CC BY
21
Abstracts
REGULATION OF CELL VOLUME IN THE LENS: THE ROLE OF CATION CHLORIDE COTRANSPORTERS AND THEIR PHOSPHO-REGULATORS IN MAINTAINING LENS TRANSPARENCY
Vorontsova, I.1' 2, Lim, J.C.1' 2, and Donaldson, P.J.1' 2' 3
1 Department of Optometry and Vision Science, New Zealand
2 National Eye Centre,
3 School of Medical Science, The University of Auckland, Auckland, New Zealand
Lens transparency is dependent on strict cell volume regulation to maintain its highly ordered tissue architecture. In diabetic cataract, cell swelling causes tissue liquefaction and light scattering, resulting in cortical cataract. Elucidating the mechanisms leading to cell volume disruption has identified that members of the Cation Chloride Cotransporter (CCC) family that include the K-Cl-cotransporter (KCC), the Na-K-Cl-cotransporter (NKCC) and the Na-Cl-cotransporter (NCC) play a key role in lens volume regulation [1]. Pharmacological inhibition of KCC, NKCC and activity by DIOA, bumetanide respectively, revealed specific lens damage phenotypes consistent with a role for these transporters in maintaining lens volume regulation under steady state conditions. In other tissues, KCCs and NKCCs are reciprocally regulated by a group of kinases and phosphatases [2-4]. In this study, we utilised RT-PCR, Western blotting and immunohistochemistry to show that the regulatory kinases, With no Lysine Kinase (WNK1, 3, 4), Ste-20 like Proline/Alanine rich Kinase (SPAK) and Oxidative Stress Response Kinase 1 (OSR1) were identified in the rat lens at the transcript and protein level and confirmed the expression of Protein Phosphatas-es PP1 and PP2A in the rat lens. We also show that these phospho-regulatory components are differentially ex-
pressed throughout the lens, with the majority expressed in all regions as peripheral proteins. Furthermore, inhibition of PP1 and PP2A by Okadaic Acid and Calyculin A resulted in cell volume disruption in the lens. Taken together this data reveals that the CCCs are functional in the lens and that their key phospho-regulators are expressed and localised in close proximity to the CCCs whereby they can interact to regulate their activity. As such, this study represents the first link in identifying the cellular mechanisms by which a dysfunction in cell volume regulation may lead to diabetic cataract.
References
1. Chee, K.N., Kistler, J., Donaldson, P.J. Roles for KCC Transporters in the Maintenance of Lens Transparency. Investigative Ophthalmology & Visual Science., 2006, 47 (2), pp. 673-682.
2. Delpire, E., Gagnon, K.B. SPAK and OSR1, key kinases involved in the regulation of chloride transport. Acta Physiologica, 2006, 187 (1-2), pp. 103-113.
3. Kahle, K.T., Ring, A.M., Lifton, R.P. Molecular Physiology of the WNK Kinases. Annual Review of Physiology, 2008, 70 (1), pp. 329-355.
4. Bize, I., Guvenc, B., Robb, A., Buchbinder, G., Brugnara, C. Serine/threonine protein phosphatases and regulation of K-Cl cotransport in human erythrocytes. Am J Physiol Cell Physiol., 1999, 277 (5), C926-36.
68
Бюллетень сибирской медицины, 2013, том 12, № 4, с. 24-68
