The health and integrity of photoreceptors critically depend on the composition and volume of their extracellular microenvironment. Regulation of the ionic composition and volume of the subretinal space is accomplished by the transport of ions and water across the retinal pigment epithelium (RPE), a multifunctional monolayer of cells juxtaposed between the photoreceptor outer segments and the choroidal blood supply. RPE transport is the result of the coordinated activity of a diverse group of ion transport proteins and channels residing in its apical and basolateral membranes. With changes in retinal activity, chemical signals released by retinal cells diffuse to the RPE and initiate adjustments in its transport to compensate for alterations in the photoreceptor microenvironment. Disruption of these transport processes or their regulation may cause adverse changes in the subretinal space, contributing to retinal disease. These channels and transporters are also responsible for maintaining the intracellular composition of the RPE cell, which, if disturbed, could adversely affect other key RPE functions such as phagocytosis, the degradation of photoreceptor outer segments, and vitamin A transport and metabolism. Our overall goal is to understand the mechanisms by which potassium (K+) channels participate in the regulation of the volume and ionic composition of the fluid in both the subretinal space and the RPE cytoplasm. Recent studies have identified in the RPE an outwardly rectifying K+ current that resembles the M-type current in neurons.
The specific aims of this proposal are to: (1) determine the subunit composition of KCNQ channels that underlie the M-type conductance in the RPE;(2) determine whether the M-type conductance is localized to the apical or basolateral membrane;(3) determine whether the M-type conductance is modulated by pharmacologic agents and signaling pathways known to modulate specific types of KCNQ channels;and (4) determine the role of the M-type conductance in the regulation of RPE cell volume.
These aims will be pursued using a combination of molecular, biochemical, immunohistochemical, imaging, and electrophysiological techniques to investigate M-type channel structure, function, and regulation. The outcome of these studies will result in a better understanding of how these critically important transport proteins operate in the RPE to help maintain a healthy photoreceptor microenvironment.

Public Health Relevance

The health and integrity of photoreceptors critically depend on the composition and volume of their extracellular microenvironment. Regulation of the ionic composition and volume of the subretinal space is accomplished by the transport of ions and water across the retinal pigment epithelium (RPE), a monolayer of cells juxtaposed between the photoreceptor outer segments and the choroidal blood supply. RPE transport is the result of the coordinated activity of a diverse group of ion transport proteins and channels residing in its membranes. With changes in retinal activity, chemical signals released by retinal cells diffuse to the RPE and initiate adjustments in its transport to compensate for alterations in the photoreceptor microenvironment. Disruption of these transport processes or their regulation may cause adverse changes in the subretinal space, contributing to retinal disease.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY008850-22
Application #
8386602
Study Section
Biology and Diseases of the Posterior Eye Study Section (BDPE)
Program Officer
Neuhold, Lisa
Project Start
1991-01-01
Project End
2014-11-30
Budget Start
2012-12-01
Budget End
2014-11-30
Support Year
22
Fiscal Year
2013
Total Cost
$348,737
Indirect Cost
$123,017
Name
University of Michigan Ann Arbor
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Zhang, Wei; Zhang, Xiaoming; Wang, Hui et al. (2013) Characterization of the R162W Kir7.1 mutation associated with snowflake vitreoretinopathy. Am J Physiol Cell Physiol 304:C440-9
Pattnaik, Bikash R; Hughes, Bret A (2012) Effects of KCNQ channel modulators on the M-type potassium current in primate retinal pigment epithelium. Am J Physiol Cell Physiol 302:C821-33
Zhang, Xiaoming; Yang, Dongli; Hughes, Bret A (2011) KCNQ5/K(v)7.5 potassium channel expression and subcellular localization in primate retinal pigment epithelium and neural retina. Am J Physiol Cell Physiol 301:C1017-26
Yang, Dongli; Elner, Susan G; Clark, Andrea J et al. (2011) Activation of P2X receptors induces apoptosis in human retinal pigment epithelium. Invest Ophthalmol Vis Sci 52:1522-30
Pattnaik, Bikash R; Hughes, Bret A (2009) Regulation of Kir channels in bovine retinal pigment epithelial cells by phosphatidylinositol 4,5-bisphosphate. Am J Physiol Cell Physiol 297:C1001-11
Yang, Dongli; Zhang, Xiaoming; Hughes, Bret A (2008) Expression of inwardly rectifying potassium channel subunits in native human retinal pigment epithelium. Exp Eye Res 87:176-83
Yang, Dongli; Swaminathan, Anuradha; Zhang, Xiaoming et al. (2008) Expression of Kir7.1 and a novel Kir7.1 splice variant in native human retinal pigment epithelium. Exp Eye Res 86:81-91
Hughes, Bret A; Swaminathan, Anuradha (2008) Modulation of the Kir7.1 potassium channel by extracellular and intracellular pH. Am J Physiol Cell Physiol 294:C423-31
Kindzelskii, Andrei L; Elner, Victor M; Elner, Susan G et al. (2004) Human, but not bovine, photoreceptor outer segments prime human retinal pigment epithelial cells for metabolic activation and massive oxidant release in response to lipopolysaccharide and interferon-gamma. Exp Eye Res 79:431-5
Kindzelskii, Andrei L; Elner, Victor M; Elner, Susan G et al. (2004) Toll-like receptor 4 (TLR4) of retinal pigment epithelial cells participates in transmembrane signaling in response to photoreceptor outer segments. J Gen Physiol 124:139-49

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