Identification of positions in the human neuropeptide Y/peptide YY receptor Y2 that contribute to pharmacological differences between receptor subtypes

The members of the neuropeptide Y (NPY) family are key players in food-intake regulation. In humans this family consists of NPY, peptide YY (PYY) and pancreatic polypeptide (PP) which interact with distinct preference for the four receptors showing very low sequence identity, i.e. Y1, Y2, Y4 and Y5. The binding of similar peptides to these divergent receptors makes them highly interesting for mutagenesis studies. We present here a site-directed mutagenesis study of four amino acid positions in the human Y2 receptor. T^3.40 was selected based on sequence alignments both between subtypes and between species and G^2.68, L^4.60 and Q^6.55 also on previous binding studies of the corresponding positions in the Y1 receptor. The mutated receptors were characterized pharmacologically with the peptide agonists NPY, PYY, PYY(3-36), NPY(13-36) and the non-peptide antagonist BIIE0246. Interestingly, the affinity of NPY and PYY(3-36) increased for the mutants T^3.40I and Q^6.55A. Increased affinity was also observed for PYY to Q^6.55A. PYY(3-36) displayed decreased affinity for G^2.68N and L^4.60A whereas binding of NPY(13-36) was unaffected by all mutations. The antagonist BIIE0246 showed decreased affinity for T^3.40I, L^4.60A and Q^6.55A. Although all positions investigated were found important for interaction with at least one of the tested ligands the corresponding positions in hY1 seem to be of greater importance for ligand binding. Furthermore these data indicate that binding of the agonists and the antagonist differs in their points of interaction. The increase in the binding affinity observed may reflect an indirect effect caused by a conformational change of the receptor. These findings will help to improve the structural models of the human NPY receptors.     

Engineered Polyallylamine Nanoparticles for Efficient In Vitro Transfection

Purpose Cationic polymers (i.e. polyallylamine, poly-L-lysine) having primary amino groups are poor transfection agents and possess high cytotoxicity index when used without any chemical modification and usually entail specific receptor mediated endocytosis or lysosomotropic agents to execute efficient gene delivery. In this report, primary amino groups of polyallylamine (PAA, 17 kDa) were substituted with imidazolyl functions, which are presumed to enhance endosomal release, and thus enhance its gene delivery efficiency and eliminate the requirement of external lysosomotropic agents. Further, systems were cross-linked with polyethylene glycol (PEG) to prepare PAA-IAA-PEG (PIP) nanoparticles and evaluated them in various model cell lines. Materials and Methods The efficacy of PIP nanoparticles in delivering a plasmid encoding enhanced green fluorescent protein (EGFP) gene was assessed in COS-1, N2a and HEK293 cell lines, while their cytotoxicity was investigated in COS-1 and HEK293 cell lines. The PAA was chemically modified using imidazolyl moieties and ionically cross-linked with PEG to engineer nanoparticles. The extent of substitution was determined by ninhydrin method. The PIP nanoparticles were further characterized by measuring the particle size (dynamic light scattering and transmission electron microscopy), surface charge (zeta potential), DNA accessibility and buffering capacity. The cytotoxicity was examined using the MTT method. Results In vitro transfection efficiency of synthesized nanoparticles is increased up to several folds compared to native polymer even in the presence of serum, while maintaining the cell viability over 100% in COS-1 cells. Nanoparticles possess positive zeta potential between 5.6–13 mV and size range of 185–230 nm in water. The accessibility experiment demonstrated that nanoparticles with higher degree of imidazolyl substitution formed relatively loose complexes with DNA. An acid-base titration showed enhanced buffering capacity of modified PAA. Conclusions The PIP nanoparticles reveal tremendous potential as novel delivery system for achieving improved transfection efficiency, while keeping the cells at ease.     

蚊期和红内期持续表达绿色荧光蛋白的重组约氏疟原虫

目的 构建蚊期、红内期持续表达绿色荧光蛋白（GFP）的约氏疟原虫BY265株。 方法 用SacⅡ酶酶切含有伯氏疟原虫ssu-rrna基因和GFP基因的重组质粒pl0017使之线性化,用电转化的方法将该重组质粒转化入红内期约氏疟原虫BY265株,获BY265-EGFP重组疟原虫,尾静脉注射感染昆明小鼠,24～30 h后用乙胺嘧啶饲喂小鼠5～6 d,鼠尾静脉采血涂片观察原虫感染率。以疟原虫基因组DNA为模板,PCR鉴定转染重组质粒pl0017的约氏疟原虫。斯氏按蚊叮咬感染BY265-EGFP重组疟原虫的小鼠,按蚊血餐后第7天和第16天解剖蚊胃和唾液腺,观察疟原虫能否在蚊体内正常发育。 结果 荧光显微镜观察到呈绿色荧光的红内期各期形态正常的约氏疟原虫。PCR检测结果表明,GFP和ssu-rrna基因已成功整合到约氏疟原虫基因组中。按蚊感染实验证实重组BY265株能在蚊体内正常发育。 结论 构建了蚊期、红内期持续表达绿色荧光蛋白的约氏疟原虫。     

