1
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Kolesnikov DO, Nomerovskaya MA, Grigorieva ER, Reshetin DS, Skobeleva KV, Gusev KO, Shalygin AV, Kaznacheyeva EV. Calcium chelation independent effects of BAPTA on endogenous ANO6 channels in HEK293T cells. Biochem Biophys Res Commun 2024; 693:149378. [PMID: 38100999 DOI: 10.1016/j.bbrc.2023.149378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 12/09/2023] [Indexed: 12/17/2023]
Abstract
Selective calcium chelator 1,2-Bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA) is a common tool to investigate calcium signaling. However, BAPTA expresses various effects on intracellular calcium signaling, which are not related to its ability to bind Ca2+. In patch clamp experiments, we investigated calcium chelation independent effects of BAPTA on endogenous calcium-activated chloride channels ANO6 (TMEM16F) in HEK293T cells. We have found that application of BAPTA to intracellular solution led to two distinct effects on channels properties. On the one hand, application of BAPTA acutely reduced amplitude of endogenous ANO6 channels induced by 10 μM Ca2+ in single channel recordings. On the other hand, BAPTA application by itself induced ANO6 channel activity in the absence of the intracellular calcium elevation. Open channel probability was enhanced by increasing the intracellular BAPTA concentration from 0.1 to 1 and 10 mM. Another calcium chelator EGTA did not demonstrate chelation independent effects on the ANO6 activity in the same conditions. Due to off-target effects BAPTA should be used with caution when studying calcium-activated ANO6 channels.
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Affiliation(s)
- D O Kolesnikov
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - M A Nomerovskaya
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - E R Grigorieva
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - D S Reshetin
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - K V Skobeleva
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - K O Gusev
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - A V Shalygin
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation.
| | - E V Kaznacheyeva
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation.
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2
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Novikova IV, Grekhnev DA, Oshkolova A, Nomerovskaya MA, Kolesnikov DO, Krisanova AV, Yuskovets VN, Chernov NM, Yakovlev IP, Kaznacheyeva EV, Vigont VA. 1,2,3,4-dithiadiazole derivatives as a novel class of calcium signaling modulators. Biochem Biophys Res Commun 2024; 691:149333. [PMID: 38043197 DOI: 10.1016/j.bbrc.2023.149333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 11/08/2023] [Accepted: 11/23/2023] [Indexed: 12/05/2023]
Abstract
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.
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Affiliation(s)
- Iuliia V Novikova
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - Dmitriy A Grekhnev
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - Arina Oshkolova
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - Maria A Nomerovskaya
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - Dmitrii O Kolesnikov
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - Alena V Krisanova
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - Valeriy N Yuskovets
- Organic Chemistry Department, Saint-Petersburg State Chemical Pharmaceutical University, Prof. Popov st. 14, Saint-Petersburg, 197376, Russian Federation
| | - Nikita M Chernov
- Organic Chemistry Department, Saint-Petersburg State Chemical Pharmaceutical University, Prof. Popov st. 14, Saint-Petersburg, 197376, Russian Federation
| | - Igor P Yakovlev
- Organic Chemistry Department, Saint-Petersburg State Chemical Pharmaceutical University, Prof. Popov st. 14, Saint-Petersburg, 197376, Russian Federation
| | - Elena V Kaznacheyeva
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation
| | - Vladimir A Vigont
- Institute of Cytology RAS, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russian Federation.
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3
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Oshkolova AA, Grekhnev DA, Kruchinina AA, Belikova LD, Volovikov EA, Lebedeva OS, Bogomazova AN, Vigont VA, Lagarkova MA, Kaznacheyeva EV. Comparison of the calcium signaling alterations in GABA-ergic medium spiny neurons produced from iPSCs of different origins. Biochimie 2023; 222:63-71. [PMID: 38163516 DOI: 10.1016/j.biochi.2023.12.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 12/27/2023] [Accepted: 12/28/2023] [Indexed: 01/03/2024]
Abstract
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.
