Immunoexpression of aquaporins 1, 2, 3 and 4 in kidney of yak (Bos grunniens) on the Qinghai-Tibetan Plateau

Aquaporins (AQP) 1, 2, 3 and 4 belong to the aquaporin water channel family and play an important role in urine concentration by reabsorption of water from renal tubule fluid. Renal AQPs have not been reported in the yak (Bos grunniens), which resides in the Qinghai Tibetan Plateau. We investigated AQPs 1?4 expressions in the kidneys of Yak using immunohistochemical staining. AQP1 was expressed mainly in the basolateral and apical membranes of the proximal tubules and descending thin limb of the loop of Henle. AQP2 was detected in the apical plasma membranes of collecting ducts and distal convoluted tubules. AQP3 was located in the proximal tubule, distal tubule and collecting ducts. AQP4 was located in the collecting ducts, distal straight tubule, glomerular capillaries and peritubular capillaries. The expression pattern of AQPs 1?4 in kidney of yak was different from other species, which possibly is related to kidney function in a high altitude environment.     

Expression of human alpha-l-fucosyltransferase gene homologs in monkey kidney COS cells and modification of potential fucosyltransferase acceptor substrates by an endogenous glycosidase

Previous investigations on the monkey kidney COS cell line demonstrated the weak expression of fucosylated cell surface antigens and presence of endogenous fucosyltransferase activities in cell extracts. RT-PCR analyses have now revealed expression of five homologs of human fucosyltransferase genes, FUT1, FUT4, FUT5, FUT7, and FUT8, in COS cell mRNA. The enzyme in COS cell extracts acting on unsialylated Type 2 structures is closely similar in its properties to the alpha1,3- fucosyltransferase encoded by human FUT4 gene and does not resemble the product of the FUT5 gene. Although FUT1 is expressed in the COS cell mRNA, it has not been possible to demonstrate alpha1,2- fucosyltransferase activity in cell extracts but the presence of Le(y) and blood-group A antigenic determinants on the cell surface imply the formation of H-precursor structures at some stage. The most strongly expressed fucosyltransferase in the COS cells is the alpha1,6-enzyme transferring fucose to the innermost N -acetylglucosamine unit in N - glycan chains; this enzyme is similar in its properties to the product of the human FUT8 gene. The enzymes resembling the human FUT4 and FUT8 gene products both had pH optima of 7.0 and were resistant to 10 mM NEM. The incorporation of fucose into asialo-fetuin was optimal at 5.5 and was inhibited by 10 mM NEM. This result initially suggested the presence of a third fucosyltransferase expressed in the COS cells but we have now shown that triantennary N- glycans with terminal nonreducing galactose units, similar to those present in asialo-fetuin, are modified by a weak endogenous beta-galactosidase in the COS cell extracts and thereby rendered suitable substrates for the alpha1,6- fucosyltransferase.      

Quantitative Proteomics: Comparison of the Macular Bruch Membrane/Choroid Complex from Age-related Macular Degeneration and Normal Eyes

