Cav2.3 R-type calcium channels: from its discovery to pathogenic de novo CACNA1E variants: a historical perspective.

So-called pharmacoresistant (R-type) voltage-gated Ca2+ channels are structurally only partially characterized. Most of them are encoded by the CACNA1E gene and are expressed as different Cav2.3 splice variants (variant Cav2.3a to Cav2.3e or f) as the ion conducting subunit. So far, no inherited disease is known for the CACNA1E gene but recently spontaneous mutations leading to early death were identified, which will be brought into focus. In addition, a short historical overview may highlight the development to understand that upregulation during aging, easier activation by spontaneous mutations or lack of bioavailable inorganic cations (Zn2+ and Cu2+) may lead to similar pathologies caused by cellular overexcitation.

In vitro and in vivo phosphorylation of the Cav2.3 voltage-gated R-type calcium channel.

During the recording of whole cell currents from stably transfected HEK-293 cells, the decline of currents carried by the recombinant human Cav2.3+ß3 channel subunits is related to adenosine triphosphate (ATP) depletion after rupture of the cells. It reduces the number of functional channels and leads to a progressive shift of voltage-dependent gating to more negative potentials (Neumaier F., et al., 2018). Both effects can be counteracted by hydrolysable ATP, whose protective action is almost completely prevented by inhibition of serine/threonine but not tyrosine or lipid kinases. These findings indicate that ATP promotes phosphorylation of either the channel or an associated protein, whereas dephosphorylation during cell dialysis results in run-down. Protein phosphorylation is required for Cav2.3 channel function and could directly influence the normal features of current carried by these channels. Therefore, results from in vitro and in vivo phosphorylation of Cav2.3 are summarized to come closer to a functional analysis of structural variations in Cav2.3 splice variants.

A practical guide to the preparation and use of metal ion-buffered systems for physiological research.

Recent recognition that mobile pools of Zn2+ and Cu2+ are involved in the regulation of neuronal, endocrine and other cells has stimulated the development of tools to visualize and quantify the level of free trace metal ions. Most of the methods used to measure or control loosely bound metals require reference media that contain exactly defined free concentrations of the target ions. Despite the central importance of proper metal ion buffering, there is still a lack of international standards and beginners in the field may have difficulties finding a coherent description of how to prepare trace metal ion buffers, especially when experiments are to be performed in multimetal systems. To close this gap, we provide a guide for the design, preparation and use of metal ion-buffered systems that facilitate immediate application under physiologically relevant ionic conditions. Thermodynamic and kinetic concepts of chemical speciation as well as general protocols and specific examples are outlined for the accurate preparation of single- and dual-metal ion buffers. In addition, experiments have been performed with FluoZin-3 to illustrate that metal ion-buffered systems are required for reliable preparation of nanomolar Zn2+ solutions and that dual-metal ion buffers can be used to calibrate suitable fluorescent Zn2+ sensors in the presence of millimolar Ca2+ concentrations. Together, the information provided should sensitize readers to the many potential pitfalls and uncertainties that exist when working with physiologically relevant concentrations of trace metal ions and enable them to formulate their own metal ion buffers for most in vitro applications.

R-Type Voltage-Gated Ca²âº Channels in Cardiac and Neuronal Rhythmogenesis.

During the past decades, an increasing number of ion channel and transporter types have been identified acting together to produce cardiac and neuronal pacemaker action potentials. The basis of pacemaker activity was understood in more detail by using single-microelectrode recordings on cells isolated from pacemaker regions. Meanwhile, this powerful technique was complemented by computer modeling and recombinant technologies, including gene inactivation of ion channels and transporters, which may be involved in the generation of the electrical activity of pacemaker cells. Several genes of the voltage-gated Ca(2+) channel (VGCC) family have been ablated, and their role in cardiac and neuronal pacemaking is compared in the present summary, focusing on the role of murine R-type voltage-gated Ca(2+) channels encoded by cacna1e and expressing the ion conducting subunit Cav2.3.

[High frequency oscillation in meconium aspiration and bronchopulmonary dysplasia]. / Hochfrequenzoszillation (HFO) bei Mekoniumaspiration und bei Bronchopulmonaler Dysplasie.

Within one year 3 newborns with meconium-aspiration and 4 infants with bronchopulmonary dysplasia (BPD) were treated with HFP, synchronous with conventional ventilation (CMV). The entrance criteria were insufficient oxygenation (PO2/FiO2 < 50 mmHg) and/or CO2-elimination (> 60 mmHg), respectively peak inspiratory pressure Pi > 40 mmHg and mean airway pressure MAP > 20 mbar during CMV. All three cases of meconium-aspiration have shown a striking improvement in oxygenation and ventilation, in one case starting from a disastrous situation with PCO2 > 90 mmHg, PO2 30 mmHg (FiO2 100%). After a HFO period of 9 to 10 hours Pi, MAP and CMV-frequency could be reduced. The patients could be extubated after 1-2 weeks. In severe BPD only in one case continuous improvement and extubation in the 4. week of life were possible. Here the pulmonary artery pressure in doppler-echocardiography slightly was elevated (30-35 mmHg). In a further case extubation was possible after several trials with HFO. Indeed chronic respiratory insufficiency, progredient pulmonary emphysema on x-ray and clearly elevated pulmonary artery pressure (> 40 mmHg) persisted. In 2 further cases there was no longstanding improvement of ventilation. One child died after 8 months, one after 6 months. In both cases there was a right-to-left shunt over foramen ovale and pulmonary artery pressures at systemic level. HFO led to an improvement in oxygenation and ventilation in all three cases of meconium-aspiration and probably prevented a fatal outcome in one case. The effect seems to depend on improved secretolysis and gas exchange.(ABSTRACT TRUNCATED AT 250 WORDS)