Phosphoregulation of K+‐Cl− cotransporter 4 during changes in intracellular Cl− and cell volume |
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| Authors: | Marc J Bergeron Rachelle Frenette‐Cotton Gabriel A Carpentier Michael G Simard Luc Caron Paul Isenring |
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| Institution: | 1. Nephrology Research Group of the CHUQ‐L'H?tel‐Dieu de Québec Institution, Department of Medicine, Faculty of Medicine, Laval University, Québec, Canada G1R 2J6;2. A CIHR Scholar.;3. Holds a CIHR Canadian Research Chair in Molecular Physiology and is Professor of Medicine at Laval University. |
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| Abstract: | It has long been stated that the K+‐Cl? cotransporters (KCCs) are activated during cell swelling through dephosphorylation of their cytoplasmic domains by a protein phosphatase (PP) but that other enzymes are involved by targeting this PP or the KCCs directly. To date, however, the role of signaling intermediates in KCC regulation has been deduced from indirect evidence rather than in vitro phosphorylation studies, and examined after simulation of ion transport through cell swelling or N‐ethylmaleimide treatment. In this study, the oocyte expression system was used to examine the effects of changes in cell volume (CVOL) and intracellular Cl?] (Cl?]i) on the activity and phosphorylation levels (PLEV) of KCC4, and determine whether these effects are mediated by PP1 or phorbol myristate acetate (PMA)‐sensitive effectors. We found that (1) low Cl?]i or low CVOL leads to decreased activity but increased PLEV, (2) high CVOL leads to increased activity but no decrease in PLEV and (3) calyculin A (Cal A) or PMA treatment leads to decreased activity but no increase in PLEV. Thus, we have shown for the first time that one of the KCCs can be regulated through direct phosphorylation, that changes in Cl?]i or CVOL modify the activity of signaling enzymes at carrier sites, and that the effectors directly involved do not include a Cal A‐sensitive PP in contrast to the widely held view. J. Cell. Physiol. 219: 787–796, 2009. © 2009 Wiley‐Liss, Inc. |
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