A quantitative proteomics analysis of the macular Bruch membrane/choroid complex was pursued for insights into the molecular mechanisms of age-related macular degeneration (AMD). Protein in trephine samples from the macular region of 10 early/mid-stage dry AMD, six advanced dry AMD, eight wet AMD, and 25 normal control post-mortem eyes was analyzed by LC MS/MS iTRAQ (isobaric tags for relative and absolute quantitation) technology. A total of 901 proteins was quantified, including 556 proteins from ≥3 AMD samples. Most proteins differed little in amount between AMD and control samples and therefore reflect the proteome of normal macular tissues of average age 81. A total of 56 proteins were found to be elevated and 43 were found to be reduced in AMD tissues relative to controls. Analysis by category of disease progression revealed up to 16 proteins elevated or decreased in each category. About 60% of the elevated proteins are involved in immune response and host defense, including many complement proteins and damage-associated molecular pattern proteins such as α-defensins 1–3, protein S100s, crystallins, histones, and galectin-3. Four retinoid processing proteins were elevated only in early/mid-stage AMD, supporting a role for retinoids in AMD initiation. Proteins uniquely decreased in early/mid-stage AMD implicate hematologic malfunctions and weakened extracellular matrix integrity and cellular interactions. Galectin-3, a receptor for advanced glycation end products, was the most significantly elevated protein in advanced dry AMD, supporting a role for advanced glycation end products in dry AMD progression. The results endorse inflammatory processes in both early and advanced AMD pathology, implicate different pathways of progression to advanced dry and wet AMD, and provide a new database for hypothesis-driven and discovery-based studies of AMD.Age-related macular degeneration (AMD)¹ is a leading cause of blindness worldwide (1, 2) and is approaching epidemic proportions in the United States (3). AMD is a progressive disease involving multiple genetic and environmental factors. Deposition of debris (termed “drusen”) along Bruch membrane in the macula is the first evidence of early AMD. Advanced AMD occurs in two forms, geographic atrophy and choroidal neovascularization (CNV). Geographic atrophy (advanced dry AMD) develops slowly and results in blindness when focal areas of the retinal pigment epithelium (RPE) degenerate in the macula. CNV (wet AMD) is characterized by the growth of new blood vessels from the choroid through Bruch membrane and the RPE. When these vessels hemorrhage, a blood clot accumulates between the RPE and the macular photoreceptors causing immediate central vision loss. CNV accounts for over 80% of debilitating visual loss in AMD, yet only 10–15% of AMD cases progress to wet AMD.There is growing evidence that AMD is in part an age-related inflammatory disease involving complement dysregulation, including AMD susceptibility genes encoding complement factors and the presence of complement proteins in drusen (1, 2, 4). An assortment of potential inducers of AMD have been proposed; however, the causes of the disease remain poorly defined. For example, many carrying AMD risk genotypes may never develop the disease (5), and only a fraction of those diagnosed with early AMD progress to advanced disease (6). We have proposed that oxidative protein modifications are among the catalysts of AMD (7), and a host of elevated oxidative modifications have been reported in AMD Bruch membrane, drusen, retina, RPE, and plasma (7–14). Two of these modifications, namely carboxymethyllysine and carboxyethylpyrrole (CEP), stimulate neovascularization in vivo (15, 16), and immunization with CEP-adducted protein has been shown to induce a dry AMD-like phenotype in mice (17). Yet many other factors have been reported to contribute to this complex disease, including for example cigarette smoking (18), cumulative light exposure (19), lipofuscin/retinoid toxicity (20), advanced glycation end products (8–10), and microbial infection (21).Toward a better understanding of the molecular pathways contributing to AMD pathology, we pursued quantitative proteomics analysis of the macular region of the Bruch membrane/choroid complex. Bruch membrane (see Fig. 1) is a stratified extracellular matrix (ECM) comprising a central elastin zone flanked by inner and outer collagenous layers and the basement membranes of the RPE and choriocapillaris (22). It serves as a semipermeable support for the RPE, which forms an integral part of the blood-retinal barrier and provides many vital functions for vision, including the rod retinoid visual cycle and phagocytosis of spent photoreceptors with export of degradation products to the blood. The Bruch membrane molecular sieve is thought to help regulate the diffusion of nutrients and waste products between the RPE and the bloodstream as well as to restrict cell migration (23). Age-related changes at this critical interface, including thickening and decreased permeability, have long been thought to disrupt normal retinal physiology and contribute to AMD (22, 23). We used LC MS/MS iTRAQ technology to quantify proteins from a relatively large number of age- and gender-matched AMD and normal macular tissues and to correlate proteomic changes with AMD progression. The results endorse inflammatory processes in AMD pathology, reveal molecular details previously unassociated with AMD, and provide a quantitative proteomics database from the critically important macular interface.Open in a separate windowFig. 1.Macular Bruch membrane tissue samples. Bruch membrane is a permeable extracellular matrix separating the RPE from the blood-bearing choroid as illustrated in a cross-section of the human eye (A) and a cross-section through the macular region (B). Photographs are shown of isolated Bruch membrane tissue before (C) and after (D) removal of 4-mm trephined tissue buttons for proteomics analysis (F, fovea) scale bar = 2.4 mm. A and B are reproduced with copyright permission from the Cleveland Clinic. Illustration by David Schumick. All rights reserved.     

Predicting functional upstream open reading frames in Saccharomyces cerevisiae

Background  

Some upstream open reading frames (uORFs) regulate gene expression (i.e., they are functional) and can play key roles in keeping organisms healthy. However, how uORFs are involved in gene regulation is not yet fully understood. In order to get a complete view of how uORFs are involved in gene regulation, it is expected that a large number of experimentally verified functional uORFs are needed. Unfortunately, wet-experiments to verify that uORFs are functional are expensive.     

Liver-Derived Systemic Factors Drive β Cell Hyperplasia in Insulin-Resistant States

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Highlights? Circulating nonneuronal factors drive β cell replication in LIRKO mice ? LIRKO serum increases mouse and human islet β cell replication in vitro ? LIRKO serum induces selective β cell replication in vivo ? Hepatocyte-derived factors stimulate mouse and human β cell replication in vitro