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Pharmacological Modulation and (Patho)Physiological Roles of TRPM4 Channel-Part 2: TRPM4 in Health and Disease. Pharmaceuticals (Basel) 2021; 15:ph15010040. [PMID: 35056097 PMCID: PMC8779181 DOI: 10.3390/ph15010040] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 12/21/2021] [Accepted: 12/22/2021] [Indexed: 02/06/2023] Open
Abstract
Transient receptor potential melastatin 4 (TRPM4) is a unique member of the TRPM protein family and, similarly to TRPM5, is Ca2+ sensitive and permeable for monovalent but not divalent cations. It is widely expressed in many organs and is involved in several functions; it regulates membrane potential and Ca2+ homeostasis in both excitable and non-excitable cells. This part of the review discusses the currently available knowledge about the physiological and pathophysiological roles of TRPM4 in various tissues. These include the physiological functions of TRPM4 in the cells of the Langerhans islets of the pancreas, in various immune functions, in the regulation of vascular tone, in respiratory and other neuronal activities, in chemosensation, and in renal and cardiac physiology. TRPM4 contributes to pathological conditions such as overactive bladder, endothelial dysfunction, various types of malignant diseases and central nervous system conditions including stroke and injuries as well as in cardiac conditions such as arrhythmias, hypertrophy, and ischemia-reperfusion injuries. TRPM4 claims more and more attention and is likely to be the topic of research in the future.
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Neuland K, Sharma N, Frick M. Synaptotagmin-7 links fusion-activated Ca²⁺ entry and fusion pore dilation. J Cell Sci 2014; 127:5218-27. [PMID: 25344253 PMCID: PMC4265738 DOI: 10.1242/jcs.153742] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Ca(2+)-dependent regulation of fusion pore dilation and closure is a key mechanism determining the output of cellular secretion. We have recently described 'fusion-activated' Ca(2+) entry (FACE) following exocytosis of lamellar bodies in alveolar type II cells. FACE regulates fusion pore expansion and facilitates secretion. However, the mechanisms linking this locally restricted Ca(2+) signal and fusion pore expansion were still elusive. Here, we demonstrate that synaptotagmin-7 (Syt7) is expressed on lamellar bodies and links FACE and fusion pore dilation. We directly assessed dynamic changes in fusion pore diameters by analysing diffusion of fluorophores across fusion pores. Expressing wild-type Syt7 or a mutant Syt7 with impaired Ca(2+)-binding to the C2 domains revealed that binding of Ca(2+) to the C2A domain facilitates FACE-induced pore dilation, probably by inhibiting translocation of complexin-2 to fused vesicles. However, the C2A domain hampered Ca(2+)-dependent exocytosis of lamellar bodies. These findings support the hypothesis that Syt7 modulates fusion pore expansion in large secretory organelles and extend our picture that lamellar bodies contain the necessary molecular inventory to facilitate secretion during the exocytic post-fusion phase. Moreover, regulating Syt7 levels on lamellar bodies appears to be essential in order that exocytosis is not impeded during the pre-fusion phase.
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Affiliation(s)
- Kathrin Neuland
- Institute of General Physiology, University of Ulm, Albert-Einstein Allee 11, 89081 Ulm, Germany
| | - Neeti Sharma
- Institute of General Physiology, University of Ulm, Albert-Einstein Allee 11, 89081 Ulm, Germany
| | - Manfred Frick
- Institute of General Physiology, University of Ulm, Albert-Einstein Allee 11, 89081 Ulm, Germany
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Surfactant secretion in LRRK2 knock-out rats: changes in lamellar body morphology and rate of exocytosis. PLoS One 2014; 9:e84926. [PMID: 24465451 PMCID: PMC3897396 DOI: 10.1371/journal.pone.0084926] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 11/19/2013] [Indexed: 12/16/2022] Open
Abstract
Leucine-rich repeat kinase 2 (LRRK2) is known to play a role in the pathogenesis of various diseases including Parkinson disease, morbus Crohn, leprosy and cancer. LRRK2 is suggested to be involved in a number of cell biological processes such as vesicular trafficking, transcription, autophagy and lysosomal pathways. Recent histological studies of lungs of LRRK2 knock-out (LRRK2 -/-) mice revealed significantly enlarged lamellar bodies (LBs) in alveolar type II (ATII) epithelial cells. LBs are large, lysosome-related storage organelles for pulmonary surfactant, which is released into the alveolar lumen upon LB exocytosis. In this study we used high-resolution, subcellular live-cell imaging assays to investigate whether similar morphological changes can be observed in primary ATII cells from LRRK2 -/- rats and whether such changes result in altered LB exocytosis. Similarly to the report in mice, ATII cells from LRRK2 -/- rats contained significantly enlarged LBs resulting in a >50% increase in LB volume. Stimulation of ATII cells with ATP elicited LB exocytosis in a significantly increased proportion of cells from LRRK2 -/- animals. LRRK2 -/- cells also displayed increased intracellular Ca2+ release upon ATP treatment and significant triggering of LB exocytosis. These findings are in line with the strong Ca2+-dependence of LB fusion activity and suggest that LRRK2 -/- affects exocytic response in ATII cells via modulating intracellular Ca2+ signaling. Post-fusion regulation of surfactant secretion was unaltered. Actin coating of fused vesicles and subsequent vesicle compression to promote surfactant expulsion were comparable in cells from LRRK2 -/- and wt animals. Surprisingly, surfactant (phospholipid) release from LRRK2 -/- cells was reduced following stimulation of LB exocytosis possibly due to impaired LB maturation and surfactant loading of LBs. In summary our results suggest that LRRK2 -/- affects LB size, modulates intracellular Ca2+ signaling and promotes LB exocytosis upon stimulation of ATII cells with ATP.
