102,040 research outputs found
Minireview: aquaporin 2 trafficking
No full textIn the kidney aquaporin-2 (AQP2) provides a target for hormonal regulation of water transport by vasopressin. Shortterm control of water permeability occurs via vesicular trafficking of AQP2 and long-term control through changes in the abundance of AQP2 and AQP3 water channels. Defective AQP2 trafficking causes nephrogenic diabetes insipidus, a condition characterized by the kidney inability to produce concentrated urine because of the insensitivity of the distal nephron to vasopressin. AQP2 is redistributed to the apical membrane of collecting duct cells through activation of a cAMP signaling cascade initiated by the binding of vasopressin to its V2-receptor. Protein kinase A-mediated phosphorylation of AQP2 has been proposed to be essential in regulating AQP2-containing vesicle exocytosis. Cessation of the stimulus is followed by endocytosis of the AQP2 proteins exposed on the plasma membrane and their recycling to the original stores, in which they are retained. Soluble N-ethylmaleimide sensitive fusion factor attachment protein receptors ( SNARE) and actin cytoskeleton organization regulated by small GTPase of the Rho family were also proved to be essential for AQP2 trafficking. Data for functional involvement of the SNARE vesicle-associated membrane protein 2 in AQP2 targeting has recently been provided. Changes in AQP2 expression/trafficking are of particular importance in pathological conditions characterized by both dilutional and concentrating defects. One of these conditions, hypercalciuria, has shown to be associated with alteration of AQP2 urinary excretion. More precisely, recent data support the hypothesis that, in vivo external calcium, through activation of calcium-sensing receptors, modulates the expression/trafficking of AQP2. Together these findings underscore the importance of AQP2 in kidney pathophysiology
Na+-K+-2Cl- cotransporter type 2 trafficking and activity: The role of interacting proteins
No full textThe central role of Na+–K+–2Cl− cotransporter type 2 (NKCC2) in vectorial transepithelial salt reabsorption in
thick ascending limb cells from Henle’s loop in the kidney is evidenced by the effects of loop diuretics, the
pharmacological inhibitors of NKCC2, that are amongst the most powerful antihypertensive drugs available to
date. Moreover, genetic mutations of the NKCC2 encoding gene resulting in impaired apical targeting and function
of NKCC2 transporter give rise to a pathological phenotype known as type I Bartter syndrome, characterised by
a severe volume depletion, hypokalaemia and metabolic alkalosis with high prenatal mortality. On the contrary,
excessive NKCC2 activity has been linkedwith inherited hypertension in humans and in rodent models. Interestingly,
in animal models of hypertension, NKCC2 upregulation is achieved by post-translational mechanisms underlining
the need to analyse the molecular mechanisms involved in the regulation of NKCC2 trafficking and activity to gain insights in the pathogenesis of hypertension
Hypotonicity causes actin reorganization and recruitment of the actin-binding ERM protein moesin in membrane protrusions in collecting duct principal cells.
No full textContains fulltext :
52752.pdf (Publisher’s version ) (Closed access)Hypotonicity-induced cell swelling is characterized by a modification in cell architecture associated with actin cytoskeleton remodeling. The ezrin/radixin/moesin (ERM) family proteins are important signal transducers during actin reorganization regulated by the monomeric G proteins of the Rho family. We report here that in collecting duct CD8 cells hypotonicity-induced cell swelling resulted in deep actin reorganization, consisting of loss of stress fibers and formation of F-actin patches in membrane protrusions where the ERM protein moesin was recruited. Cell swelling increased the interaction between actin and moesin and induced the transition of moesin from an oligomeric to a monomeric functional conformation, characterized by both the COOH- and NH(2)-terminal domains being exposed. In this conformation, which is stabilized by phosphorylation of a conserved threonine in the COOH-terminal domain by PKC or Rho kinase, moesin can bind interacting proteins. Interestingly, hypotonic stress increased the amount of threonine-phosphorylated moesin, which was prevented by the PKC-alpha inhibitor Go-6976 (50 nM). In contrast, the Rho kinase inhibitor Y-27632 (1 microM) did not affect the hypotonicity-induced increase in phosphorylated moesin. The present data represent the first evidence that hypotonicity-induced actin remodeling is associated with phosphorylated moesin recruitment at the cell border and interaction with actin
Data on the influence of inorganic clays to improve mechanical and healing properties of antibacterial Gellan gum-Manuka honey hydrogels
