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71.
Varghese B Barriere H Carbone CJ Banerjee A Swaminathan G Plotnikov A Xu P Peng J Goffin V Lukacs GL Fuchs SY 《Molecular and cellular biology》2008,28(17):5275-5287
The ubiquitination of the receptor that mediates signaling induced by the polypeptide pituitary hormone prolactin (PRL) has been shown to lead to the degradation of this receptor and to the ensuing negative regulation of cellular responses to PRL. However, the mechanisms of PRL receptor (PRLr) proteolysis remain largely to be determined. Here we provide evidence that PRLr is internalized and primarily degraded via the lysosomal pathway. Ubiquitination of PRLr is essential for the rapid internalization of PRLr, which proceeds through a pathway dependent on clathrin and the assembly polypeptide 2 (AP2) adaptor complexes. Recruitment of AP2 to PRLr is stimulated by PRLr ubiquitination, which also is required for the targeting of already internalized PRLr to the lysosomal compartment. While mass spectrometry analysis revealed that both monoubiquitination and polyubiquitination (via both K48- and K63-linked chains) occur on PRLr, the results of experiments using forced expression of ubiquitin mutants indicate that PRLr polyubiquitination via K63-linked chains is important for efficient interaction of PRLr with AP2 as well as for efficient internalization, postinternalization sorting, and proteolytic turnover of PRLr. We discuss how specific ubiquitination may regulate early and late stages of endocytosis of PRLr and of related receptors to contribute to the negative regulation of the magnitude and duration of downstream signaling. 相似文献
72.
Blake C. Meyers Michael J. Axtell Bonnie Bartel David P. Bartel David Baulcombe John L. Bowman Xiaofeng Cao James C. Carrington Xuemei Chen Pamela J. Green Sam Griffiths-Jones Steven E. Jacobsen Allison C. Mallory Robert A. Martienssen R. Scott Poethig Yijun Qi Herve Vaucheret Olivier Voinnet Yuichiro Watanabe Detlef Weigel Jian-Kang Zhu 《The Plant cell》2008,20(12):3186-3190
73.
Yefimova MG Sow A Fontaine I Guilleminot V Martinat N Crepieux P Canepa S Maurel MC Fouchécourt S Reiter E Benzakour O Guillou F 《Biology of reproduction》2008,78(4):697-704
Transferrin is well known as an iron transport glycoprotein. Dimeric or tetrameric transferrin forms have recently been reported to modulate phagocytosis by human leukocytes. It is mainly synthesized by the liver, and also by other sources, such as Sertoli cells of the testis. Sertoli cells show a strong phagocytic activity toward apoptotic germ cells and residual bodies. Here, we provide evidence that purified human dimeric transferrin from commercial sources decreased residual body phagocytosis, unlike monomeric transferrin. The presence of iron appeared essential for dimeric transferrin inhibitory activity. Importantly, dimeric transferrin could be visualized by immunoblotting in Sertoli cell lysates as well as in culture media, indicating that dimeric transferrin could be physiologically secreted by Sertoli cells. By siRNA-mediated knockdown, we show that endogenous transferrin significantly inhibited residual body ingestion by Sertoli cells. These results are the first to identify dimeric transferrin in Sertoli cells and to demonstrate its implication as a physiological modulator of residual body phagocytosis by Sertoli cells. 相似文献
74.
75.
Christelle Boileau Johanne Martel-Pelletier Judith Caron Philippe Msika Georges B Guillou Caroline Baudouin Jean-Pierre Pelletier 《Arthritis research & therapy》2009,11(2):R41-9
Introduction
The aims of this study were, first, to investigate the in vivo effects of treatment with avocado/soybean unsaponifiables on the development of osteoarthritic structural changes in the anterior cruciate ligament dog model and, second, to explore their mode of action. 相似文献76.
