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Dubey NK, Mishra S, Goswami C. Progesterone interacts with the mutational hot-spot of TRPV4 and acts as a ligand relevant for fast Ca 2+-signalling. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184178. [PMID: 37225030 DOI: 10.1016/j.bbamem.2023.184178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 05/03/2023] [Accepted: 05/15/2023] [Indexed: 05/26/2023]
Abstract
Steroids are also known to induce immediate physiological and cellular response which occurs within minutes to seconds, or even faster. Such non-genomic actions of steroids are rapid and are proposed to be mediated by different ion channels. Transient receptor potential vanilloid sub-type 4 (TRPV4), is a non-specific polymodal ion channel which is involved in several physiological and cellular processes. In this work, we explored the possibilities of Progesterone (P4) as an endogenous ligand for TRPV4. We demonstrate that P4 docks as well as physically interacts with the TM4-loop-TM5 region of TRPV4, a region which is a mutational hotspot for different diseases. Live cell imaging experiments with a genetically encoded Ca2+-sensor suggests that P4 causes quick influx of Ca2+ specifically in the TRPV4 expressing cells, which can be partially blocked by TRPV4-specific inhibitor, suggesting that P4 can act as a ligand for TRPV4. Such P4-mediated Ca2+-influx is altered in cells expressing disease causing TRPV4 mutants, namely in L596P, R616Q, and also in embryonic lethal mutant L618P. P4 dampens, both in terms of "extent" as well as the "pattern" of the Ca2+-influx by other stimulus too in cells expressing TRPV4-Wt, suggesting that P4 crosstalk with the TRPV4-mediated Ca2+-signalling, both in quick and long-term manner. We propose that P4 crosstalk with TRPV4 might be relevant for both acute and chronic pain as well as for other health-related functions.
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Affiliation(s)
- Nishant Kumar Dubey
- National Institute of Science Education and Research Bhubaneswar, School of Biological Sciences, P.O. Jatni, Khurda 752050, Odisha, India; Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | - Subham Mishra
- National Institute of Science Education and Research Bhubaneswar, School of Biological Sciences, P.O. Jatni, Khurda 752050, Odisha, India; Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | - Chandan Goswami
- National Institute of Science Education and Research Bhubaneswar, School of Biological Sciences, P.O. Jatni, Khurda 752050, Odisha, India; Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India.
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Hernandez CC, Gimenez LE, Dahir NS, Peisley A, Cone RD. The unique structural characteristics of the Kir 7.1 inward rectifier potassium channel: a novel player in energy homeostasis control. Am J Physiol Cell Physiol 2023; 324:C694-C706. [PMID: 36717105 PMCID: PMC10026989 DOI: 10.1152/ajpcell.00335.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 01/12/2023] [Accepted: 01/13/2023] [Indexed: 02/01/2023]
Abstract
The inward rectifier potassium channel Kir7.1, encoded by the KCNJ13 gene, is a tetramer composed of two-transmembrane domain-spanning monomers, closer in homology to Kir channels associated with potassium transport such as Kir1.1, 1.2, and 1.3. Compared with other channels, Kir7.1 exhibits small unitary conductance and low dependence on external potassium. Kir7.1 channels also show a phosphatidylinositol 4,5-bisphosphate (PIP2) dependence for opening. Accordingly, retinopathy-associated Kir7.1 mutations mapped at the binding site for PIP2 resulted in channel gating defects leading to channelopathies such as snowflake vitreoretinal degeneration and Leber congenital amaurosis in blind patients. Lately, this channel's role in energy homeostasis was reported due to the direct interaction with the melanocortin type 4 receptor (MC4R) in the hypothalamus. As this channel seems to play a multipronged role in potassium homeostasis and neuronal excitability, we will discuss what is predicted from a structural viewpoint and its possible implications for hunger control.
