Description: Short QT3 syndrome (SQT3S) is a cardiac disorder characterized by a high risk of mortality and associated with mutations in Kir2.1 ( KCNJ2 ) channels. The molecular mechanisms leading to channel dysfunction, cardiac rhythm disturbances and neurodevelopmental disorders, potentially associated with SQT3S, remain incompletely understood. Here, we report on monozygotic twins displaying a short QT interval on electrocardiogram recordings and autism–epilepsy phenotype. Genetic screening identified a novel KCNJ2 variant in Kir2.1 that (i) enhanced the channel's surface expression and stability at the plasma membrane, (ii) reduced protein ubiquitylation and degradation, (iii) altered protein compartmentalization in lipid rafts by targeting more channels to cholesterol-poor domains and (iv) reduced interactions with caveolin 2. Importantly, our study reveals novel physiological mechanisms concerning wild-type Kir2.1 channel processing by the cell, such as binding to both caveolin 1 and 2, protein degradation through the ubiquitin–proteasome pathway; in addition, it uncovers a potential multifunctional site that controls Kir2.1 surface expression, protein half-life and partitioning to lipid rafts. The reported mechanisms emerge as crucial also for proper astrocyte function, suggesting the need for a neuropsychiatric evaluation in patients with SQT3S and offering new opportunities for disease management.

Description: Using a cell-free bioluminescence resonance energy transfer strategy we compared the levels of spontaneous and ligand-induced receptor-G protein coupling in δ (DOP) and μ (MOP) opioid receptors. In this assay GDP can suppress spontaneous coupling, thus allowing its quantification. The level of constitutive activity was 4–5 times greater at the DOP than at the MOP receptor. A series of opioid analogues with a common peptidomimetic scaffold displayed remarkable inversions of efficacy in the two receptors. Agonists that enhanced coupling above the low intrinsic level of the MOP receptor were inverse agonists in reducing the greater level of constitutive coupling of the DOP receptor. Yet the intrinsic activities of such ligands are identical when scaled over the GDP base line of both receptors. This pattern is in conflict with the predictions of the ternary complex model and the “two state” extensions. According to this theory, the order of spontaneous and ligand-induced coupling cannot be reversed if a shift of the equilibrium between active and inactive forms raises constitutive activation in one receptor type. We propose that constitutive activation results from a lessened intrinsic barrier that restrains spontaneous coupling. Any ligand, regardless of its efficacy, must enhance this constraint to stabilize the ligand-bound complexed form.

Description: Megalencephalic leukoencephalopathy with subcortical cysts (MLC), a rare leukodystrophy characterized by macrocephaly, subcortical fluid cysts and myelin vacuolation, has been linked to mutations in the MLC1 gene. This gene encodes a membrane protein that is highly expressed in astrocytes. Based on MLC pathological features, it was proposed that astrocyte-mediated defects in ion and fluid homeostasis could account for the alterations observed in MLC-affected brains. However, the role of MLC1 and the effects of pathological mutations on astrocyte osmoregulatory functions have still to be demonstrated. Using human astrocytoma cells stably overexpressing wild-type MLC1 or three known MLC-associated pathological mutations, we investigated MLC1 involvement in astrocyte reaction to osmotic changes using biochemical, dynamic video imaging and immunofluorescence techniques. We have found that MLC1 overexpressed in astrocytoma cells is mainly localized in the plasma membrane, is part of the Na,K-ATPase-associated molecular complex that includes the potassium channel Kir4.1, syntrophin and aquaporin-4 and functionally interacts with the calcium permeable channel TRPV4 (transient receptor potential vanilloid-4 cation channel) which mediates swelling-induced cytosolic calcium increase and volume recovery in response to hyposmosis. Pathological MLC mutations cause changes in MLC1 expression and intracellular localization as well as in the astrocyte response to osmotic changes by altering MLC1 molecular interactions with the Na,K-ATPase molecular complex and abolishing the increase in calcium influx induced by hyposmosis and treatment with the TRPV4 agonist 4αPDD. These data demonstrate, for the first time, that MLC1 plays a role in astrocyte osmo-homeostasis and that defects in intracellular calcium dynamics may contribute to MLC pathogenesis.

Description: The increasing overexploitation of water resources is observed on a global scale in the previous decades; this trend involves the coastal regions of Mediterranean Basin (Van Beynen et alii, 2012). As an effect of increasing groundwater discharge from coastal aquifers, the phenomenon of seawater intrusion is becoming a serious problem for most of the coastal aquifers, especially in the Mediterranean area (COST, 2003; COST, 2005). The aim of this paper is to present the modeling of a coastal porous aquifer located in the complex plain of Sibari (Southern Italy), a plain deeply modified as an effect of reclamation works realized after thirties. The model was implemented using piezometric historical data (from thirties) to establish the effect of seawater intrusion when the well discharge was negligible (natural conditions), the modification in subsequent decades, to be used for forecasting purpose and for evaluate the evolution of groundwater resource. The area actually represents a landscape with anthropic equilibrium based on the works of a land reclamation project (1960s-1990s). Study area is about 365 km2 for a coastline of about 35 km, about which an hydrogeological conceptual model was defined. The area can be conceptualized into three hydrogeological complexes (from the top): sand complex, a clay complex and a sand and conglomerate complex, constituting the deep aquifer, the bottom of which is not well-defined. Shallow aquifer is predominantly fed by direct rainwater infiltration. Deep aquifer is fed by outflows of the mountainous aquifers as the case of limestone aquifer of Pollino Mount,and of shallow granitic aquifer of the Sila massif (Guerricchio and Melidoro, 1975). The maximum piezometric levels of the deep aquifer are equivalent to approximately 40 m asl, so in some areas it presents artesian feature. The computer codes selected for numerical groundwater modelling were MODFLOW (McDonald and Harbaugh, 1998) and SEAWAT (Guo and Langevin, 2002). This groundwater flow modelling is based on the concept of a equivalent homogeneous porous medium by which it is assumed that the real heterogeneous aquifer can be simulated as homogeneous porous media within cells or elements (Anderson, 2002). The modeled aquifer area was uniformly discretized, using Peclet number, into a finite difference grid of 97,735 cells of 240 m x 350 m. For the vertical discretization, model was divided into five layers of variable thicknesses, defined on the basis of a multi-methodological geological survey. Climatic, hydrological and agricultural data were processed to defines inputs for the numerical model based on the variable-density flow. An hydrological balance using monthly and annual of 13 thermo-pluviometric stations falling in the study area, in the time period 1930-1975, was done (Polemio and Casarano, 2008, Polemio et alii, 2013). The numerical model was calibrated with PEST code with a correlation coefficient equal to 0,90. Preliminary results of steady flow and of groundwater salinity spatial are now available and shows it is not sustainable in the case of shallow aquifer and it can be improved in the case of deep aquifer.

Description: Published

Description: Husum (Germany)

Description: 6A. Monitoraggio ambientale, sicurezza e territorio

Description: open