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Affiliation(s)
- Arina A Oshkolova
- Institute of Cytology RAS, 194064, Tikhoretsky Ave 4, St. Petersburg, Russia
| | - Dmitriy A Grekhnev
- Institute of Cytology RAS, 194064, Tikhoretsky Ave 4, St. Petersburg, Russia
| | - Anna A Kruchinina
- Institute of Cytology RAS, 194064, Tikhoretsky Ave 4, St. Petersburg, Russia
| | - Lilia D Belikova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435, St. Malaya Pirogovskaya, 1a, Moscow, Russia
| | - Egor A Volovikov
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435, St. Malaya Pirogovskaya, 1a, Moscow, Russia
| | - Olga S Lebedeva
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435, St. Malaya Pirogovskaya, 1a, Moscow, Russia
| | - Alexandra N Bogomazova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435, St. Malaya Pirogovskaya, 1a, Moscow, Russia
| | - Vladimir A Vigont
- Institute of Cytology RAS, 194064, Tikhoretsky Ave 4, St. Petersburg, Russia
| | - Maria A Lagarkova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435, St. Malaya Pirogovskaya, 1a, Moscow, Russia
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4
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Lebedeva OS, Sharova EI, Grekhnev DA, Skorodumova LO, Kopylova IV, Vassina EM, Oshkolova A, Novikova IV, Krisanova AV, Olekhnovich EI, Vigont VA, Kaznacheyeva EV, Bogomazova AN, Lagarkova MA. An Efficient 2D Protocol for Differentiation of iPSCs into Mature Postmitotic Dopaminergic Neurons: Application for Modeling Parkinson's Disease. Int J Mol Sci 2023; 24:ijms24087297. [PMID: 37108456 PMCID: PMC10139404 DOI: 10.3390/ijms24087297] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/31/2023] [Accepted: 04/05/2023] [Indexed: 04/29/2023] Open
Abstract
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.
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Affiliation(s)
- Olga S Lebedeva
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
| | - Elena I Sharova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
| | - Dmitriy A Grekhnev
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Ave 4, 194064 St. Petersburg, Russia
| | - Liubov O Skorodumova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
| | - Irina V Kopylova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
| | - Ekaterina M Vassina
- Vavilov Institute of General Genetics, GSP-1, Gubkina St., 3, 119991 Moscow, Russia
| | - Arina Oshkolova
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Ave 4, 194064 St. Petersburg, Russia
| | - Iuliia V Novikova
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Ave 4, 194064 St. Petersburg, Russia
| | - Alena V Krisanova
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Ave 4, 194064 St. Petersburg, Russia
| | - Evgenii I Olekhnovich
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
| | - Vladimir A Vigont
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Ave 4, 194064 St. Petersburg, Russia
| | - Elena V Kaznacheyeva
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Ave 4, 194064 St. Petersburg, Russia
| | - Alexandra N Bogomazova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
| | - Maria A Lagarkova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, St. Malaya Pirogovskaya, 1a, 119435 Moscow, Russia
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5
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Grekhnev DA, Kruchinina AA, Vigont VA, Kaznacheyeva EV. The Mystery of EVP4593: Perspectives of the Quinazoline-Derived Compound in the Treatment of Huntington's Disease and Other Human Pathologies. Int J Mol Sci 2022; 23:ijms232415724. [PMID: 36555369 PMCID: PMC9778905 DOI: 10.3390/ijms232415724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/06/2022] [Accepted: 12/09/2022] [Indexed: 12/14/2022] Open
Abstract
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.