William F. Schwindinger Lauren J. Murphree Mihalcik Kathryn E. Giger Kelly S. Betz Anna Maria Stauffer Joel Linden Denis Herve Janet D. Robishaw 《The Journal of biological chemistry》2010,285(39):29787-29796
The adenosine A2A receptor (A2AR) is increasingly recognized as a novel therapeutic target in Parkinson disease. In striatopallidal neurons, the G-protein αolf subtype is required to couple this receptor to adenylyl cyclase activation. It is now well established that the βγ dimer also performs an active role in this signal transduction process. In principal, sixty distinct βγ dimers could arise from combinatorial association of the five known β and 12 γ subunit genes. However, key questions regarding which βγ subunit combinations exist and whether they perform specific signaling roles in the context of the organism remain to be answered. To explore these questions, we used a gene targeting approach to specifically ablate the G-protein γ7 subtype. Revealing a potentially new signaling paradigm, we show that the level of the γ7 protein controls the hierarchial assembly of a specific G-protein αolfβ2γ7 heterotrimer in the striatum. Providing a probable basis for the selectivity of receptor signaling, we further demonstrate that loss of this specific G-protein heterotrimer leads to reduced A2AR activation of adenylyl cyclase. Finally, substantiating an important role for this signaling pathway in pyschostimulant responsiveness, we show that mice lacking the G-protein γ7 subtype exhibit an attenuated behavioral response to caffeine. Collectively, these results further support the A2AR G-protein αolfβ2γ7 interface as a possible therapeutic target for Parkinson disease. 相似文献
77.
78.
The application of light reflectance for estimating biomass concentration was investigated on oxidative chemostat culture of Saccharomyces cerevisiae. A correlation between light reflectance and dry weight was established for biomass concentrations from 0.5 to 10 g l–1. The light reflectance signal was stable during the course of chemostat culture and proved to be sensitive to slight but fast changes in biomass concentration following shift-up in dilution rate, acetate pulse or during an oscillation. On-line estimated biomass revealed a larger time window of the biological response during spontaneous oscillations and could be used to predict carbohydrate storage. 相似文献
79.
Claude Courties Roland Perasso Marie-Josèphe Chrétiennot-Dinet Manolo Gouy Laure Guillou Marc Troussellier 《Journal of phycology》1998,34(5):844-849
Ostreococcus tauri Courties et Chrétiennot-Dinet is the smallest described autotrophic eukaryote dominating the phytoplanktonic assemblage of the marine Mediterranean Thau lagoon (France). Its taxonomic position was partly elucidated from ultrastructure and high-pressure liquid chromatography (HLPC) pigment analysis. The sequence analysis of the 18S rDNA gene of O. tauri measured here is available in EMBL Nucleotide Sequence Database (accession number: Y15814) and allowed to clarify its phylogenetic position. O. tauri belongs to the Prasinophyceae and appears very close to Mantoniella, a typical scaly Prasinophyceae, morphologically very different from the naked and coccoid Ostreococcus. An electrophoretic analysis of O. tauri shows that the nucleus contains 10.20 mbp. This small genome, fragmented into 14 chromosomes ranging in size from 300 to 1500 kbp, confirms the minimalist characteristics of Ostreococcus tauri. 相似文献
80.
L. Catoire I. Braccini N. Bouchemal-Chibani L. Jullien C. Herve du Penhoat S. Perez 《Glycoconjugate journal》1997,14(8):935-943
Over the past decade molecular mechanics and molecular dynamics studies have demonstrated considerable flexibility for carbohydrates.
In order to interpret the corresponding NMR parameters, which correspond to a time-averaged or 'virtual' conformer, it is
necessary to simulate the experimental data using the averaged geometrical representation obtained with molecular modelling
methods. This structural information can be transformed into theoretical NMR data using empirical Karplus-type equations for
the scalar coupling constants and the appropriate formalism for the relaxation parameters. In the case of relaxation data,
the 'model-free' spectral densities have been widely used in order to account for the internal motions in sugars. Several
studies have been conducted with truncated model-free spectral densities based on the assumption that internal motion is very
fast with respect to overall tumbling.
In this report we present experimental and theoretical evidence that suggests that this approach is not justified. Indeed,
recent results show that even in the case of moderate-sized carbohydrates internal motions are occurring on the same timescale
as molecular reorientation. Simulations of relaxation parameters (NOESY volumes, proton cross-relaxation rates, carbon T1
and nOe values) in the dispersion range (0.1<Tc<5 ns) show that rates of internal motion can be fairly precisely defined with
respect to overall tumbling. Experimental data for a variety of oligosaccharides clearly indicate similar timescales for internal
and overall motion.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献