病毒衣壳结构亚单位的种类数与三角形剖分数关系的研究和探讨

本文报道了在正廿面体病毒衣壳中,当蛋白结构亚单位以“三聚体”的形式聚集在单位三角形(?)时,其亚单位的种类数应等于该病毒的三角形剖分数值。     

Targeting NADPH Oxidase and Phospholipases A2 in Alzheimer’s Disease

Alzheimer’s disease (AD) is marked by an increase in the production of extracellular beta amyloid plaques and intracellular neurofibrillary tangles associated with a decline in brain function. Increases in oxidative stress are regarded as an early sign of AD pathophysiology, although the source of reactive oxygen species (ROS) and the mechanism(s) whereby beta amyloid peptides (Aβ) impact oxidative stress have not been adequately investigated. Recent studies provide strong evidence for the involvement of NADPH oxidase and its downstream oxidative signaling pathways in the toxic effects elicited by Aβ. ROS produced by NADPH oxidase activate multiple signaling pathways leading to neuronal excitotoxicity and glial cell-mediated inflammation. This review describes recent studies demonstrating the neurotoxic effects of Aβ in conjunction with ROS produced by NADPH oxidase and the downstream pathways leading to activation of cytosolic phospholipase A₂ (PLA₂) and secretory PLA₂. In addition, this review also describes recent studies using botanical antioxidants to protect against oxidative damage associated with AD. Investigating the metabolic and signaling pathways involving Aβ NADPH oxidase and PLA₂ can help understand the mechanisms underlying the neurodegenerative effects of oxidative stress in AD. This information should provide new therapeutic approaches for prevention of this debilitating disease.     

Proteomic identification of the cerebral cavernous malformation signaling complex

Cerebral cavernous malformations (CCM) are sporadic or inherited vascular lesions of the central nervous system characterized by dilated, thin-walled, leaky vessels. Linkage studies have mapped autosomal dominant mutations to three loci: ccm1 (KRIT1), ccm2 (OSM), and ccm3 (PDCD10). All three proteins appear to be scaffolds or adaptor proteins, as no enzymatic function can be attributed to them. Our previous results demonstrated that OSM is a scaffold for the assembly of the GTPase Rac and the MAPK kinase kinase MEKK3, for the hyperosmotic stress-dependent activation of p38 MAPK. Herein, we show that the three CCM proteins are members of a larger signaling complex. To define this complex, epitope-tagged wild type OSM or OSM harboring the mutation of F217-->A, which renders the OSM phosphotyrosine binding (PTB) domain unable to bind KRIT1, were stably introduced into RAW264.7 mouse macrophages. FLAG-OSM or FLAG-OSMF217A and the associated complex members were purified by immunoprecipitation using anti-FLAG antibody. OSM binding partners were identified by gel-based methods combined with electrospray ionization-MS or by multidimensional protein identification technology (MudPIT). Previously identified proteins that associate with OSM including KRIT1, MEKK3, Rac, and the KRIT1-binding protein ICAP-1 were found in the immunoprecipitates. In addition, we show for the first time that PDCD10 binds to OSM and is found in cellular CCM complexes. Other prominent proteins that bound the CCM complex include EF1A1, RIN2, and tubulin, with each interaction disrupted with the OSMF217A mutant protein. We further show that PDCD10 binds phosphatidylinositol di- and triphosphates and OSM binds phosphatidylinositol monophosphates. The findings define the targeting of the CCM complex to membranes and to proteins regulating trafficking and the cytoskeleton.     

Achieving Molecular Selectivity in Imaging Using Multiphoton Raman Spectroscopy Techniques

In the case of most optical imaging methods, contrast is generated either by physical properties of the sample (Differential Image Contrast, Phase Contrast), or by fluorescent labels that are localized to a particular protein or organelle. Standard Raman and infrared methods for obtaining images are based upon the intrinsic vibrational properties of molecules, and thus obviate the need for attached fluorophores. Unfortunately, they have significant limitations for live-cell imaging. However, an active Raman method, called Coherent Anti-Stokes Raman Scattering (CARS), is well suited for microscopy, and provides a new means for imaging specific molecules. Vibrational imaging techniques, such as CARS, avoid problems associated with photobleaching and photo-induced toxicity often associated with the use of fluorescent labels with live cells. Because the laser configuration needed to implement CARS technology is similar to that used in other multiphoton microscopy methods, such as two-photon fluorescence and harmonic generation, it is possible to combine imaging modalities, thus generating simultaneous CARS and fluorescence images. A particularly powerful aspect of CARS microscopy is its ability to selectively image deuterated compounds, thus allowing the visualization of molecules, such as lipids, that are chemically indistinguishable from the native species.     