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6
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Shalygin A, Kolesnikov D, Glushankova L, Gusev K, Skopin A, Skobeleva K, Kaznacheyeva EV. Role of STIM2 and Orai proteins in regulating TRPC1 channel activity upon calcium store depletion. Cell Calcium 2021; 97:102432. [PMID: 34157631 DOI: 10.1016/j.ceca.2021.102432] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Revised: 05/08/2021] [Accepted: 06/04/2021] [Indexed: 11/17/2022]
Abstract
Store-operated calcium channels are the major player in calcium signaling in non-excitable cells. Store-operated calcium entry is associated with the Orai, stromal interaction molecule (STIM), and transient receptor potential canonical (TRPC) protein families. Researchers have provided conflicting data about TRPC1 channel regulation by Orai and STIM. To determine how Orai and STIM influence endogenous TRPC1 pore properties and regulation, we used single channel patch-clamp recordings. Here we showed that knockout or knockdown of Orai1 or Orai3 or overexpression of the dominant-negative mutant Orai1 E106Q did not change the conductance or selectivity of single TRPC1 channels. In addition, these TRPC1 channel properties did not depend on the amount of STIM1 and STIM2 proteins. To study STIM2-mediated regulation of TRPC1 channels, we utilized partial calcium store depletion induced by application of 10 nM thapsigargin (Tg). TRPC1 activation by endogenous STIM2 was greatly decreased in acute extracellular calcium-free experiments. STIM2 overexpression increased both the basal activity and number of silent TRPC1 channels in the plasma membrane. After calcium store depletion, overexpressed STIM2 directly activated TRPC1 in the plasma membrane even without calcium entry in acute experiments. However, this effect was abrogated by co-expression with the non-permeable Orai1 E106Q mutant protein. Taken together, our single-channel patch clamp experiments clearly demonstrated that endogenous TRPC1 forms a channel pore without involving Orai proteins. Calcium entry through Orai triggered TRPC1 channel activation in the plasma membrane, while subsequent STIM2-mediated TRPC1 activity regulation was not dependent on calcium entry.
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Affiliation(s)
- A Shalygin
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia.
| | - D Kolesnikov
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia
| | - L Glushankova
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia
| | - K Gusev
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia
| | - A Skopin
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia
| | - K Skobeleva
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia
| | - E V Kaznacheyeva
- Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia.
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7
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Joshi T, Kumar V, Kaznacheyeva EV, Jana NR. Withaferin A Induces Heat Shock Response and Ameliorates Disease Progression in a Mouse Model of Huntington's Disease. Mol Neurobiol 2021; 58:3992-4006. [PMID: 33904021 DOI: 10.1007/s12035-021-02397-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 04/14/2021] [Indexed: 12/14/2022]
Abstract
Impairment of proteostasis network is one of the characteristic features of many age-related neurodegenerative disorders including autosomal dominantly inherited Huntington's disease (HD). In HD, N-terminal portion of mutant huntingtin protein containing expanded polyglutamine repeats accumulates as inclusion bodies and leads to progressive deterioration of various cellular functioning including proteostasis network. Here we report that Withaferin A (a small bioactive molecule derived from Indian medicinal plant, Withania somnifera) partially rescues defective proteostasis by activating heat shock response (HSR) and delays the disease progression in a HD mouse model. Exposure of Withaferin A activates HSF1 and induces the expression of HSP70 chaperones in an in vitro cell culture system and also suppresses mutant huntingtin aggregation in a cellular model of HD. Withaferin A treatment to HD mice considerably increased their lifespan as well as restored progressive motor behavioral deficits and declined body weight. Biochemical studies confirmed the activation of HSR and global decrease in mutant huntingtin aggregates load accompanied with improvement of striatal function in Withaferin A-treated HD mouse brain. Withaferin A-treated HD mice also exhibit significant decrease in inflammatory processes as evident from the decreased microglial activation. These results indicate immense potential of Withaferin A for the treatment of HD and related neurodegenerative disorders involving protein misfolding and aggregation.
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Affiliation(s)
- Tripti Joshi
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon, 122 051, India
| | - Vipendra Kumar
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon, 122 051, India
| | - Elena V Kaznacheyeva
- Institute of Cytology, Russian Academy of Sciences, 194064, St. Petersburg, Russia
| | - Nihar Ranjan Jana
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon, 122 051, India. .,School of Bioscience, Indian Institute of Technology, Kharagpur, 721302, India.
