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The beta(4)-subunit of the large-conductance potassium ion channel K(Ca)1.1 regulates outflow facility in mice

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Title: The beta(4)-subunit of the large-conductance potassium ion channel K(Ca)1.1 regulates outflow facility in mice
Authors: Bertrand, JA
Schicht, M
Stamer, WD
Baker, D
Sherwood, JM
Luetjen-Drecoll, E
Selwood, DL
Overby, DR
Item Type: Journal Article
Abstract: Purpose: The large-conductance calcium-activated potassium channel KCa1.1 (BKCa, maxi-K) influences aqueous humor outflow facility, but the contribution of auxiliary β-subunits to KCa1.1 activity in the outflow pathway is unknown. Methods: Using quantitative polymerase chain reaction, we measured expression of β-subunit genes in anterior segments of C57BL/6J mice (Kcnmb1-4) and in cultured human trabecular meshwork (TM) and Schlemm's canal (SC) cells (KCNMB1-4). We also measured expression of Kcnma1/KCNMA1 that encodes the pore-forming α-subunit. Using confocal immunofluorescence, we visualized the distribution of β4 in the conventional outflow pathway of mice. Using iPerfusion, we measured outflow facility in enucleated mouse eyes in response to 100 or 500 nM iberiotoxin (IbTX; N = 9) or 100 nM martentoxin (MarTX; N = 12). MarTX selectively blocks β4-containing KCa1.1 channels, whereas IbTX blocks KCa1.1 channels that lack β4. Results: Kcnmb4 was the most highly expressed β-subunit in mouse conventional outflow tissues, expressed at a level comparable to Kcnma1. β4 was present within the juxtacanalicular TM, appearing to label cellular processes connecting to SC cells. Accordingly, KCNMB4 was the most highly expressed β-subunit in human TM cells, and the sole β-subunit in human SC cells. To dissect functional contribution, MarTX decreased outflow facility by 35% (27%, 42%; mean, 95% confidence interval) relative to vehicle-treated contralateral eyes, whereas IbTX reduced outflow facility by 16% (6%, 25%). Conclusions: The β4-subunit regulates KCa1.1 activity in the conventional outflow pathway, significantly influencing outflow function. Targeting β4-containing KCa1.1 channels may be a promising approach to lower intraocular pressure to treat glaucoma.
Issue Date: 1-Mar-2020
Date of Acceptance: 9-Jan-2020
URI: http://hdl.handle.net/10044/1/82336
DOI: 10.1167/iovs.61.3.41
ISSN: 0146-0404
Publisher: Association for Research in Vision and Ophthalmology
Journal / Book Title: Investigative Ophthalmology and Visual Science
Volume: 61
Issue: 3
Copyright Statement: © 2020 The Authors. This work is licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/)
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
National Institutes of Health
Royal Academy Of Engineering
Fight for Sight
Funder's Grant Number: EP/J010499/1
203-1774
BMPF_P67271
000028534/534505
Keywords: Science & Technology
Life Sciences & Biomedicine
Ophthalmology
trabecular meshwork
outflow facility
ion channels
mechanotransduction
mouse models
MAXI-K-CHANNELS
BOVINE TRABECULAR MESHWORK
AQUEOUS-HUMOR OUTFLOW
ENDOTHELIAL-CELLS
INTRAOCULAR-PRESSURE
NITRIC-OXIDE
MARTENTOXIN
VOLUME
CULTURE
MODULATION
Adult
Animals
Aqueous Humor
Cells, Cultured
Gene Expression Regulation
Humans
Infant
Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
Large-Conductance Calcium-Activated Potassium Channel beta Subunits
Limbus Corneae
Mice
Mice, Inbred C57BL
Microscopy, Fluorescence
Middle Aged
Nerve Tissue Proteins
Porins
Real-Time Polymerase Chain Reaction
Toxins, Biological
Trabecular Meshwork
Aqueous Humor
Limbus Corneae
Trabecular Meshwork
Cells, Cultured
Animals
Mice, Inbred C57BL
Humans
Mice
Porins
Nerve Tissue Proteins
Microscopy, Fluorescence
Gene Expression Regulation
Adult
Middle Aged
Infant
Toxins, Biological
Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
Large-Conductance Calcium-Activated Potassium Channel beta Subunits
Real-Time Polymerase Chain Reaction
Science & Technology
Life Sciences & Biomedicine
Ophthalmology
trabecular meshwork
outflow facility
ion channels
mechanotransduction
mouse models
MAXI-K-CHANNELS
BOVINE TRABECULAR MESHWORK
AQUEOUS-HUMOR OUTFLOW
ENDOTHELIAL-CELLS
INTRAOCULAR-PRESSURE
NITRIC-OXIDE
MARTENTOXIN
VOLUME
CULTURE
MODULATION
Ophthalmology & Optometry
06 Biological Sciences
11 Medical and Health Sciences
Publication Status: Published
Open Access location: https://doi.org/10.1167/iovs.61.3.41
Article Number: ARTN 41
Appears in Collections:Bioengineering



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