25-Hydroxyvitamin D depletion does not exacerbate MPTP-induced dopamine neuron damage in mice

Recent clinical evidence supports a link between 25-hydroxyvitamin D insufficiency (serum 25-hydroxyvitamin D [25(OH)D] levels <30 ng/mL) and Parkinson's disease. To investigate the effect of 25(OH)D depletion on neuronal susceptibility to toxic insult, we induced a state of 25(OH)D deficiency in mice and then challenged them with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We found there was no significant difference between control and 25(OH)D-deficient animals in striatal dopamine levels or dopamine transporter and tyrosine hydroxylase expression after lesioning with MPTP. Additionally, we found no difference in tyrosine hydroxylase expression in the substantia nigra pars compacta. Our data suggest that reducing 25(OH)D serum levels in mice has no effect on the vulnerability of nigral dopaminergic neurons in vivo in this model system of parkinsonism.     

Human histone gene organization : Identification of a histone gene polymorphism prevalent in a black population

Analysis of the restriction enzyme digests of total genomic DNAs from a broad spectrum of human cell lines and from individuals with different genetic backgrounds, by hybridization with a series of cloned human histone sequences, indicated restriction site polymorphisms (RSPs) for two adjacent human histone genes which reside on chromosome 1. In most cell lines and individuals examined we observed a single 2.05 kb H4 histone HindIII fragment and a 7.0 kb H3 histone HindIII fragment. In contrast, the polymorphisms were manifested as a 2.15 kb H4 HindIII fragment and a 9.1 kb H3 HindIII fragment. From population studies, we were able to show that there is no linkage disequilibrium between these two polymorphic restriction sites. Nor was there any apparent correlation between the presence of the H3/H4 histone polymorphisms and maintenance of the transformed karyotype, passage in culture, transformation or tumor progression. These chromosome 1 H3 and H4 histone gene polymorphisms are common in the American Black population and, in our survey of individuals, were not found in the American Caucasian population. Among the American Blacks studied, the frequency of the H3 HindIII(-) allele is 43% and of the H4 HindIII(-) allele 30%. In limited family studies, we were unable to detect recombination between these two physically linked alleles.     

Induction of Fas and Fas-ligand expression in plasmacytoma cells by a cytotoxic factor secreted by murine macrophages

Induction of tumoricidal activity is one of the major functions of activated macrophages. Our previous study demonstrated that P388D1 murine macrophage-like cells secreted a plasmacytoma cytotoxic factor (PCF) that selectively killed certain tumor cell lines including MOPC-315 plasmacytoma in vitro. Our subsequent studies demonstrated that PCF killed MOPC-315 cells by induction of apoptosis. In this report, the involvement of Fas and Fas ligand (FasL) in PCF-induced apoptosis was investigated. Results suggest that expression of Fas mRNA time-dependently increased in PCF-treated cells and reached an optimal level after 36 h of treatment. The augmented effect of PCF on Fas mRNA expression was significantly reduced by the addition of CB7.C2, an anti-PCF monoclonal antibody. The expression of FasL mRNA was also induced by PCF and reached an optimal level at 24 h, but sharply decreased after 36 h of treatment. Caspase-3 is one of the proteolytic enzymes that can be activated by the Fas-FasL interaction. In our studies, the enzymatic activity of caspase-3 was significantly induced by PCF after 6 h of treatment and reached an optimal level at 12 h. The augmented effect of PCF on caspase activity was significantly reduced by the addition of CB7.C2 and the caspase-3-specific inhibitor, DEVD-fmk. Therefore, PCF-treated plasmacytoma cells might undergo apoptosis via interaction between Fas and FasL.     

β-Amyloid-Induced Endothelial Necrosis and Inhibition of Nitric Oxide Production

Deposits of amyloid β-peptide (Aβ) in senile plaques and cerebral blood vessels is the prominent feature of Alzheimer's disease (AD), regardless of genetic predisposition. The cellular origin of cerebral deposits of Aβ or its precise role in the neurodegenerative process has not been established. Recently we demonstrated a novel action of β-amyloid on blood vessels—vasoactivity and endothelial damage through superoxide radicals. Since endothelial dysfunction is associated with vascular degenerative diseases, we examined the direct action of Aβ on endothelial cells in culture. Cells treated with Aβ displayed characteristics of necrotic cell death which was prevented by the free radical scavenging enzyme superoxide dismutase. Stimulation of endothelial nitric oxide (NO) production by the calcium ionophore, A23187, or bradykinin was inhibited by β-amyloid. We conclude that an imbalance of NO and oxygen radicals may mediate the Aβ-induced endothelial damage on endothelial cells in culture and may also contribute to a variety of pathophysiological conditions associated with aging: hypertension, cerebral ischemia, vasospasm, or stroke.