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Affiliation(s)
- Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Luis E Gimenez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Naima S Dahir
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Alys Peisley
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Roger D Cone
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States
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Beverley KM, Pattnaik BR. Inward rectifier potassium (Kir) channels in the retina: living our vision. Am J Physiol Cell Physiol 2022; 323:C772-C782. [PMID: 35912989 PMCID: PMC9448332 DOI: 10.1152/ajpcell.00112.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 07/25/2022] [Accepted: 07/25/2022] [Indexed: 11/22/2022]
Abstract
Channel proteins are vital for conducting ions throughout the body and are especially relevant to retina physiology. Inward rectifier potassium (Kir) channels are a class of K+ channels responsible for maintaining membrane potential and extracellular K+ concentrations. Studies of the KCNJ gene (that encodes Kir protein) expression identified the presence of all of the subclasses (Kir 1-7) of Kir channels in the retina or retinal-pigmented epithelium (RPE). However, functional studies have established the involvement of the Kir4.1 homotetramer and Kir4.1/5.1 heterotetramer in Müller glial cells, Kir2.1 in bipolar cells, and Kir7.1 in the RPE cell physiology. Here, we propose the potential roles of Kir channels in the retina based on the physiological contributions to the brain, pancreatic, and cardiac tissue functions. There are several open questions regarding the expressed KCNJ genes in the retina and RPE. For example, why does not the Kir channel subtype gene expression correspond with protein expression? Catching up with multiomics or functional "omics" approaches might shed light on posttranscriptional changes that might influence Kir subunit mRNA translation within the retina that guides our vision.
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Affiliation(s)
- Katie M Beverley
- Endocrinology and Reproductive Physiology Graduate Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
- McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin
| | - Bikash R Pattnaik
- Endocrinology and Reproductive Physiology Graduate Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
- McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
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Beverley KM, Shahi PK, Kabra M, Zhao Q, Heyrman J, Steffen J, Pattnaik BR. Kir7.1 disease mutant T153I within the inner pore affects K+ conduction. Am J Physiol Cell Physiol 2022; 323:C56-C68. [PMID: 35584325 DOI: 10.1152/ajpcell.00093.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Inward-rectifier potassium channel 7.1 (Kir7.1) is present in polarized epithelium, including the RPE. A single amino acid change at position 153 in the KCNJ13 gene, a substitution of threonine to isoleucine in Kir7.1 protein, causes blindness. We hypothesized that the disease caused by this single amino acid substitution within the transmembrane protein domain could alter the translation, localization, or ion transport properties. We assessed the effects of amino acid side-chain length, arrangement, and polarity on channel structure and function. We showed that the T153I mutation yielded a full-length protein localized to the cell membrane. Whole-cell patch-clamp recordings and chord conductance analyses revealed that the T153I mutant channel had negligible K+ conductance and failed to hyperpolarize the membrane potential. However, the mutant channel exhibited enhanced inward current when Rb+ was used as a charge carrier, suggesting that an inner pore had formed, and the channel was dysfunctional. Substituting with a polar, non-polar, or short side-chain amino acid did not affect the localization of the protein. Still, it had an altered channel function due to differences in pore radius. Polar side chains (cysteine and serine) with inner pore radii comparable to wildtype exhibited normal inward K+ conductance. Short side-chains (glycine and alanine) produced a channel with wider than expected inner pore size and lacked the biophysical characteristics of the wildtype channel. Leucine substitution produced results similar to the T153I mutant channel. This study provides direct electrophysiological evidence for the structure and function of the Kir7.1 channel's narrow inner pore in regulating conductance.
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Affiliation(s)
- Katie M Beverley
- Endocrinology and Reproductive Physiology Graduate Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Pawan K Shahi
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Meha Kabra
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Qianqian Zhao
- Department of Biostatistics and Medical Informatics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Joseph Heyrman
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Jack Steffen
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Bikash R Pattnaik
- Endocrinology and Reproductive Physiology Graduate Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States.,Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
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