreceptors participating in orientation behaviour to light and gravity

Summary The ability of honey bees to dance compromise directions when confronted with conflicting light and gravity references was used to determine their spectral sensitivity. The action spectrum has peaks at 450 nm and 550 nm and thus indicates the contributions of the blue and green receptors of the bees' compound eyes. There is no obvious contribution from the UV receptors. The dance directions indicate that blue and yellow-green light is regarded as sunlight. UV light seems not to be so interpreted, though it clearly influences the bees' orientation to gravity, if it is polarized. This result is consistent with our earlier findings which demonstrated that the bees' 350 nm receptors are used as detectors of blue skylight rather than sunlight. Because the receptor contributions differ, there is a clear distinction between the sun compass behaviour apparent in the dances and the phototaxis responses observed in other contexts.Supported by the Deutsche Forschungsgemeinschaft, DFG-Schwerpunkt 322, 243     

重组人白介素6受体功能区片段的功能鉴定

用生物素标记重组人白介素6受体功能区片段rIL6R-28及其二联体蛋白rIL6R-53．竞争ELISA表明重组蛋白可以与配基IL-6特异结合．流式细胞术检测结果表明IL-6与生物素标记的重组蛋白所形成的复合物能够与7TD1细胞表面的gp130结合．而7TD1细胞生长分析则表明,重组蛋白可以增强IL-6对7TD1．细胞的生长刺激作用．     

Atypical Signaling and Functional Desensitization Response of MAS Receptor to Peptide Ligands

MAS is a G protein-coupled receptor (GPCR) implicated in multiple physiological processes. Several physiological peptide ligands such as angiotensin-(1–7), angiotensin fragments and neuropeptide FF (NPFF) are reported to act on MAS. Studies of conventional G protein signaling and receptor desensitization upon stimulation of MAS with the peptide ligands are limited so far. Therefore, we systematically analyzed G protein signals activated by the peptide ligands. MAS-selective non-peptide ligands that were previously shown to activate G proteins were used as controls for comparison on a common cell based assay platform. Activation of MAS by the non-peptide agonist (1) increased intracellular calcium and D-myo-inositol-1-phosphate (IP1) levels which are indicative of the activation of classical Gα_q-phospholipase C signaling pathways, (2) decreased Gα_i mediated cAMP levels and (3) stimulated Gα₁₂-dependent expression of luciferase reporter. In all these assays, MAS exhibited strong constitutive activity that was inhibited by the non-peptide inverse agonist. Further, in the calcium response assay, MAS was resistant to stimulation by a second dose of the non-peptide agonist after the first activation has waned suggesting functional desensitization. In contrast, activation of MAS by the peptide ligand NPFF initiated a rapid rise in intracellular calcium with very weak IP1 accumulation which is unlike classical Gα_q-phospholipase C signaling pathway. NPFF only weakly stimulated MAS-mediated activation of Gα₁₂ and Gα_i signaling pathways. Furthermore, unlike non-peptide agonist-activated MAS, NPFF-activated MAS could be readily re-stimulated the second time by the agonists. Functional assays with key ligand binding MAS mutants suggest that NPFF and non-peptide ligands bind to overlapping regions. Angiotensin-(1–7) and other angiotensin fragments weakly potentiated an NPFF-like calcium response at non-physiological concentrations (≥100 µM). Overall, our data suggest that peptide ligands induce atypical signaling and functional desensitization of MAS.     

Relative Sensitivities of Viruses to Different Species of Interferon

Some viruses were found to be more sensitive than others to the action of interferons from certain species of animals but less sensitive to interferons from other species. Vaccinia virus was the most sensitive to mouse and hamster interferons of five viruses tested, but the least sensitive of these five viruses to human, rabbit, and bat interferons. The relative sensitivities of the viruses to interferons were found to be characteristic for each of the species tested, with those closely related phylogenetically exhibiting similar patterns of relative interferon-induced virus resistance. The amount of synthetic double-stranded polynucleotide polyinosinic acid-polycytidylic acid required to induce resistance to each of the viruses in each of the cell species correlated with the interferon sensitivities of the viruses.     

T细胞抗原受体的结构与功能研究进展

T细胞抗原受体(T ceIl receptor,TCR)是T细胞表面关键的受体分子。TCR特异性地识别各种多肽抗原并通过胞内区ITAM磷酸化传递抗原刺激信号,进而引发T细胞的免疫效应。TCR的活性异常将会导致自身免疫病和免疫缺陷病的发生。对于TCR结构和功能的深入研究有助于我们更好地理解免疫反应的分子机理,从而为相关免疫疾病的预防和治疗提供重要的理论依据。该文对TCR的分类、基因重排机制、受体组装方式及其结构基础、TCR对抗原的识别以及活化机制等方面的研究成果进行了总结,综述了近几年来的最新研究进展。     

不同冬小麦品种对氮肥反应敏感性研究

以土垫旱耕人为土为供试土壤进行盆栽试验,在不同施氮水平条件下,以NR9405、9430、偃师9号、小偃6号陕229、西农2208、矮丰3号等7个冬小麦品种为材料,研究不同品种冬小麦对氮肥反应敏感性。结果表明：7个品种中,9430、西农2208、偃师9号和NR9405属于氮肥较敏感品种,小偃6号和矮丰3号属于氮肥敏感性较差品种,陕229居中。小偃6号对氮肥的反应敏感性最差,属于典型的对氮肥反应不敏感型品种。根据对不同品种干物质转移量、干物质转移效率和转移干物质对籽粒贡献率的分析,将供试品种分为两类：一类是在生长后期（开花至成熟）主要靠同化产物的继续大量形成和转移而影响籽粒产量,可称为“后期同化累积型”;另一类在生长后期则主要靠开花前干物质的转移而影响产量,可称为“后期物质转移型”。偃师9号、西农2208和9430属于比较典型的“后期同化累积型”,而小偃6号属于比较典型的“后期物质转移型”。将不同品种地上部分干物质、氮素累积对氮肥反应的敏感性对比分析后发现,“后期同化累积型”品种对氮肥反应相对敏感,“后期物质转移型”对氮肥反应的敏感性差,这种差异性可能与“后期同化累积型”在生长后期仍需继续从介质中吸收大量氮素,以满足同化需要,而“后期物质转移型”在生育后期主要靠花前吸收氮素转移和再分配以满足花后同化需要,从介质中吸收的氮素有限有关。