蛋白酶活化受体-2的研究进展

蛋白酶活化受体(protease-activated receptors,PARs)属于G蛋白偶联受体家族成员,其N-末端被蛋白酶裂解后,可形成新的N-末端。新N-末端能够结合、激活自身受体。PAR-2是PARs的成员之一,其激活、灭活、脱敏、复敏、及其与信号转导途径的关系,尤其是与疾病(如呼吸道慢性炎症)的关系正倍受关注。     

Insight into the stability of the hydrophobic binding proteins of Escherichia coli: assessing the proteins for use as biosensors

Spectroscopic methods were used to monitor the unfolding of the leucine specific (LS) and the leucine-isoleucine-valine (LIV) binding proteins. Our studies indicate that ligand-free protein undergoes a simple two-state unfolding, whereas the protein-ligand complex undergoes a three-state unfolding model. Ligand binding causes significant stabilization of both proteins. There is correlation between ligand hydrophobicity and protein stabilization: the most hydrophobic ligand, isoleucine, causes the most significant stabilization of LIV protein. A disulfide bond present in N-domain of both proteins makes a large contribution to the protein stability of these periplasmic binding receptors.     

Citrus Leprosis and its Status in Florida and Texas: Past and Present

According to published reports from 1906 to 1968, leprosis nearly destroyed the Florida citrus industry prior to 1925. This was supported with photographs showing typical leprosis symptoms on citrus leaves, fruit, and twigs. Support for the past occurrence of citrus leprosis in Florida includes: (1) presence of twig lesions in affected orange blocks in addition to lesions on fruits and leaves and corresponding absence of similar lesions on grapefruit; (2) yield reduction and die-back on infected trees; and (3) spread of the disease between 1906 and 1925. Transmission electron microscopy (TEM) examination of tissue samples from leprosis-like injuries to orange and grapefruit leaves from Florida in 1997, and fruits from grapefruit and sweet orange varieties from Texas in 1999 and 2000 did not contain leprosis-like viral particles or viroplasm inclusions. In contrast, leprosis viroplasm inclusions were readily identified by TEM within green non-senescent tissues surrounding leprosis lesions in two of every three orange leaf samples and half of the fruit samples obtained from Piracicaba, Brazil. Symptoms of leprosis were not seen in any of the 24,555 orange trees examined across Florida during 2001 and 2002. The authors conclude that citrus leprosis no longer exists in Florida nor occurs in Texas citrus based on: (1) lack of leprosis symptoms on leaves, fruit, and twigs of sweet orange citrus varieties surveyed in Florida: (2) failure to find virus particles or viroplasm inclusion bodies in suspect samples from both Florida and Texas examined by TEM; (3) absence of documented reports by others on the presence of characteristic leprosis symptoms in Florida; (4) lack of its documented occurrence in dooryard trees or abandoned or minimal pesticide citrus orchard sites in Florida. In view of the serious threat to citrus in the U.S., every effort must be taken to quarantine the importation of both citrus and woody ornamental plants that serve as hosts for Brevipalpus phoenicis (Geijskes), B. californicus (Banks), and B. obovatus Donnadieu (Acari: Tenuipalpidae) from countries where citrus leprosis occurs.     

Impaired angiogenesis in neuropeptide Y (NPY)-Y2 receptor knockout mice

Which of Y1-Y5 receptors (Rs) mediate NPY's angiogenic activity was studied using Y2R-null mice and R-specific antagonists. In Y2R-null mice, NPY-induced aortic sprouting and in vivo Matrigel capillary formation were decreased by 50%; Y1R-antagonist blocked the remaining response. NPY-induced sprouting was equally inhibited by Y2R- (and Y5R- but less by Y1R-) antagonists in wild type mice. Spontaneous and NPY-induced revascularization of ischemic gastrocnemius muscles were similarly reduced in Y2R-null mice. Thus, NPY-induced angiogenesis, spontaneous and ischemic, is primarily mediated by Y2Rs. However, Y5Rs and, to a lesser degree Y1Rs, also may play a role in NPY-mediated angiogenesis.     

