Michaela Auer-Grumbach and colleagues report that missense alterations in the N-terminal ankyrin domain of TRPV4 underlie three distinct autosomal dominant disorders of the peripheral nervous system. Alterations in other regions of TRPV4 have been shown to underlie a family of autosomal dominant skeletal dysplasias, underscoring the marked clinical heterogeneity associated with mutations in this channel. Spinal muscular atrophies (SMA, also known as hereditary motor neuropathies) and hereditary motor and sensory neuropathies (HMSN) are clinically and genetically heterogeneous disorders of the peripheral nervous system. Here we report that mutations in the TRPV4 gene cause congenital distal SMA, scapuloperoneal SMA, HMSN 2C. We identified three missense substitutions (R269H, R315W and R316C) affecting the intracellular N-terminal ankyrin domain of the TRPV4 ion channel in five families. Expression of mutant TRPV4 constructs in cells from the HeLa line revealed diminished surface localization of mutant proteins. In addition, TRPV4-regulated Ca2+ influx was substantially reduced even after stimulation with 4αPDD, a TRPV4 channel-specific agonist, and with hypo-osmotic solution. In summary, we describe a new hereditary channelopathy caused by mutations in TRPV4 and present evidence that the resulting substitutions in the N-terminal ankyrin domain affect channel maturation, leading to reduced surface expression of functional TRPV4 channels.

Chronic thromboembolic pulmonary hypertension (CTEPH) is associated with chronic inflammation but the pathological mechanisms are largely unknown. Our study aimed to simultaneously profile a broad range of cytokines in the supernatant of pulmonary endarterectomy (PEA) surgical material, as well as prospectively in patients with CTEPH to investigate whether circulating cytokines are associated with haemodynamic and physical characteristics of CTEPH patients.Herein, we show that PEA specimens revealed a significant upregulation of interleukin (IL)-6, monocyte chemoattractant protein-1, interferon-γ-induced protein-10 (IP)-10, macrophage inflammatory protein (MIP)1α and RANTES compared to lung tissue from healthy controls.In prospectively collected serum, levels of IL-6, IL-8, IP-10, monokine induced by interferon-γ (MIG) and MIP1α were significantly elevated in CTEPH patients compared to age- and sex-matched healthy controls. In serum of idiopathic pulmonary arterial hypertension (IPAH) patients, only IP-10 and MIG were significantly increased. In CTEPH but not in IPAH, IP-10 was negatively correlated with cardiac index, 6-min walking distance and carbon monoxide diffusion capacity.In vitro, IP-10 significantly increased migration of freshly isolated adventitial fibroblasts.Our study is the first to show that IP-10 secretion is associated with poor pulmonary haemodynamics and physical capacity in CTEPH and might be involved in the pathological mechanism of PEA tissue formation.

Background and Purpose: Heteromerization ofGPCRs is key to the integration of extracellular signals and the subsequent cell response via several mechanisms including heteromer‐selective ligand binding, trafficking and/or downstream signalling. As the lysophosphatidylinositolGPCR55 (GPR55) has been shown to affect the function of the cannabinoid receptor subtype 2 (CB₂receptor) in human neutrophils, we investigated the possible heteromerization ofCB₂receptorswith GPR55.Experimental Approach: The direct interaction of humanGPR55 andCB₂receptors heterologously expressed inHEK293 cells was assessed by co‐immunoprecipitation and bioluminescence resonance energy transfer assays. The effect of cross‐talk on signalling was investigated at downstream levels by label‐free real‐time methods (Epic dynamic mass redistribution andCellKey impedance assays),ERK1/2‐MAPKactivation and gene reporter assays.Key Results: GPR55 andCB₂receptors co‐localized on the surface ofHEK293 cells, co‐precipitated in membrane extracts and formed heteromers in livingHEK293 cells. Whereas heteromerization led to a reduction inGPR55‐mediated activation of transcription factors (nuclear factor of activatedT‐cells,NF‐κBandcAMPresponse element),ERK1/2‐MAPKactivation was potentiated in the presence ofCB₂receptors.CB₂receptor‐mediated signalling was also affected by co‐expression withGPR55. Label‐free assays confirmed cross‐talk between the two receptors.Conclusions and Implications: Heteromers, unique signalling units, form inHEK293 cells expressingGPR55 andCB₂receptors. The signalling by agonists of either receptor was governed (i) by the presence or absence of the partner receptors (with the consequent formation of heteromers) and (ii) by the activation state of the partner receptor.

Pulmonary hypertension (PH) can result in vascular pruning and increased tortuosity of the blood vessels. In this study we examined whether automatic extraction of lung vessels from contrast-enhanced thoracic computed tomography (CT) scans and calculation of tortuosity as well as 3D fractal dimension of the segmented lung vessels results in measures associated with PH. In this pilot study, 24 patients (18 with and 6 without PH) were examined with thorax CT following their diagnostic or follow-up right-sided heart catheterisation (RHC). Images of the whole thorax were acquired with a 128-slice dual-energy CT scanner. After lung identification, a vessel enhancement filter was used to estimate the lung vessel centerlines. From these, the vascular trees were generated. For each vessel segment the tortuosity was calculated using distance metric. Fractal dimension was computed using 3D box counting. Hemodynamic data from RHC was used for correlation analysis. Distance metric, the readout of vessel tortuosity, correlated with mean pulmonary arterial pressure (Spearman correlation coefficient: ρ = 0.60) and other relevant parameters, like pulmonary vascular resistance (ρ = 0.59), arterio-venous difference in oxygen (ρ = 0.54), arterial (ρ = −0.54) and venous oxygen saturation (ρ = −0.68). Moreover, distance metric increased with increase of WHO functional class. In contrast, 3D fractal dimension was only significantly correlated with arterial oxygen saturation (ρ = 0.47). Automatic detection of the lung vascular tree can provide clinically relevant measures of blood vessel morphology. Non-invasive quantification of pulmonary vessel tortuosity may provide a tool to evaluate the severity of pulmonary hypertension. ClinicalTrials.gov NCT01607489

The potassium channel TWIK-related acid sensitive potassium (TASK)-1 channel, together with other potassium channels, controls the low resting tone of pulmonary arteries. The Src family tyrosine kinase (SrcTK) may control potassium channel function in human pulmonary artery smooth muscle cells (hPASMCs) in response to changes in oxygen tension and the clinical use of a SrcTK inhibitor has resulted in partly reversible pulmonary hypertension.This study aimed to determine the role of SrcTK in hypoxia-induced inhibition of potassium channels in hPASMCs.We show that SrcTK is co-localised with the TASK-1 channel. Inhibition of SrcTK decreases potassium current density and results in considerable depolarisation, while activation of SrcTK increases potassium current in patch-clamp recordings. Moderate hypoxia and the SrcTK inhibitor decrease the tyrosine phosphorylation state of the TASK-1 channel. Hypoxia also decreases the level of phospho-SrcTK (tyr419) and reduces the co-localisation of the TASK-1 channel and phospho-SrcTK. Corresponding to this, hypoxia reduces TASK-1 currents before but not after SrcTK inhibition and, in the isolated perfused mouse lung, SrcTK inhibitors increase pulmonary arterial pressure.We propose that the SrcTK is a crucial factor controlling potassium channels, acting as a cofactor for setting a negative resting membrane potential in hPASMCs and a low resting pulmonary vascular tone.