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Canella R, Brugnoli F, Gallo M, Keillor JW, Terrazzan A, Ferrari E, Grassilli S, Gates EWJ, Volinia S, Bertagnolo V, Bianchi N, Bergamini CM. A Multidisciplinary Approach Establishes a Link between Transglutaminase 2 and the Kv10.1 Voltage-Dependent K + Channel in Breast Cancer. Cancers (Basel) 2022; 15:cancers15010178. [PMID: 36612174 PMCID: PMC9818547 DOI: 10.3390/cancers15010178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 12/15/2022] [Accepted: 12/24/2022] [Indexed: 12/29/2022] Open
Abstract
Since the multifunctionality of transglutaminase 2 (TG2) includes extra- and intracellular functions, we investigated the effects of intracellular administration of TG2 inhibitors in three breast cancer cell lines, MDA-MB-231, MDA-MB-436 and MDA-MB-468, which are representative of different triple-negative phenotypes, using a patch-clamp technique. The first cell line has a highly voltage-dependent a membrane current, which is low in the second and almost absent in the third one. While applying a voltage protocol to responsive single cells, injection of TG2 inhibitors triggered a significant decrease of the current in MDA-MB-231 that we attributed to voltage-dependent K+ channels using the specific inhibitors 4-aminopyridine and astemizole. Since the Kv10.1 channel plays a dominant role as a marker of cell migration and survival in breast cancer, we investigated its relationship with TG2 by immunoprecipitation. Our data reveal their physical interaction affects membrane currents in MDA-MB-231 but not in the less sensitive MDA-MB-436 cells. We further correlated the efficacy of TG2 inhibition with metabolic changes in the supernatants of treated cells, resulting in increased concentration of methyl- and dimethylamines, representing possible response markers. In conclusion, our findings highlight the interference of TG2 inhibitors with the Kv10.1 channel as a potential therapeutic tool depending on the specific features of cancer cells.
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Affiliation(s)
- Rita Canella
- Department of Neuroscience and Rehabilitation, University of Ferrara, 44121 Ferrara, Italy
| | - Federica Brugnoli
- Department of Translational Medicine, University of Ferrara, 44121 Ferrara, Italy
| | - Mariana Gallo
- Department of Medicine and Surgery, University of Parma, 43125 Parma, Italy
| | - Jeffrey W. Keillor
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Anna Terrazzan
- Department of Translational Medicine, University of Ferrara, 44121 Ferrara, Italy
| | - Elena Ferrari
- Department of Medicine and Surgery, University of Parma, 43125 Parma, Italy
| | - Silvia Grassilli
- Department of Translational Medicine, University of Ferrara, 44121 Ferrara, Italy
| | - Eric W. J. Gates
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Stefano Volinia
- Department of Translational Medicine, University of Ferrara, 44121 Ferrara, Italy
| | - Valeria Bertagnolo
- Department of Translational Medicine, University of Ferrara, 44121 Ferrara, Italy
| | - Nicoletta Bianchi
- Department of Translational Medicine, University of Ferrara, 44121 Ferrara, Italy
- Correspondence: ; Tel.: +39-0532-455854
| | - Carlo M. Bergamini
- Department of Neuroscience and Rehabilitation, University of Ferrara, 44121 Ferrara, Italy
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Abstract
The pancreatic β-cell secretes insulin in response to elevated plasma glucose. This review applies an external bioenergetic critique to the central processes of glucose-stimulated insulin secretion, including glycolytic and mitochondrial metabolism, the cytosolic adenine nucleotide pool, and its interaction with plasma membrane ion channels. The control mechanisms responsible for the unique responsiveness of the cell to glucose availability are discussed from bioenergetic and metabolic control standpoints. The concept of coupling factor facilitation of secretion is critiqued, and an attempt is made to unravel the bioenergetic basis of the oscillatory mechanisms controlling secretion. The need to consider the physiological constraints operating in the intact cell is emphasized throughout. The aim is to provide a coherent pathway through an extensive, complex, and sometimes bewildering literature, particularly for those unfamiliar with the field.