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Colsoul B, Nilius B, Vennekens R. On the putative role of transient receptor potential cation channels in asthma. Clin Exp Allergy 2009; 39:1456-66. [PMID: 19624522 DOI: 10.1111/j.1365-2222.2009.03315.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The mammalian transient receptor potential (TRP) superfamily consists of 28 mammalian TRP cation channels, which can be subdivided into six main subfamilies: the TRPC ('Canonical'), TRPV ('Vanilloid'), TRPM ('Melastatin'), TRPP ('Polycystin'), TRPML ('Mucolipin') and the TRPA ('Ankyrin') groups. Increasing evidence has accumulated during the previous few years that links TRP channels to the cause of several diseases or to critically influence and/or determine their progress. This review focuses on the possible role of TRP channels in the aetiology of asthmatic lung disease.
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Affiliation(s)
- B Colsoul
- Laboratory Ion Channel Research, Department of Molecular Cell Biology, KU Leuven, Leuven, Belgium
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O'Brodovich H, Yang P, Gandhi S, Otulakowski G. Amiloride-insensitive Na+and fluid absorption in the mammalian distal lung. Am J Physiol Lung Cell Mol Physiol 2008; 294:L401-8. [DOI: 10.1152/ajplung.00431.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The ability of the distal lung epithelia to actively transport Na+, with Cl−and water following, from the alveolar spaces inversely correlates with morbidity and mortality of infants, children, and adults with alveolar pulmonary edema. It is now recognized, in contrast to many other Na+transporting epithelia, that at least half of this active transport is not sensitive to amiloride, which inhibits the epithelial Na+channel. This paper reviews amiloride-insensitive Na+and fluid transport in the mammalian distal lung unit under basal conditions and speculates on potential explanations for this amiloride-insensitive transport. It also provides new information, using primary cultures of rat fetal distal lung epithelia and alveolar type II cells grown under submersion and air-liquid interface culture conditions, regarding putative blockers of this transport.
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Yarishkin OV, Hwang EM, Park JY, Kang D, Han J, Hong SG. Endogenous TRPM4-like channel in Chinese hamster ovary (CHO) cells. Biochem Biophys Res Commun 2008; 369:712-7. [PMID: 18307979 DOI: 10.1016/j.bbrc.2008.02.081] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Accepted: 02/20/2008] [Indexed: 11/17/2022]
Abstract
Chinese hamster ovary (CHO) cells used in many transfection studies have been found to endogenously express channels permeable to monovalent cations, but not to divalent cations. In the presence of intracellular Ca(2+), 23-pS channel with a linear current-voltage (I-V) relationship could be frequently observed in inside-out patches but not in cell-attached patches. The open probability was voltage-dependent, which is higher at positive potentials. The channel was dose-dependently activated by relatively high level of Ca(2+) (EC(50)=1.04+/-0.08 mM), and sensitively inhibited by 100 microM ATP, ADP, AMP, and 1mM spermine. However, ruthenium red (2 microM) had no effect. Reverse transcript polymerase chain reaction (RT-PCR) supported the presence of mRNA encoding TRPM4b channel protein. Western blot assay finally confirmed the presence of this channel protein in membrane fraction of CHO cells. These results provide evidence that CHO cells express an endogenous TRPM4b-like channel, and thereby can be used as a tool to study de novo regulation/modulation of TRPM4 channel.
