Protein conformational changes of Agrobacterium phytochrome Agp1 during chromophore assembly and photoconversion

Phytochromes are widely distributed photochromic biliprotein photoreceptors. Typical bacterial phytochromes such as Agrobacterium Agp1 have a C-terminal histidine kinase module; the N-terminal chromophore module induces conformational changes in the protein that lead to modulation of kinase activity. We show by protein cross-linking that the C-terminal histidine kinase module of Agp1 mediates stable dimerization. The fragment Agp1-M15, which comprises the chromophore module but lacks the histidine kinase module, can also form dimers. In this fragment, dimer formation was stronger for the far-red-absorbing form Pfr than for the red-absorbing form Pr. The same or similar behavior was found for Agp1-M15Delta9N and Agp1-M15Delta18N, which lack 9 and 18 amino acids of the N-terminus, respectively. The fragment Agp1-M20, which is derived from Agp1-M15 by truncation of the C-terminal "PHY domain" (191 amino acids), can also form dimers, but dimerization is independent of irradiation conditions. The cross-linking data also showed that the PHY domain is in tight contact with Lys 16 of the protein and that the nine N-terminal amino acids mediate oligomer formation. Limited proteolysis shows that the hinge region between the chromophore module and the histidine kinase and a part of the PHY domain become exposed upon Pr to Pfr photoconversion.     

Cdk5 is involved in NFT-like tauopathy induced by transient cerebral ischemia in female rats

Although neurofibrillary tangle (NFT) formation is a central event in both familial and sporadic Alzheimer's disease (AD), neither cellular origin nor functional consequence of the NFTs are fully understood. This largely is due to the lack of available in vivo models for neurofibrillary degeneration (NFD). NFTs have only been identified in transgenic mice, bearing a transgene for a rare hereditary neurodegenerative disease, frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP17). Epidemiological evidence suggests a much higher occurrence of dementia in stroke patients. This may represent the underlying cause of the pathogenesis of sporadic AD, which accounts for the majority of AD cases. We examined pathological markers of AD in a rodent stroke model. Here we show that after transient cerebral ischemia, hyperphosphorylated tau accumulates in neurons of the cerebral cortex in the ischemic area, forms filaments similar to those present in human neurodegenerative tauopathies and colocalizes with markers of apoptosis. As a potential underlying mechanism, we were able to determine that transient ischemia induced tau hyperphosphorylation and NFT-like conformations are associated with aberrant activation of cyclin dependent kinase 5 (Cdk5) and can be rescued by delivery of a potent, but non-specific cyclin dependent kinase inhibitor, roscovitine to the brain. Our study further indicates that accumulation of p35 and its calpain-mediated cleavage product, p25 may account for the deregulation of Cdk5 induced by transient ischemia. We conclude that Cdk5 may be the principal protein kinase responsible for tau hyperphosphorylation and may be a hallmark of the tauopathies in this stroke model.     

A20 attenuates vascular smooth muscle cell proliferation and migration through blocking PI3k/Akt singling <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis>

Summary A20 was originally characterized as a TNF-inducible gene in human umbilical vein endothelial cells. It is also induced in many other cell types by a wide range of stimuli. Expression of A20 has been shown to protect from TNF-induced apoptosis and also functions via a negative-feedback loop to block NF-kappaB activation induced by TNF and other stimuli. However, there are no reports on whether A20 can inhibit vascular smooth muscle cell proliferation in␣vivo. Here, we examined the effects of A20 on neointimal formation after balloon injury and TNF-α-induced vascular smooth muscle cells (VSMCs) proliferation and migration, as well as related molecular mechanisms in vitro and in vivo. We introduced adenovirus expressing A20 or GFP into rat carotid arterial segments after balloon injury. The effects of A20 were evaluated 14 days after gene delivery with morphometry and immunohistochemical staining for proliferating and apoptotic cells. Ad-A20 infection resulted in a significantly lower intima to media ratio and a greater lumen area compared with Ad-GFP infected group. Proliferation index was significantly reduced 14 days in Ad-A20 infection group. However, apoptotic index and caspase-3 activity were not significantly different between any groups at 14 days. In vitro experiments were performed to show that A20 markedly inhibited TNF-α-induced proliferation and migration in VSMCs. Further studies showed that A20 expression blocked artery injury- and TNF-α-activated PI3K/Akt/GSK3β/CREB pathway in vivo and in vitro. In conclusion, A20 attenuates neointimal formation after arterial injury as well as cell proliferation and migration in response to TNF-α in VSMCs through blocking PI3K/Akt/GSKβ-dependent activation of CREB. Ai-Bing Wang and Hong-Liang Li – contributed equally to this work. Contract grant sponsor: “973” Basic Research Form of China Contract Grant Number: 2006CB503801 and 2005CB522507     

Investigation on Microecology of Hair Root Fungi in Androgenetic Alopecia Patients

Mycopathologia - This study focused on the differences in hairy root fungal microecology between androgenetic alopecia patients and healthy individuals. Light microscopy was used to observe the...     

An immunosuppressive peptide from the horsefly inhibits inflammation by repressing macrophage maturation and phagocytosis

Ectoparasites repress host immune responses while they obtain nutrition from their hosts. Understanding the immunosuppressive mechanisms between ectoparasites and their hosts will provide new strategies to develop potential immunosuppressive drugs against immune disorder diseases. Previously, we have discovered that a small peptide, immunoregulin HA, from the horsefly (Hybomitra atriperoides) may play an immunosuppressive role in rat splenocytes. However, the targeting cells and detailed mechanisms of immunoregulin HA in immunosuppressive reactions are not well defined. Here, we show that immunoregulin HA reduces the secretion of proinflammatory cytokines upon lipopolysaccharide (LPS) stimulation. Interestingly, we discover that the major cytokines repressed by immunoregulin HA are secreted by macrophages, rather than by T cells. Furthermore, immunoregulin HA inhibits macrophage maturation and phagocytosis. Mechanically, the activations of c-JUN N-terminal kinase and extracellular signal-regulated kinase upon LPS stimulation are decreased by immunoregulin HA. Consistently, immunoregulin HA treatment exhibits an anti-inflammatory activity in a mouse model of adjuvant-induced paw inflammation. Taken together, our data reveal that immunoregulin HA conducts the anti-inflammatory activity by blocking macrophage functions.     

Characterizing differences in microbial community composition and function between Fusarium wilt diseased and healthy soils under watermelon cultivation

Plant and Soil - Continuous cropping of watermelon is known to result in the disruption of the rhizospheric bacteria and fungi that contribute to the occurrence of Fusarium wilt disease. However,...     

伪狂犬病毒跨突触示踪视觉系统神经网络的研究进展

伪狂犬病毒（PRV）作为一种亲神经性的病毒,它以其自我复制、跨突触、特异性传递的三大优势在揭示神经系统中功能性神经元之间的连接发挥着重大的作用。经基因重组后的伪狂犬病毒不但继承了原有病毒的优势,同时还延伸出其他特异性的功能,如重组后加入了荧光蛋白的伪狂犬病毒在视觉系统神经通路的研究中发挥了重要作用。本文就目前伪狂犬病毒跨突触示踪视觉系统神经网络中的研究做一综述。