1,2,3,4-dithiadiazole derivatives as a novel class of calcium signaling modulators

Aberrant calcium signaling is associated with a diverse range of pathologies, including cardiovascular and neurodegenerative diseases, diabetes, cancer, etc… So, therapeutic strategies based on the correction of pathological calcium signaling are becoming extremely in demand. Thus, the development of novel calcium signaling modulators remains highly actual. Previously we found that 1,2,3,4-dithiadiazole derivative 3-(4-nitrophenyl)-5-phenyl-3H-1,2,3,4-dithiadiazole-2-oxide can strongly reduce calcium uptake through store-operated calcium (SOC) channels. Here we tested several structurally related compounds and found that most of them can effectively affect SOC channels and attenuate calcium content in the endoplasmic reticulum, thus, establishing 1,2,3,4-dithiadiazoles as a novel class of SOC channel inhibitors. Comparing different 1,2,3,4-dithiadiazole derivatives we showed that previously published 3-(4-nitrophenyl)-5-phenyl-3H-1,2,3,4-dithiadiazole-2-oxide and newly tested 3-(3,5-difluorophenyl)-5-phenyl-3H-1,2,3,4-dithiadiazole 2-oxide demonstrated the highest efficacy of SOC entry reduction, supposing the important role of electron-withdrawing substituents to realize the inhibitory activity of 1,2,3,4-dithiadiazoles.

Comparison of the calcium signaling alterations in GABA-ergic medium spiny neurons produced from iPSCs of different origins

Disease models based on induced pluripotent stem cells (iPSCs) are in high demand because of their physiological adequacy and well-reproducibility of the pathological phenotype. Nowadays, the most common approach to generate iPSCs is the reprogramming of somatic cells using vectors based on lentivirus or Sendai virus. We have previously shown impairments of calcium signaling including store-operated calcium entry in Huntington's disease-specific iPSCs-based GABA-ergic medium spiny neurons. However, different approaches for iPSCs generation make it difficult to compare the models since the mechanism of reprogramming may influence the electrophysiological properties of the terminally differentiated neurons. Here, we have studied the features of calcium homeostasis in GABA-ergic medium spiny neurons differentiated from iPSCs obtained from fibroblasts of the same donor using different methods. Our data demonstrated that there were no significant differences neither in calcium influx through the store-operated channels, nor in the levels of proteins activating this type of calcium entry in neurons differentiated from iPSCs generated with lenti- and Sendai viruses-based approaches. We also found no differences in voltage-gated calcium entry for these neurons. Thus, we clearly showed that various methods of cell reprogramming result in similar deregulations in neuronal calcium signaling which substantiates the ability to combine the experimental data on functional studies of ion channels in models based on iPSCs obtained by different methods and expands the prospects for the use of biobanking.

An Efficient 2D Protocol for Differentiation of iPSCs into Mature Postmitotic Dopaminergic Neurons: Application for Modeling Parkinson's Disease

About 15% of patients with parkinsonism have a hereditary form of Parkinson's disease (PD). Studies on the early stages of PD pathogenesis are challenging due to the lack of relevant models. The most promising ones are models based on dopaminergic neurons (DAns) differentiated from induced pluripotent stem cells (iPSCs) of patients with hereditary forms of PD. This work describes a highly efficient 2D protocol for obtaining DAns from iPSCs. The protocol is rather simple, comparable in efficiency with previously published protocols, and does not require viral vectors. The resulting neurons have a similar transcriptome profile to previously published data for neurons, and have a high level of maturity marker expression. The proportion of sensitive (SOX6+) DAns in the population calculated from the level of gene expression is higher than resistant (CALB+) DAns. Electrophysiological studies of the DAns confirmed their voltage sensitivity and showed that a mutation in the PARK8 gene is associated with enhanced store-operated calcium entry. The study of high-purity DAns differentiated from the iPSCs of patients with hereditary PD using this differentiation protocol will allow for investigators to combine various research methods, from patch clamp to omics technologies, and maximize information about cell function in normal and pathological conditions.

The Mystery of EVP4593: Perspectives of the Quinazoline-Derived Compound in the Treatment of Huntington's Disease and Other Human Pathologies

Quinazoline derivatives have various pharmacological activities and are widely used in clinical practice. Here, we reviewed the proposed mechanisms of the physiological activity of the quinazoline derivative EVP4593 and perspectives for its clinical implication. We summarized the accumulated data about EVP4593 and focused on its activities in different models of Huntington's disease (HD), including patient-specific iPSCs-based neurons. To make a deeper insight into its neuroprotective role in HD treatment, we discussed the ability of EVP4593 to modulate calcium signaling and reduce the level of the huntingtin protein. Moreover, we described possible protective effects of EVP4593 in other pathologies, such as oncology, cardiovascular diseases and parasite invasion. We hope that comprehensive analyses of the molecular mechanisms of EVP4593 activity will allow for the expansion of the scope of the EVP4593 application.

STIM2 Mediates Excessive Store-Operated Calcium Entry in Patient-Specific iPSC-Derived Neurons Modeling a Juvenile Form of Huntington's Disease

Huntington's disease (HD) is a severe autosomal-dominant neurodegenerative disorder caused by a mutation within a gene, encoding huntingtin protein. Here we have used the induced pluripotent stem cell technology to produce patient-specific terminally differentiated GABA-ergic medium spiny neurons modeling a juvenile form of HD (HD76). We have shown that calcium signaling is dramatically disturbed in HD76 neurons, specifically demonstrating higher levels of store-operated and voltage-gated calcium uptakes. However, comparing the HD76 neurons with the previously described low-repeat HD models, we have demonstrated that the severity of calcium signaling alterations does not depend on the length of the polyglutamine tract of the mutant huntingtin. Here we have also observed greater expression of huntingtin and an activator of store-operated calcium channels STIM2 in HD76 neurons. Since shRNA-mediated suppression of STIM2 decreased store-operated calcium uptake, we have speculated that high expression of STIM2 underlies the excessive entry through store-operated calcium channels in HD pathology. Moreover, a previously described potential anti-HD drug EVP4593 has been found to attenuate high levels of both huntingtin and STIM2 that may contribute to its neuroprotective effect. Our results are fully supportive in favor of the crucial role of calcium signaling deregulation in the HD pathogenesis and indicate that the cornerstone of excessive calcium uptake in HD-specific neurons is a calcium sensor and store-operated calcium channels activator STIM2, which should become a molecular target for medical treatment and novel neuroprotective drug development.

Store-Operated Calcium Entry in Mouse Cardiomyocytes

The fluorescent dye fura-2 AM was employed to record activation of Ca²⁺ entry in response to a decrease in Ca²⁺ concentration in the endoplasmic reticulum. Using whole-cell voltage clamp technique, we revealed Ca²⁺ currents with an amplitude of 0.46±0.13 pA/pF that passed through selective channels with current-voltage characteristics similar to those of classical store-operated CRAC channels. These currents were sensitive to 2-APB (50 μM), an inhibitor of store-operated channels. The data suggest that store-operated calcium entry is a characteristic feature of mature ventricular cardiomyocytes. Pathological alterations in store-operated Ca²⁺ entry can be implicated in the development of heart diseases.