A review of neurohormone GPCRs present in the fruitfly Drosophila melanogaster and the honey bee Apis mellifera

G protein-coupled receptor (GPCR) genes are large gene families in every animal, sometimes making up to 1-2% of the animal's genome. Of all insect GPCRs, the neurohormone (neuropeptide, protein hormone, biogenic amine) GPCRs are especially important, because they, together with their ligands, occupy a high hierarchic position in the physiology of insects and steer crucial processes such as development, reproduction, and behavior. In this paper, we give a review of our current knowledge on Drosophila melanogaster GPCRs and use this information to annotate the neurohormone GPCR genes present in the recently sequenced genome from the honey bee Apis mellifera. We found 35 neuropeptide receptor genes in the honey bee (44 in Drosophila) and two genes, coding for leucine-rich repeats-containing protein hormone GPCRs (4 in Drosophila). In addition, the honey bee has 19 biogenic amine receptor genes (21 in Drosophila). The larger numbers of neurohormone receptors in Drosophila are probably due to gene duplications that occurred during recent evolution of the fly. Our analyses also yielded the likely ligands for 40 of the 56 honey bee neurohormone GPCRs identified in this study. In addition, we made some interesting observations on neurohormone GPCR evolution and the evolution and co-evolution of their ligands. For neuropeptide and protein hormone GPCRs, there appears to be a general co-evolution between receptors and their ligands. This is in contrast to biogenic amine GPCRs, where evolutionarily unrelated GPCRs often bind to the same biogenic amine, suggesting frequent ligand exchanges ("ligand hops") during GPCR evolution.     

CD16+ monocytes exposed to HIV promote highly efficient viral replication upon differentiation into macrophages and interaction with T cells

The CD16+ subset of monocytes is dramatically expanded in peripheral blood during progression to AIDS, but its contribution to HIV pathogenesis is unknown. Here, we demonstrate that CD16+ but not CD16- monocytes promote high levels of HIV replication upon differentiation into macrophages and interaction with T cells. Conjugates formed between CD16+ monocyte-derived macrophages and T cells are major sites of viral replication. Furthermore, similar monocyte-T cell conjugates detected in peripheral blood of HIV-infected patients harbor HIV DNA. Thus, expansion of CD16+ monocytes during HIV infection and their subsequent recruitment into tissues such as lymph nodes, brain, and intestine may contribute to HIV dissemination and establishment of productive infection in T cells.     

Silk-elastinlike protein polymers for matrix-mediated cancer gene therapy

Silk-elastinlike protein polymers (SELPs) are recombinant polymers designed from silk fibroin and mammalian elastin amino acid repeats. These are versatile materials that have been examined as controlled release systems for intratumoral gene delivery. SELP hydrogels comprise monodisperse and tunable polymers that have the capability to control and localize the release and expression of plasmid DNA and viruses. This article reviews recent developments in the synthesis and characterization of SELP hydrogels and their use for matrix-mediated gene delivery.     

Mouse cortical inhibitory neuron type that coexpresses somatostatin and calretinin

Mammalian cortex contains a diversity of inhibitory neuron types, each with distinct morphological, immunochemical, and/or physiological properties. In rat cortex, chemical markers distinguish at least four distinct and nonoverlapping neuron classes based on expression of parvalbumin (PV), somatostatin (SST), calretinin (CR), and cholecystokinin (CCK). It has generally been assumed that these classifications should also apply to other rodent species. In mouse cortex, however, we found significant colocalization of SST and CR in inhibitory neurons; about 30% of SST-positive cells contained CR, and about 33% of CR-positive cells contained SST across frontal, somatosensory (S1), and visual cortex (V1). The SST and CR colocalized cells were concentrated in layer 2/3. We further characterized morphological and physiological properties of the mouse cortical inhibitory neuron types that express SST by using "GIN" transgenic mice, in which GFP is expressed in a subset of SST inhibitory neurons (see Oliva et al. [2000] J Neurosci 20:3354-3368). Generally, both SST/CR+ cells and SST/CR- cells exhibited morphological features of Martinotti cells as described in rat cortex, and they also had similar accommodating spike-firing patterns. However, they differed significantly in quantitative comparisons of morphology and spike shapes. SST/CR+ cells had more horizontally extended dendritic fields and more primary process than did SST/CR- cells; and SST/CR- cells had narrower action potential widths and faster afterhyperpolarization than did SST/CR+ cells. Thus, our data show an important species difference in the chemical distinction of inhibitory neuron subtypes, and indicate that colocalization of CR in SST cells correlates with different morphological and physiological features.