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Vigont VA, Grekhnev DA, Lebedeva OS, Gusev KO, Volovikov EA, Skopin AY, Bogomazova AN, Shuvalova LD, Zubkova OA, Khomyakova EA, Glushankova LN, Klyushnikov SA, Illarioshkin SN, Lagarkova MA, Kaznacheyeva EV. STIM2 Mediates Excessive Store-Operated Calcium Entry in Patient-Specific iPSC-Derived Neurons Modeling a Juvenile Form of Huntington's Disease. Front Cell Dev Biol 2021; 9:625231. [PMID: 33604336 PMCID: PMC7884642 DOI: 10.3389/fcell.2021.625231] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 01/11/2021] [Indexed: 12/11/2022] Open
Abstract
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.
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Affiliation(s)
- Vladimir A Vigont
- Laboratory of Ionic Channels of Cell Membranes, Department of Molecular Physiology of the Cell, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Dmitriy A Grekhnev
- Laboratory of Ionic Channels of Cell Membranes, Department of Molecular Physiology of the Cell, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Olga S Lebedeva
- Laboratory of Cell Biology, Department of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia.,Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia
| | - Konstantin O Gusev
- Laboratory of Ionic Channels of Cell Membranes, Department of Molecular Physiology of the Cell, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Egor A Volovikov
- Laboratory of Cell Biology, Department of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia
| | - Anton Yu Skopin
- Laboratory of Ionic Channels of Cell Membranes, Department of Molecular Physiology of the Cell, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Alexandra N Bogomazova
- Laboratory of Cell Biology, Department of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia.,Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia
| | - Lilia D Shuvalova
- Laboratory of Cell Biology, Department of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia
| | - Olga A Zubkova
- Laboratory of Cell Biology, Department of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia
| | - Ekaterina A Khomyakova
- Laboratory of Cell Biology, Department of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia
| | - Lyubov N Glushankova
- Laboratory of Ionic Channels of Cell Membranes, Department of Molecular Physiology of the Cell, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | | | | | - Maria A Lagarkova
- Laboratory of Cell Biology, Department of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia.,Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, Russia
| | - Elena V Kaznacheyeva
- Laboratory of Ionic Channels of Cell Membranes, Department of Molecular Physiology of the Cell, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
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9
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Illarioshkin SN, Klyushnikov SA, Vigont VA, Seliverstov YA, Kaznacheyeva EV. Molecular Pathogenesis in Huntington's Disease. Biochemistry (Mosc) 2018; 83:1030-1039. [PMID: 30472941 DOI: 10.1134/s0006297918090043] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Huntington's disease (HD) is a severe autosomal dominant neurodegenerative disorder characterized by a combination of motor, cognitive, and psychiatric symptoms, atrophy of the basal ganglia and the cerebral cortex, and inevitably progressive course resulting in death 5-20 years after manifestation of its symptoms. HD is caused by expansion of CAG repeats in the HTT gene, which leads to pathological elongation of the polyglutamine tract within the respective protein - huntingtin. In this review, we present a modern view on molecular biology of HD as a representative of the group of polyglutamine diseases, with an emphasis on conformational changes of mutant huntingtin, disturbances in its cellular processing, and proteolytic stress in degenerating neurons. Main pathogenetic mechanisms of neurodegeneration in HD are discussed in detail, such as systemic failure of transcription, mitochondrial dysfunction and suppression of energy metabolism, abnormalities of cytoskeleton and axonal transport, microglial inflammation, decrease in synthesis of brain-derived neurotrophic factor, etc.
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Affiliation(s)
| | - S A Klyushnikov
- Research Center of Neurology, Moscow, 125367, Russia.,Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russia
| | - V A Vigont
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russia.
| | | | - E V Kaznacheyeva
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russia.