Novel roles for the flagellum in cell morphogenesis and cytokinesis of trypanosomes

Flagella and cilia are elaborate cytoskeletal structures conserved from protists to mammals, where they fulfil functions related to motility or sensitivity. Here we demonstrate novel roles for the flagellum in the control of cell size, shape, polarity and division of the protozoan Trypanosoma brucei. To investigate the function of the flagellum, its formation was perturbed by inducible RNA interference silencing of com ponents required for intraflagellar transport, a dynamic process necessary for flagellum assembly. First, we show that down-regulation of intraflagellar transport leads to assembly of a shorter flagellum. Strikingly, cells with a shorter flagellum are smaller, with a direct correlation between flagellum length and cell size. Detailed morphogenetic analysis reveals that the tip of the new flagellum defines the point where cytokinesis is initiated. Secondly, when new flagellum formation is completely blocked, non-flagellated cells are very short, lose their normal shape and polarity, and fail to undergo cytokinesis. We show that flagellum elongation controls formation of cytoskeletal structures (present in the cell body) that act as molecular organizers of the cell.     

Calmodulin-peptide interactions: apocalmodulin binding to the myosin light chain kinase target-site

Noncovalent binding of the synthetic peptide RS20 to calmodulin in the presence of calcium was confirmed by electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry to form a complex with a 1:1:4 calmodulin/RS20/calcium stoichiometry. There was no evidence for formation of a calmodulin-RS20-Ca(2) species. The absence of calmodulin-RS20-Ca(2) would be consistent with models in which the two globular domains are coupled functionally. There was evidence that calmodulin, RS20-calmodulin without associated calcium, and calmodulin-RS20-Ca(4) existed together in solution, whereas calmodulin-calcium complexes were absent. It is proposed that calcium binding to form the calmodulin-RS20-Ca(4) complex occurs after an initial RS20-calmodulin binding event, and serves to secure the target within the calmodulin structure. The binding of more than one RS20 molecule to calmodulin was observed to induce unfolding of calmodulin.     

Spectral karyotyping of mouse cell line WMP2

We have evaluated the mouse cell line WMP2 using both GTG-banding analysis and spectral karyotyping to verify the reliability of using this established cell line derived from WMP/WMP mice. The WMP cell lines contain easily identifiable metacentric fusion chromosomes and are used extensively for gene mapping. Because of karyotypical changes in the WMP1 cell line, WMP2 was examined. Our results demonstrate that WMP2 is stable during culture, and the karyotype is simple and easy to use. Based on the findings discussed in this paper, we recommend the use of the WMP2 cell line for future prospective gene mapping in the mouse.     

Effects of Ellagic Acid by Oral Administration on N-Acetylation and Metabolism of 2-Aminofluorene in Rat Brain Tissues

Numerous studies have demonstrated that the Acetyl Coenzyme A-dependent arylamine NAT enzyme exist in many tissues of experimental animals including humans, and that NAT has been shown to be exist in mouse brain tissue. Increased NAT activity levels are associated with increased sensitivity to the mutagenic effects of arylamine carcinogens. Attenuation of liver NAT activity is related to breast and bladder cancer processes. Therefore, the effects of ellagic acid (EA) on the in vitro and in vivo N-acetylation of 2-aminofluorene (AF) were investigated in cerebrum, cerebellum and pineal gland tissues from male Sprague-Dawley rats. For in vitro examination, cytosols with or without EA (0.5–500 M) co-treatment decreased 7–72%, 15–63% and 10–78% of AF acetylation for cerebrum, cerebellum and pineal gland tissues, respectively. For in vivo examination, EA and AF at the same time treated groups with all 3 examined tissues did show significant differences (the changes of total amounts of AF and AF metabolites based on the Anova analysis) when compared to the ones without EA cotreatment rats. The pretreatment of male rats with EA (10 mg/kg) 24 hr prior to the administration of AF (50 mg/kg) (one day of EA administration suffice to induce large changes in phase II enzyme activity) resulted in a 76% decrease in total AF and metabolites in pineal gland but did not show significant differences in cerebrum and cerebellum tissues. This is the first demonstration to show that EA decreases the N-acetylation of carcinogens in rat brain tissues.