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Affiliation(s)
- David G Nicholls
- Buck Institute for Research on Aging, Novato, California; and Department of Clinical Sciences, Unit of Molecular Metabolism, Lund University Diabetes Centre, Malmo, Sweden
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Jung SC, Eun SY. Sustained K(+) Outward Currents are Sensitive to Intracellular Heteropodatoxin2 in CA1 Neurons of Organotypic Cultured Hippocampi of Rats. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2012; 16:343-8. [PMID: 23118559 PMCID: PMC3484520 DOI: 10.4196/kjpp.2012.16.5.343] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 10/05/2012] [Accepted: 10/10/2012] [Indexed: 11/15/2022]
Abstract
Blocking or regulating K+ channels is important for investigating neuronal functions in mammalian brains, because voltage-dependent K+ channels (Kv channels) play roles to regulate membrane excitabilities for synaptic and somatic processings in neurons. Although a number of toxins and chemicals are useful to change gating properties of Kv channels, specific effects of each toxin on a particular Kv subunit have not been sufficiently demonstrated in neurons yet. In this study, we tested electrophysiologically if heteropodatoxin2 (HpTX2), known as one of Kv4-specific toxins, might be effective on various K+ outward currents in CA1 neurons of organotypic hippocampal slices of rats. Using a nucleated-patch technique and a pre-pulse protocol in voltage-clamp mode, total K+ outward currents recorded in the soma of CA1 neurons were separated into two components, transient and sustained currents. The extracellular application of HpTX2 weakly but significantly reduced transient currents. However, when HpTX2 was added to internal solution, the significant reduction of amplitudes were observed in sustained currents but not in transient currents. This indicates the non-specificity of HpTX2 effects on Kv4 family. Compared with the effect of cytosolic 4-AP to block transient currents, it is possible that cytosolic HpTX2 is pharmacologically specific to sustained currents in CA1 neurons. These results suggest that distinctive actions of HpTX2 inside and outside of neurons are very efficient to selectively reduce specific K+ outward currents.
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Affiliation(s)
- Sung-Cherl Jung
- Department of Physiology, School of Medicine, Jeju National University, Jeju 690-756, Korea
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Willenborg M, Belz M, Schumacher K, Paufler A, Hatlapatka K, Rustenbeck I. Ca(2+)-dependent desensitization of insulin secretion by strong potassium depolarization. Am J Physiol Endocrinol Metab 2012; 303:E223-33. [PMID: 22550068 DOI: 10.1152/ajpendo.00010.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Depolarization by a high K(+) concentration is a widely used experimental tool to stimulate insulin secretion. The effects occurring after the initial rise in secretion were investigated here. After the initial peak a fast decline occurred, which was followed by a slowly progressive decrease in secretion when a strong K(+) depolarization was used. At 40 mM KCl, but not at lower concentrations, the decrease continued when the glucose concentration was raised from 5 to 10 mM, suggesting an inhibitory effect of the K(+) depolarization. When tolbutamide was added instead of the glucose concentration being raised, a complete inhibition down to prestimulatory values was observed. Equimolar reduction of the NaCl concentration to preserve isoosmolarity enabled an increase in secretion in response to glucose. Unexpectedly, the same was true when the Na(+)-reduced media were made hyperosmolar by choline chloride or mannitol. The insulinotropic effect of tolbutamide was not rescued by the compensatory reduction of NaCl, suggesting a requirement for activated energy metabolism. These inhibitory effects could not be explained by a lack of depolarizing strength or by a diminished free cytosolic Ca(2+) concentration ([Ca(2+)](i)). Rather, the complexation of extracellular Ca(2+) concomitant with the K(+) depolarization markedly diminished [Ca(2+)](i) and attenuated the inhibitory action of 40 mM KCl. This suggests that a strong but not a moderate depolarization by K(+) induces a [Ca(2+)](i)-dependent, slowly progressive desensitization of the secretory machinery. In contrast, the decline immediately following the initial peak of secretion may result from the inactivation of voltage-dependent Ca(2+) channels.
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Affiliation(s)
- M Willenborg
- Institute of Pharmacology and Toxicology, University of Braunschweig, Braunschweig, Germany
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Braun M, Rorsman P. The glucagon-producing alpha cell: an electrophysiologically exceptional cell. Diabetologia 2010; 53:1827-30. [PMID: 20556353 DOI: 10.1007/s00125-010-1823-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 05/19/2010] [Indexed: 10/19/2022]
Abstract
Activation of potassium channels normally serves to reduce cellular activity but recent data indicate that the glucagon-secreting alpha cells are different in this respect and that inhibition of voltage-gated potassium channels results in a paradoxical inhibition of glucagon secretion. Here we discuss these findings and attempt to provide a model for the regulation of glucagon secretion that incorporates these observations.
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Affiliation(s)
- M Braun
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
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