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Czeredys M, Vigont VA, Boeva VA, Mikoshiba K, Kaznacheyeva EV, Kuznicki J. Huntingtin-Associated Protein 1A Regulates Store-Operated Calcium Entry in Medium Spiny Neurons From Transgenic YAC128 Mice, a Model of Huntington's Disease. Front Cell Neurosci 2018; 12:381. [PMID: 30455632 PMCID: PMC6231533 DOI: 10.3389/fncel.2018.00381] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 10/05/2018] [Indexed: 12/31/2022] Open
Abstract
Huntington's disease (HD) is a hereditary neurodegenerative disease that is caused by polyglutamine expansion within the huntingtin (HTT) gene. One of the cellular activities that is dysregulated in HD is store-operated calcium entry (SOCE), a process by which Ca2+ release from the endoplasmic reticulum (ER) induces Ca2+ influx from the extracellular space. HTT-associated protein-1 (HAP1) is a binding partner of HTT. The aim of the present study was to examine the role of HAP1A protein in regulating SOCE in YAC128 mice, a transgenic model of HD. After Ca2+ depletion from the ER by the activation of inositol-(1,4,5)triphosphate receptor type 1 (IP3R1), we detected an increase in the activity of SOC channels when HAP1 protein isoform HAP1A was overexpressed in medium spiny neurons (MSNs) from YAC128 mice. A decrease in the activity of SOC channels in YAC128 MSNs was observed when HAP1 protein was silenced. In YAC128 MSNs that overexpressed HAP1A, an increase in activity of IP3R1 was detected while the ionomycin-sensitive ER Ca2+ pool decreased. 6-Bromo-N-(2-phenylethyl)-2,3,4,9-tetrahydro-1H-carbazol-1-amine hydrochloride (C20H22BrClN2), identified in our previous studies as a SOCE inhibitor, restored the elevation of SOCE in YAC128 MSN cultures that overexpressed HAP1A. The IP3 sponge also restored the elevation of SOCE and increased the release of Ca2+ from the ER in YAC128 MSN cultures that overexpressed HAP1A. The overexpression of HAP1A in the human neuroblastoma cell line SK-N-SH (i.e., a cellular model of HD (SK-N-SH HTT138Q)) led to the appearance of a pool of constitutively active SOC channels and an increase in the expression of STIM2 protein. Our results showed that HAP1A causes the activation of SOC channels in HD models by affecting IP3R1 activity.
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Affiliation(s)
- Magdalena Czeredys
- Laboratory of Neurodegeneration, International Institute of Molecular and Cell Biology in Warsaw (IIMCB), Warsaw, Poland
| | - Vladimir A Vigont
- Institute of Cytology, Russian Academy of Sciences (RAS), St. Petersburg, Russia
| | - Vasilisa A Boeva
- Institute of Cytology, Russian Academy of Sciences (RAS), St. Petersburg, Russia
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute (BSI), Saitama, Japan
| | - Elena V Kaznacheyeva
- Institute of Cytology, Russian Academy of Sciences (RAS), St. Petersburg, Russia
| | - Jacek Kuznicki
- Laboratory of Neurodegeneration, International Institute of Molecular and Cell Biology in Warsaw (IIMCB), Warsaw, Poland
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Shalygin AV, Kolesnikov D, Skopin A, Perevoznikova A, Glushankova L, Kaznacheyeva EV. Expression Level of STIM Proteins Alter Electrophysiological Properties of Endogenous Calcium Channels. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.1642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Nekrasov ED, Vigont VA, Klyushnikov SA, Lebedeva OS, Vassina EM, Bogomazova AN, Chestkov IV, Semashko TA, Kiseleva E, Suldina LA, Bobrovsky PA, Zimina OA, Ryazantseva MA, Skopin AY, Illarioshkin SN, Kaznacheyeva EV, Lagarkova MA, Kiselev SL. Manifestation of Huntington's disease pathology in human induced pluripotent stem cell-derived neurons. Mol Neurodegener 2016; 11:27. [PMID: 27080129 PMCID: PMC4832474 DOI: 10.1186/s13024-016-0092-5] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 04/08/2016] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Huntington's disease (HD) is an incurable hereditary neurodegenerative disorder, which manifests itself as a loss of GABAergic medium spiny (GABA MS) neurons in the striatum and caused by an expansion of the CAG repeat in exon 1 of the huntingtin gene. There is no cure for HD, existing pharmaceutical can only relieve its symptoms. RESULTS Here, induced pluripotent stem cells were established from patients with low CAG repeat expansion in the huntingtin gene, and were then efficiently differentiated into GABA MS-like neurons (GMSLNs) under defined culture conditions. The generated HD GMSLNs recapitulated disease pathology in vitro, as evidenced by mutant huntingtin protein aggregation, increased number of lysosomes/autophagosomes, nuclear indentations, and enhanced neuronal death during cell aging. Moreover, store-operated channel (SOC) currents were detected in the differentiated neurons, and enhanced calcium entry was reproducibly demonstrated in all HD GMSLNs genotypes. Additionally, the quinazoline derivative, EVP4593, reduced the number of lysosomes/autophagosomes and SOC currents in HD GMSLNs and exerted neuroprotective effects during cell aging. CONCLUSIONS Our data is the first to demonstrate the direct link of nuclear morphology and SOC calcium deregulation to mutant huntingtin protein expression in iPSCs-derived neurons with disease-mimetic hallmarks, providing a valuable tool for identification of candidate anti-HD drugs. Our experiments demonstrated that EVP4593 may be a promising anti-HD drug.
