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Calcium sensing receptors (CaSR) interact with 14-3-3 binding proteins at a carboxyl terminal arginine-rich motif. Mutations identified in patients with familial hypocalciuric hypercalcemia, autosomal dominant hypocalcemia, pancreatitis or idiopathic epilepsy support the functional importance of this motif. We combined total internal reflection fluorescence microscopy and biochemical approaches to determine the mechanism of 14-3-3 protein regulation of CaSR signaling. Loss of 14-3-3 binding caused increased basal CaSR signaling and plasma membrane levels, and a significantly larger signaling-evoked increase in plasma membrane receptors. Block of core glycosylation with tunicamycin demonstrated that changes in plasma membrane CaSR levels were due to differences in exocytic rate. Western blotting to quantify time-dependent changes in maturation of expressed wt CaSR and a 14-3-3 protein binding-defective mutant demonstrated that signaling increases synthesis to maintain constant levels of the immaturely and maturely glycosylated forms. CaSR thus operates by a feed-forward mechanism, whereby signaling not only induces anterograde trafficking of nascent receptors but also increases biosynthesis to maintain steady state levels of net cellular CaSR. Overall, these studies suggest that 14-3-3 binding at the carboxyl terminus provides an important buffering mechanism to increase the intracellular pool of CaSR available for signaling-evoked trafficking, but attenuates trafficking to control the dynamic range of responses to extracellular calcium. 相似文献
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Adinda Vanommeslaeghe Ivan Meeus Gerda Cnops Tim Vleugels Martine Merchiers Barbara Duquenne Isabel Roldán-Ruiz Guy Smagghe 《Arthropod-Plant Interactions》2018,12(3):339-349
Red clover (Trifolium pratense) is an important forage crop in temperate regions. However, the seed yield in red clover, especially in tetraploid cultivars, constrains the commercial success of this crop. The relationship between seed yield and several flower and inflorescence characteristics has been investigated previously, but up to now no clear link has been identified. The central questions in this article are as follows: (1) Whether nectar production and composition are correlated with seed yield? (2) Which is the main pollinator found on red clover in Flanders? (3) Whether pollinator preferences can explain differences between high and low seed-yielding cultivars and genotypes? We found that Bombus pascuorum was the most abundant pollinator on red clover in the region considered. Nectar volume, nectar composition or pollinator preference did not explain the variation in seed yield between genotypes, nor between diploid and tetraploid cultivars. To explain seed yield differences among red clover genotypes and ploidy levels better, we believe that plant-related characteristics like problems with meiosis, low pollen or seed viability or embryo abortion need to be investigated. 相似文献
76.
Serafina Salvati Massimo Sanchez Lorenzo Malvezzi Campeggi †Gerda Suchanek ‡Helene Breitschop ‡Hans Lassmann 《Journal of neurochemistry》1996,67(4):1744-1750
Abstract: Our previous work showed an early development of behavioral reflexes in rats whose mothers had been fed, during pregnancy and lactation, a lipid fraction extracted from yeast grown on n -alkanes (which contain 50% odd-chain fatty acids) in comparison with controls fed a margarine diet. To clarify whether the observed changes might be linked to an early myelination, we have investigated mRNAs involved in myelin synthesis in the brains of offspring at 5 days of age by northern blot and in situ hybridization. Northern blot analysis showed that proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG) mRNAs were higher in animals on the lipid diet compared with controls. In situ hybridization with probes specific for PLP, myelin basic protein, and MOG mRNA showed significantly higher numbers of positive cells in test animals compared with controls in all brain regions. This study shows an acceleration of myelinogenesis induced by dietary lipids. These data can give a new insight in the therapeutical approaches involved to promote repair in demyelinating diseases. 相似文献
77.
Tatyana T. Ivanova-Nikolova Gerda E. Breitwieser 《The Journal of general physiology》1997,109(2):245-253
Receptor-mediated activation of heterotrimeric G proteins leading to dissociation of the Gα subunit
from Gβγ is a highly conserved signaling strategy used by numerous extracellular stimuli. Although Gβγ subunits
regulate a variety of effectors, including kinases, cyclases, phospholipases, and ion channels (Clapham, D.E., and
E.J. Neer. 1993. Nature (Lond.). 365:403–406), few tools exist for probing instantaneous Gβγ-effector interactions,
and little is known about the kinetic contributions of effectors to the signaling process. In this study, we used the
atrial muscarinic K+ channel, which is activated by direct interactions with Gβγ subunits (Logothetis, D.E., Y. Kurachi, J. Galper, E.J. Neer, and D.E. Clap. 1987. Nature (Lond.). 325:321–326; Wickman, K., J.A. Iniguez-Liuhi, P.A.
