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Heterodimer Consisting (heterodimer + consisting)
Selected AbstractsApis mellifera ultraspiracle: cDNA sequence and rapid up-regulation by juvenile hormoneINSECT MOLECULAR BIOLOGY, Issue 5 2004A. R. Barchuk Abstract Two hormones, 20-hydroxyecdysone (20E) and juvenile hormone (JH) are key regulators of insect development including the differentiation of the alternative caste phenotypes of social insects. In addition, JH plays a different role in adult honey bees, acting as a ,behavioural pacemaker'. The functional receptor for 20E is a heterodimer consisting of the ecdysone receptor and ultraspiracle (USP) whereas the identity of the JH receptor remains unknown. We have cloned and sequenced a cDNA encoding Apis mellifera ultraspiracle (AMUSP) and examined its responses to JH. A rapid, but transient up-regulation of the AMUSP messenger is observed in the fat bodies of both queens and workers. AMusp appears to be a single copy gene that produces two transcripts (,4 and ,5 kb) that are differentially expressed in the animal's body. The predicted AMUSP protein shows greater sequence similarity to its orthologues from the vertebrate,crab,tick,locust group than to the dipteran,lepidopteran group. These characteristics and the rapid up-regulation by JH suggest that some of the USP functions in the honey bee may depend on ligand binding. [source] Chemical Coding of GABAB Receptor-Immunoreactive Neurones in Hypothalamic Regions Regulating Body WeightJOURNAL OF NEUROENDOCRINOLOGY, Issue 1 2003M. Bäckberg Abstract ,-aminobutyric acid (GABA) interacts with hypothalamic neuronal pathways regulating feeding behaviour. GABA has been reported to stimulate feeding via both ionotropic GABAA and metabotropic GABAB receptors. The functional form of the GABAB receptor is a heterodimer consisting of GABAB receptor-1 (GABABR1) and GABAB receptor-2 (GABABR2) proteins. Within the heterodimer, the GABA-binding site is localized to GABABR1. In the present study, we used an antiserum to the GABABR1 protein in order to investigate the cellular localization of GABABR1-immunoreactive neurones in discrete hypothalamic regions implicated in the control of body weight. The colocalization of GABABR1 immunoreactivity with different chemical messengers that regulate food intake was analysed. GABABR1-immunoreactive cell bodies were found in the periventricular, paraventricular (PVN), supraoptic, arcuate, ventromedial hypothalamic, dorsomedial hypothalamic, tuberomammillary nuclei and lateral hypothalamic area (LHA). Direct double-labelling showed that glutamic acid decarboxylase (GAD)-positive terminals were in close contact with GABABR1-containing cell bodies located in all these regions. In the ventromedial part of the arcuate nucleus, GABABR1-immunoreactive cell bodies were found to contain neuropeptide Y, agouti-related peptide (AGRP) and GAD. In the ventrolateral part of the arcuate nucleus, GABABR1-immunoreactive cell bodies were shown to contain pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript. In the LHA, GABABR1 immunoreactivity was present in both melanin-concentrating hormone- and orexin-containing cell populations. In the tuberomammillary nucleus, GABABR1-immunoreactive cell bodies expressed histidine decarboxylase, a marker for histamine-containing neurones. In addition, GAD and AGRP were found to be colocalized in some nerve terminals surrounding GABABR1-immunoreactive cell bodies in the parvocellular part of the PVN. The results may provide a morphological basis for the understanding of how GABA regulates the hypothalamic control of food intake and body weight via GABAB receptors. [source] Megakaryocytes derived from human embryonic stem cells: a genetically tractable system to study megakaryocytopoiesis and integrin functionJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2 2006M. GAUR Summary.,Background:,The platelet fibrinogen receptor, a heterodimer consisting of integrin subunits ,IIb and ,3, is required for platelet aggregation, spreading, and hemostasis. Platelet agonists such as thrombin and adenosine diphosphate (ADP) lead to the activation of ,IIb,3, thereby enhancing its affinity and avidity for binding fibrinogen (inside-out signaling). Furthermore, fibrinogen binding to ,IIb,3 triggers cytoskeletal changes and granule release (outside-in signaling).Aim:,Genetic approaches to characterize the molecular pathways involved in ,IIb,3 signaling are not possible with anucleate blood platelets. Therefore, we have established an OP9 stromal cell co-culture system to generate megakaryocytes from human embryonic stem cells (hESCs).Results:,,IIb,3 activation, measured by soluble fibrinogen binding to hESC-derived megakaryocytes, /GPIb,+ cells, is readily detectable following stimulation with known platelet agonists. Dose,response curves for peptide agonists specific for the two platelet thrombin receptors, protease-activated receptor 1 (PAR1) and PAR4, show a relative responsiveness that mirrors that of human platelets, and sub-maximal ADP responses are augmented by epinephrine. Moreover, hESC-derived megakaryocytes undergo lamellipodia formation, actin filament assembly, and vinculin localization at focal adhesions when plated on a fibrinogen-coated surface, characteristic of ,IIb,3 outside-in signaling. Undifferentiated hESCs genetically modified by lentiviral infection can be cloned and maintained in an undifferentiated state and then differentiated into megakaryocytes capable of ,IIb,3 activation.Conclusion:,Using hESCs, we have developed a renewable source of human megakaryocytes, and a genetically tractable system for studying megakaryocytopoiesis and ,IIb,3 signaling in the native cellular environment. [source] AXL and AXR1 have redundant functions in RUB conjugation and growth and development in ArabidopsisTHE PLANT JOURNAL, Issue 1 2007Nihal Dharmasiri Summary Cullin-RING ubiquitin-protein ligases such as the Skp1, cullin, F-box protein (SCF) have been implicated in many growth and developmental processes in plants. Normal SCF function requires that the CUL1 subunit be post-translationally modified by related to ubiquitin (RUB), a protein related to ubiquitin. This process is mediated by two enzymes: the RUB-activating and RUB-conjugating enzymes. In Arabidopsis, the RUB-activating enzyme is a heterodimer consisting of AXR1 and ECR1. Mutations in the AXR1 gene result in a pleiotropic phenotype that includes resistance to the plant hormone auxin. Here we report that the AXL (AXR1-like) gene also functions in the RUB conjugation pathway. Overexpression of AXL in the axr1-3 background complements the axr1-3 phenotype. Biochemical analysis indicates that AXL overexpression restores CUL1 modification to the wild-type level, indicating that AXR1 and AXL have the same biochemical activity. Although the axl mutant resembles wild-type plants, the majority of axr1 axl-1 double mutants are embryo or seedling lethal. Furthermore, the axl-1 mutation reveals novel RUB-dependent processes in embryo development. We conclude that AXR1 and AXL function redundantly in the RUB conjugating pathway. [source] | |||||||||||||