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Affiliation(s)
- Evgeny D. Nekrasov
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119333 Russia
| | - Vladimir A. Vigont
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064 Russia
| | | | - Olga S. Lebedeva
- Scientific-Research Institute of Physical-Chemical Medicine, Moscow, 119435 Russia
| | - Ekaterina M. Vassina
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119333 Russia
| | | | - Ilya V. Chestkov
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119333 Russia
| | - Tatiana A. Semashko
- Scientific-Research Institute of Physical-Chemical Medicine, Moscow, 119435 Russia
| | - Elena Kiseleva
- Federal Research Center Institute of Cytology and Genetics SB RAS, Novosibirsk, 630090 Russia
| | - Lyubov A. Suldina
- Federal Research Center Institute of Cytology and Genetics SB RAS, Novosibirsk, 630090 Russia
| | - Pavel A. Bobrovsky
- Scientific-Research Institute of Physical-Chemical Medicine, Moscow, 119435 Russia
| | - Olga A. Zimina
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064 Russia
| | - Maria A. Ryazantseva
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064 Russia
| | - Anton Yu. Skopin
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064 Russia
| | | | | | - Maria A. Lagarkova
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119333 Russia
- Scientific-Research Institute of Physical-Chemical Medicine, Moscow, 119435 Russia
| | - Sergey L. Kiselev
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119333 Russia
- Kazan State University, Kazan, 420008 Russia
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Ryazantseva MA, Mozhayeva GN, Kaznacheyeva EV. The uncoupling of synaptic protein homer 1c from target proteins activates store-operated calcium entry in a neurotransmitter-like manner in human neuroblastoma cells. Dokl Biol Sci 2013; 450:181-4. [PMID: 23821062 DOI: 10.1134/s001249661303006x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Indexed: 11/22/2022]
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Margulis BA, Vigont V, Lazarev VF, Kaznacheyeva EV, Guzhova IV. Pharmacological protein targets in polyglutamine diseases: mutant polypeptides and their interactors. FEBS Lett 2013; 587:1997-2007. [PMID: 23684638 DOI: 10.1016/j.febslet.2013.05.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 05/06/2013] [Indexed: 12/18/2022]
Abstract
Polyglutamine diseases are a group of pathologies affecting different parts of the brain and causing dysfunction and atrophy of certain neural cell populations. These diseases stem from mutations in various cellular genes that result in the synthesis of proteins with extended polyglutamine tracts. In particular, this concerns huntingtin, ataxins, and androgen receptor. These mutant proteins can form oligomers, aggregates, and, finally, aggresomes with distinct functions and different degrees of cytotoxicity. In this review, we analyze the effects of different forms of polyQ proteins on other proteins and their functions, which are considered as targets for therapeutic intervention.
