Altered agonist sensitivity of a mutant V2 receptor suggests a novel therapeutic strategy for nephrogenic diabetes insipidus.

Loss of function mutations of the type 2 vasopressin receptor (V2R) in kidney can lead to nephrogenic diabetes insipidus (NDI). We studied a previously described, but uncharacterized mutation of V2R (N321K missense mutation) of an NDI patient. The properties of the mutant receptor were evaluated. We constructed a highly sensitive Epac based BRET (bioluminescence resonance energy transfer) biosensor to perform real-time cAMP measurements after agonist stimulation of transiently transfected HEK293 cells with V2Rs. beta-arrestin binding of the activated receptors was examined with luciferase-tagged beta-arrestin and mVenus-tagged V2Rs using BRET technique. Cell surface expressions of HA-tagged receptors were determined with flow cytometry using anti-HA-Alexa488 antibodies. Cellular localization examinations were implemented with fluorescent tagged receptors visualized with confocal laser-scanning microscopy. The effect of various vasopressin analogues on V1R was tested on mouse arteries by wire myography. N321K mutant V2R showed normal cell surface expression but the potency of AVP for cAMP generation was low, while the clinically used desmopressin (dDAVP) was not efficient. The beta-arrestin binding and internalization properties of the mutant receptor were also different compared to the wild type. Function of the mutant receptor can be rescued with administration of V2R receptor agonist dVDAVP, which had no detectable side effects on V1R in the effective cAMP generating concentrations. Based on the findings we could propose a therapeutical strategy for NDI patients carrying the N321K mutation, since our in vivo experiments suggest that dVDAVP could rescue the function of the N321K-V2R without significant side effect on V1R

Correction: Improved methodical approach for quantitative BRET analysis of G protein coupled receptor dimerization

<p>Correction: Improved Methodical Approach for Quantitative BRET Analysis of G Protein Coupled Receptor Dimerization</p

Mutation in the V2 vasopressin receptor gene, AVPR2, causes nephrogenic syndrome of inappropriate diuresis

Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a recently discovered rare disease caused by gain-of-function mutations of the V2 vasopressin receptor gene, AVPR2. To date, mutations of Phe229 and Arg137 have been identified as gain-of-function in the V2 vasopressin receptor (V2R). These receptor mutations lead to hyponatremia, which may lead to clinical symptoms in infants. Here we present a newly identified I130N substitution in exon 2 of the V2R gene in a family, causing NSIAD. This I130N mutation resulted in constitutive activity of the V2R with constitutive cyclic adenosine monophosphate (cAMP) generation in HEK293 cells. This basal activity could be blocked by the inverse agonist tolvaptan and arginine-vasopressin stimulation enhanced the cAMP production of I130N-V2R. The mutation causes a biased receptor conformation as the basal cAMP generation activity of I130N does not lead to interaction with β-arrestin. The constitutive activity of the mutant receptor caused constitutive dynamin-dependent and β-arrestin-independent internalization. The inhibition of basal internalization using dominant-negative dynamin resulted in an increased cell surface expression. In contrast to the constitutive internalization, agonist-induced endocytosis was β-arrestin dependent. Thus, tolvaptan could be used for treatment of hyponatremia in patients with NSIAD who carry the I130N-V2R mutation.Kidney International advance online publication, 1 July 2015; doi:10.1038/ki.2015.181. © 2015 International Society of Nephrolog

What have we learned from two-pore potassium channels? Their molecular configuration and function in the human heart

Two-pore domain potassium channels (K2P) control excitability, stabilize the resting membrane potential below firing threshold, and accelerate repolarisation in different cells. Until now, fifteen different genes for the six K2P channel subfamily were cloned. The pore-forming part is translated from two genes and they are built up from a dimer of two two-unit transmembrane domains functioning with a wide spectrum of physiological profiles. K2P ion channels were discovered in the last two decades and gave novel opportunity to recognize the complex molecular mechanism of the potassium ion flux, and may lead to the design of individual drug targeting in the future. In this review, we summarise the structure, function, channelopathies and pharmacological silhouette of the two-pore potassium channels in the human tissues. In addition, we present the computer model of the partially reconstructed wild type K2P1/TWIK1 lacking the intracellular C and N terminal loop

Studia Litteraria

Baffy Dezső, Arany János: Epilógus, verselemzés, 5-14. Szuromi Lajos, Kettős ritmus Vajda János verseiben, 15-42. Barta János, Vajda János: Nádas tavon, verselemzés, 43-52. Erdélyi Ildikó, Mythologia, Egy Babits-novella elemzése, 53-64. Imre László, Sklovszkij prózaelmélete, A prózaelemzés történetéhez, 65-80. Fülöp László, Vázlat Csoóri Sándor lírájáról, 81-94. Kovács Sándor Iván - Kulcsár Péter, Dedikált disputációk Debrecenben, 95-102. Győrffy Miklós, Újabb kutatások Madách körül, 103-126

Pulmonary Tuberculosis due to Mycobacterium bovis in Captive Siberian Tiger

We report the first case of pulmonary tuberculosis caused by Mycobacterium bovis subsp. caprae in a captive Siberian tiger, an endangered feline. The pathogen was isolated from a tracheal aspirate obtained by bronchoscopy. This procedure provided a reliable in vivo diagnostic method in conjunction with conventional and molecular tests for the detection of mycobacteria