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Affiliation(s)
- Oleg V Yarishkin
- Department of Physiology, Institute of Health Sciences, and Medical Research Center for Neural Dysfunction, Gyeongsang National University School of Medicine, 90 Chilam, Jinju 660-751, Republic of Korea
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Nilius B, Owsianik G, Voets T, Peters JA. Transient receptor potential cation channels in disease. Physiol Rev 2007; 87:165-217. [PMID: 17237345 DOI: 10.1152/physrev.00021.2006] [Citation(s) in RCA: 1035] [Impact Index Per Article: 60.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The transient receptor potential (TRP) superfamily consists of a large number of cation channels that are mostly permeable to both monovalent and divalent cations. The 28 mammalian TRP channels can be subdivided into six main subfamilies: the TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), and the TRPA (ankyrin) groups. TRP channels are expressed in almost every tissue and cell type and play an important role in the regulation of various cell functions. Currently, significant scientific effort is being devoted to understanding the physiology of TRP channels and their relationship to human diseases. At this point, only a few channelopathies in which defects in TRP genes are the direct cause of cellular dysfunction have been identified. In addition, mapping of TRP genes to susceptible chromosome regions (e.g., translocations, breakpoint intervals, increased frequency of polymorphisms) has been considered suggestive of the involvement of these channels in hereditary diseases. Moreover, strong indications of the involvement of TRP channels in several diseases come from correlations between levels of channel expression and disease symptoms. Finally, TRP channels are involved in some systemic diseases due to their role as targets for irritants, inflammation products, and xenobiotic toxins. The analysis of transgenic models allows further extrapolations of TRP channel deficiency to human physiology and disease. In this review, we provide an overview of the impact of TRP channels on the pathogenesis of several diseases and identify several TRPs for which a causal pathogenic role might be anticipated.
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Affiliation(s)
- Bernd Nilius
- Department of Physiology, Campus Gasthuisberg, KULeuven, Leuven, Belgium.
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Abstract
In the current review we will summarise data from the recent literature describing molecular and functional properties of TRPM4. Together with TRPM5, these channels are up till now the only molecular candidates for a class of non-selective, Ca(2+)-impermeable cation channels which are activated by elevated Ca2+ levels in the cytosol. Apart from intracellular Ca2+, TRPM4 activation is also dependent on membrane potential. Additionally, channel activity is modulated by ATP, phosphatidylinositol bisphosphate (PiP2), protein kinase C (PKC) phosphorylation and heat. The molecular determinants for channel activation, permeation and modulation are increasingly being clarified, and will be discussed here in detail. The physiological role of Ca(2+)-activated non-selective cation channels is unclear, especially in the absence of gene-specific knock-out mice, but evidence indicates a role as a regulator of membrane potential, and thus the driving force for Ca2+ entry from the extracellular medium.
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Affiliation(s)
- R Vennekens
- Laboratory of Physiology, Katholieke Universiteit Leuven, Campus Gasthuisberg O/N1, Herestraat 49-Bus 802, 3000 Leuven, Belgium.
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Nilius B, Vennekens R. From cardiac cation channels to the molecular dissection of the transient receptor potential channel TRPM4. Pflugers Arch 2006; 453:313-21. [PMID: 16680483 DOI: 10.1007/s00424-006-0088-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2006] [Accepted: 04/13/2006] [Indexed: 12/01/2022]
Abstract
In 2006, we celebrate not only the milestone paper on the patch-clamp technique but also the publication of the first single-channel measurements in cardiac cells revealing a Ca(2+)-activated, nonselective cation channel. Considerable effort has been undertaken since this time to identify molecular candidates for this class of cation channels that can be found in a variety of tissues. Recent work has shown that this channel is very likely TRPM4, a member of the TRPM ion channel family. The current review links the epochal Colquhoun et al. paper to the detailed molecular knowledge and structure function aspects of this TRP channel. It will be shown that TRPM4 is a Ca(2+)- and voltage-activated channel, which is dramatically modulated by the phospholipid phosphatidyl inositol bisphosphate (PIP(2)) and belongs to the heat-activated thermoTRPs. A functional hallmark of TRPM4, as for several TRP channels, is a dramatic shift of its voltage dependence towards negative, physiologically meaningful potentials.
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Affiliation(s)
- Bernd Nilius
- Laboratorium voor Fysiologie, Department of Physiology, Campus Gasthuisberg, KU Leuven, Leuven, Belgium.
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Dietl P, Haller T. Exocytosis of lung surfactant: from the secretory vesicle to the air-liquid interface. Annu Rev Physiol 2005; 67:595-621. [PMID: 15709972 DOI: 10.1146/annurev.physiol.67.040403.102553] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Exocytosis is fundamental in biology and requires an orchestra of proteins and other constituents to fuse a vesicle with the plasma membrane. Although the molecular fusion machinery appears to be well conserved in evolution, the process itself varies considerably with regard to the diversity of physico-chemical and structural factors that govern the delay between stimulus and fusion, the expansion of the fusion pore, the release of vesicle content, and, finally, its extracellular dispersion. Exocytosis of surfactant is unique in many of these aspects. This review deals with the secretory pathway of pulmonary surfactant from the type II cell to the air-liquid interface, with focus on the distinct mechanisms and regulation of lamellar body (LB) fusion and release. We also discuss the fate of secreted material until it is rearranged into units that finally function to reduce the surface tension in the lung.
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Affiliation(s)
- Paul Dietl
- Department of General Physiology, University of Ulm, Ulm, D 89069, Germany.
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