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Affiliation(s)
- Boris A Margulis
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky pr., 4, St. Petersburg 194064, Russia
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Shalygin AV, Ryazantseva MA, Glushankova LN, Bezprozvanny IB, Mozhayeva GN, Kaznacheyeva EV. Delay in I(min) channel activation induced by dissociation of Homer proteins in A431 cells. Dokl Biol Sci 2011; 438:131-4. [PMID: 21728119 DOI: 10.1134/s0012496611030033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Indexed: 11/22/2022]
Affiliation(s)
- A V Shalygin
- Institute of Cytology, Russian Academy of Sciences, Tikhoretskii pr. 4, St. Petersburg, 194064, Russia
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Shalygin AV, Ryazantseva MA, Glushankova LN, Bezprozvanny IB, Mozhayeva GN, Kaznacheyeva EV. Regulation of Store-Operated Channels by Scaffold Proteins in A431 Cells. Acta Naturae 2010. [DOI: 10.32607/20758251-2010-2-3-94-100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Naumov AP, Kaznacheyeva EV, Kuryshev YA, Mozhayeva GN. Selectivity of ATP-activated GTP-dependent Ca(2+)-permeable channels in rat macrophage plasma membrane. J Membr Biol 1995; 148:91-8. [PMID: 8558606 DOI: 10.1007/bf00234160] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Outside-out configuration of the patch clamp technique was used to test whether an intracellular application of G protein activator (GTP gamma S) affects ATP-activated Ca(2+)-permeable channels in rat macrophages without any agonist in the bath solution. With 145 mM K+ (pCa 8.0) in the pipette solution, activity of channels permeable to a variety of divalent cations and Na+ was observed and general channel characteristics were found to be identical to those of ATP-activated ones. Absence of extracellular ATP makes it possible to avoid the influence of ATP receptor desensitization and to study the channel selectivity using a number of divalent cations (105 mM) and Na+ (145 mM) as the charge carriers. Permeability sequence estimated by extrapolated reversal potential measurements was: Ca2+:Ba2+:Mn2+:Sr2+: Na+:K+ = 68:30:26:10:3.5:1. Slope conductances (in pS) for permeant ions rank as follows: Ca2+:Sr2+: Na+:Mn2+:Ba2+ = 19:18:14:12:10. Unitary Ca2+ currents display a tendency to saturate with the Ca2+ concentration increase with apparent dissociation constant (Kd) of 10 mM. No block of Na+ permeation by extracellular Ca2+ in millimolar range was found. The data obtained suggest that (i) activation of some G protein is sufficient to gate the channels without the ATP receptor being occupied, (ii) the ATP receptor activation results in the gating of a special channel with the properties that differ markedly from those of the receptor-operated or voltage-gated Ca(2+)-permeable channels on the other cell types.
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Affiliation(s)
- A P Naumov
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
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Naumov AP, Kiselyov KI, Mamin AG, Kaznacheyeva EV, Kuryshev YA, Mozhayeva GN. ATP-operated calcium-permeable channels activated via a guanine nucleotide-dependent mechanism in rat macrophages. J Physiol 1995; 486 ( Pt 2):339-47. [PMID: 7473201 PMCID: PMC1156525 DOI: 10.1113/jphysiol.1995.sp020816] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
1. To elucidate the possible involvement of a G protein in ATP-evoked Ca(2+)-permeable channel activity, membrane currents of rat peritoneal macrophages were recorded using inside-out and cell-attached configurations of the patch clamp technique. 2. In inside-out experiments with a pipette solution containing 105 mM Ba2+, application of 100 microM GTP or GTP gamma S to the internal surface of the membrane elicited a rise in channel activity. This effect was observed in 49% of the patches investigated (n = 69). The mean value of NPo (N, number of open channels; Po, channel open probability) was equal to 0.49 +/- 0.27 (mean +/- S.E.M.; n = 16). The delay in the activity development was 21 +/- 8 s (n = 18) with 200 microM ATP added to the pipette solution and about 4 min (n = 5) without agonist in the pipette. Similar results were obtained with 10 mM Ca2+ as the only permeant cation. 3. Properties of GTP gamma S-evoked channels were identical to those of channels activated by extracellular application of ATP. The channels exhibited at least four conductance sublevels, the 4th one being the least frequent. With 105 mM Ba2+ as a permeant cation, sublevel conductances were 3.5, 7, 10 and 15 pS. Corresponding values for 10 mM Ca2+ were about 4, 9, 13 and 17 pS. Extrapolated reversal potential (Er) values were about +40 and +25 mV for Ba2+ and Ca2+, respectively. 4. The activity of channels with similar characteristics could be induced by the extracellular application of fluoride in cell-attached experiments without any agonist in the pipette solution.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A P Naumov