No full textThis work contains original data supporting our research paper “Advances in cartilage repair: the influence of inorganic clays to improve mechanical and healing properties of antibacterial Gellan gum-Manuka honey hydrogels”, by Maria A. Bonifacio, Andrea Cochis, Stefania Cometa, Annachiara Scalzone, Piergiorgio Gentile, Giuseppe Procino, Serena Milano, Alessandro C. Scalia, Lia Rimondini, Elvira De Giglio [1]. The main paper describes how four different clays (i.e., mesoporous silica, bentonite and halloysite nanotubes, coded as MS, BE and HNT) as cheap, abundant and versatile feed materials can be used for the preparation of highly performant hydrogels as cartilage substitutes, based on Gellan Gum (GG) and Manuka Honey (MH). Here the composites were further examined by means of Thermogravimetric Analysis (TGA), histological analysis (Alcian blue and Safranin-O) and static compression tests. This set of data strengthens the evidence that these hydrogels possess biological and physicochemical characteristics suitable for their application as reinforcing inorganic fillers in composite materials designed for cartilage regeneration
Histamine-induced AQP4 internalization in gastric cells is paralleled to an increase in AQP4 phosphorylation
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A heterotrimeric G protein of the Gi family is required for cAMP-triggered trafficking of aquaporin 2 in kidney epithelial cells.
No full textVasopressin is the key regulator of water homeostasis in vertebrates. Central to its antidiuretic action in mammals is the redistribution of the water channel aquaporin 2 (AQP2) from intracellular vesicles to the apical membrane of kidney epithelial cells, an event initiated by an increase in cAMP and activation of protein kinase A. The subsequent steps of the signaling cascade are not known. To identify proteins involved in the AQP2 shuttle we exploited a recently developed cell line (CD8) derived from the rabbit cortical collecting duct and stably transfected with rat AQP2 cDNA, Treatment of CD8 cells with pertussis toxin (PTX) inhibited both the vasopressin-induced increase in water permeability and the redistribution of AQP2 from an intracellular compartment to the apical membrane. ADP-ribosylation studies revealed the presence of at least two major PTX substrates, Correspondingly, two a: subunits of PTX-sensitive G proteins, G alpha(i2), and G alpha(i3), were identified by Western blotting. Introduction of a synthetic peptide corresponding to the C terminus of the G(i3) alpha subunit into permeabilized CD8 cells efficiently inhibited the cAMP-induced AQP2 translocation; a peptide corresponding to the a subunits of G(i1/2) was much less potent. Thus a member of the G(i) family, most likely G(i3), is involved in the cAMP-triggered targeting of AQP2-bearing vesicles to the apical membrane of kidney epithelial cells
Environmental Wind Tunnel Study on a Municipal Waste Incinerator
No full textIn this paper results concerning a diffusion experiment on a small scale model of a waste incinerator, carried out in a boundary layer wind tunnel, will be presented. At the beginning a description of the measurement system that has recently been placed in the wind tunnel will be given together with a study of repeatability of the measurements results. A comprehensive study of the flow mean characteristics at different position in the tunnel working section will be reported and at the end some vertical and horizontal concentration profiles results will be described and discussed
Aerodynamic behaviour of hyperbolic paraboloid shaped roofs: Wind tunnel tests, proper orthogonal decomposition and computational fluid dynamics analysis
No full textThe need to cover large areas while maintaining unobstructed interior spaces is a permanent challenge in the design of medium and large span roofs. In line with international trends, a technology already used in the past for this type of application, i.e. tensile structures made with nets of tension cables, is proposed anew. These structures meet the requirements of today's market in terms of lightness, innovation of materials, cost-effectiveness and lack of intermediate supports. However, tension structures are used rarely in Italy, also due to the lack of clear regulations on the structural design and the determination of environmental stresses on complex shapes such as hyperbolic paraboloids. This research follows two consecutive steps: the first is aimed at developing an optimized procedure of preliminary designs for the cable structure; the second is focused on the study of wind action on these structures. The shape selected for a parameterization leading to an optimized design of this kind of structures is the hyperbolic paraboloid. © Civil-Comp Press, 2009
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