Davenport, R. Taussig, G.B. Krapivinsky, M.E. Linder, A.G. Gilman, and D.E. Clapham. 1994. Nature (Lond.). 366:
654–663; Huang, C.-L., P.A. Slesinger, P.J. Casey, Y.N. Jan, and L.Y. Jan. 1995. Neuron. 15:1133–1143), as a sensitive
reporter of the dynamics of Gβγ-effector interactions. Muscarinic K+ channels exhibit bursting behavior upon G
protein activation, shifting between three distinct functional modes, characterized by the frequency of channel
openings during individual bursts. Acetylcholine concentration (and by inference, the concentration of activated
Gβγ) controls the fraction of time spent in each mode without changing either the burst duration or channel gating within individual modes. The picture which emerges is of a Gβγ effector with allosteric regulation and an intrinsic “off” switch which serves to limit its own activation. These two features combine to establish exquisite channel sensitivity to changes in Gβγ concentration, and may be indicative of the factors regulating other Gβγ-modulated effectors. 相似文献
78.
Isolation and characterization of abscisic acid-deficient Arabidopsis mutants at two new loci 总被引:13,自引:1,他引:12
Karen M. Léon-Kloosterziel Marta Alvarez Gil Gerda J. Ruijs Steven E. Jacobsen Neil E. Olszewski Steven H. Schwartz Jan A.D. Zeevaart Maarten Koornneef 《The Plant journal : for cell and molecular biology》1996,10(4):655-661
Novel Arabidopsis mutants with lowered levels of endogenous abscisic acid (ABA) were isolated. These were selected in a screen for germination in the presence of the gibberellin biosynthesis inhibitor paclobutrazol. Another mutant was isolated in a screen for NaCl tolerance. The ABA-deficiency was caused by two monogenic, recessive mutations, aba2 and aba3 , that were both located on chromosome 1. The mutants showed a phenotype that is known to be characteristic for ABA-deficiency: a reduced seed dormancy and excessive water loss, leading to a wilty phenotype. Double mutant analysis, combining different aba mutations, indicated the leaky nature of the mutations. 相似文献
79.
Detailed description of four YAC contigs representing 17 Mb of chromosome 4 of Arabidopsis thaliana ecotype Columbia 总被引:2,自引:1,他引:1
Renate Schmidt Joanne West Gerda Cnops Karina Love Alma Balestrazzi Caroline Dean 《The Plant journal : for cell and molecular biology》1996,9(5):755-765
The detailed arrangement of 563 YAC clones comprising four contigs covering ~17 Mbp of chromosome 4 is presented. YAC clones were positioned relative to each other and to markers by taking into account marker and end fragment hybridization data and the sizes of all YAC clones. This analysis made it possible to estimate physical distances between the majority of chromosome 4 markers. It also identified a relatively large number of YAC clones containing chimaeric inserts. The YAC contig map of the Columbia ecotype presents an important resource for map-based cloning experiments, rapid mapping of DNA sequences and large-scale genomic sequencing programs. 相似文献
80.
A population of Rumex obtusifolius L. seeds imbibed for 24 h at 25°C exhibits a sigmoid logarithmic fluence-response relationship for stimulation of germination by red light (R), 11.0 μmol m−2 being necessary for 50% of the response. After 24 h imbibition at 35°C the fluence-response relationship for stimulation of germination by R is biphasic. For 50% response the very sensitive phase (very low fluence-response) requires 4.7 − 10−2 μmol m−2 whereas the less sensitive phase (low fluence-response) requires 4.0 μmol m2 . A few seconds of far-red light (FR) satisfies the germination requirement of the sensitive seeds after 24 h at 35°C. However, a longer period of FR (2 h) results in low germination. The fluence-response relationship for induction of these seeds by R is sigmoid, 4.8 μmol m−2 being necessary for 50% response, demonstrating that 2 h FR desensitizes the sensitive proportion of the seed population induced by 24 h at 35°C. A proportion of the seed population can be further sensitized by 60 min at 35°C following this desensitization. 相似文献