- Institute of Cytology, Russian Academy of Sciences, St Petersburg
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Naumov AP, Kaznacheyeva EV, Kiselyov KI, Kuryshev YA, Mamin AG, Mozhayeva GN. ATP-activated inward current and calcium-permeable channels in rat macrophage plasma membranes. J Physiol 1995; 486 ( Pt 2):323-37. [PMID: 7473200 PMCID: PMC1156524 DOI: 10.1113/jphysiol.1995.sp020815] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
1. To study mechanisms of receptor-operated Ca2+ influx in non-excitable cells, membrane currents of rat peritoneal macrophages were recorded using whole-cell cell-attached and outside-out configurations of the patch clamp technique. Under whole-cell recording conditions, ATP applied in micromolar concentrations elicited an inward current response when the bath solution contained Ba2+, Ca2+ or Na+ as the only permeant cations. 2. Increasing the Mg2+ concentration had an inhibitory effect on the ATP-induced inward current indicating that the active form of ATP responsible for the cation entry is ATP4-. The nucleotide potency order was ATP > ATP gamma S > ADP. UTP was completely ineffective (n = 19). The data obtained are consistent with the ATP receptor being of the P2Z type. 3. The macrophage plasma membrane was impermeable to Tris+ during the ATP-induced current at ATP4- concentrations varying from 0.07 to 500 microM. At higher concentrations, ATP produced a large inward steady-state current, which could be attributed to membrane permeabilization. 4. Activity of single channels was recorded when ATP was applied to the external surface of the patch membrane both in cell-attached and outside-out experiments. A specific property of the channels appeared to be the existence of at least four conductance sublevels. With 105 mM Ba2+ as the permeant cation, the conductance sublevels were 3.5, 7, 10 and 15 pS. With 10 mM Ca2+ the sublevel conductances were equal to 4, 9, 13 and 17 pS. 5. The unitary conductance estimated from the whole-cell current noise analysis (3.5-4.5 pS for 105 mM Ba2+) was significantly lower than that obtained from single channel measurements at the main (3rd) current level, but it was very close to the conductance of the minimum (1st) level. 6. Extrapolated reversal potential values estimated from current-voltage curves for predominant conductance levels were equal to +40 and +26 mV for 105 mM Ba2+ and 10 mM Ca2+, respectively. The permeability ratios fell in the sequence: PCa:PBa:PK = 71.:29:1. Thus, ATP-activated channels in the macrophage membrane are rather selective for divalent vs. monovalent cations, with the predominant permeability being for Ca2+.
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Affiliation(s)
- A P Naumov
- Institute of Cytology, Russian Academy of Sciences, St Petersburg
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Abstract
The patch-clamp technique was used to study mechanisms of ATP-induced Ca2+ influx in rat peritoneal macrophages. The experiments on whole-cell and patch membranes have shown that extracellular ATP activates channels permeable to di- and monovalent inorganic cations. Ratios of unitary channel conductances in 105 mM Ca2+, Sr2+, Mn2+, Ba2+ and normal sodium solutions were 1.0, 0.95, 0.75, 0.55 and 0.85, respectively. The channels could open in the presence of non-hydrolyzable GTP analogues in artificial intracellular solution. The data are consistent with the hypothesis that a GTP-binding protein is involved in receptor-to-channel coupling.
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Affiliation(s)
- A P Naumov
- Institute of Cytology of Russian Academy of Sciences, St. Petersburg
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