title: Stimulation of human and mouse erythrocyte Na(+)-K(+)-2Cl(-) cotransport by osmotic shrinkage does not involve AMP-activated protein kinase, but is associated with STE20/SPS1-related proline/alanine-rich kinase activation.
abstract: This study was undertaken to investigate whether the mechanism of increased Na(+)-K(+)-2Cl(-) (NKCC1) cotransporter activity by osmotic shrinkage involved AMP-activated protein kinase (AMPK) activation. AMPK was found to phosphorylate a recombinant GST-dogfish (1-260) NKCC1 fragment at Ser38 and Ser214, corresponding to Ser77 and Ser242 in human NKCC1, respectively. Incubation of human erythrocytes with 20 microM A769662 AMPK activator increased Ser242 NKCC1 phosphorylation but did not stimulate (86)Rb(+) uptake. Under hypertonic conditions in human red blood cells (RBCs) incubated with 0.3 M sucrose, NKCC1 activity increased as measured by bumetanide-sensitive (86)Rb(+) uptake and AMPK was activated. However, there was no effect of AMPKalpha1 deletion in mouse RBCs on the increased rate of (86)Rb(+) uptake induced by hyperosmolarity. AMPK activation by osmotic shrinkage of mouse RBCs was abrogated by 10 microM STO-609 CaMKKbeta inhibitor, but incubation with STO-609 did not affect the increase in (86)Rb(+) uptake induced by hyperosmolarity. Osmotic shrinkage of human and mouse RBCs led to activation loop phosphorylation of the STE20/SPS1-related proline/alanine-rich kinase (SPAK) at Thr233, which was accompanied by phosphorylation of NKCC1 at Thr203/207/212, one of which (Thr207) is responsible for cotransporter activation. Therefore, phosphorylation-induced activation of NKCC1 by osmotic shrinkage does not involve AMPK and is likely to be due to SPAK activation.
authors.affiliation: Université catholique de Louvain and de Duve Institute, Avenue Hippocrate, Brussels, Belgium.
authors.forename: Brice
authors.initials: B
authors.lastname: Sid
authors.forename: Lisa
authors.initials: L
authors.lastname: Miranda
authors.forename: Didier
authors.initials: D
authors.lastname: Vertommen
authors.forename: Benoît
authors.initials: B
authors.lastname: Viollet
authors.forename: Mark H
authors.initials: MH
authors.lastname: Rider
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001713:Biphenyl Compounds; D015153:Blotting, Western; D002034:Bumetanide / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004232:Diuretics / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology; D004912:Erythrocytes / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D011753:Pyrones / Q000494:pharmacology; D012413:Rubidium / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters / Q000097:blood* / Q000235:genetics / Q000502:physiology; D064506:Solute Carrier Family 12, Member 2; D013876:Thiophenes / Q000494:pharmacology; D000099317:Hippo Kinases
chemical_list: D001713:Biphenyl Compounds; D002034:Bumetanide; D017868:Cyclic AMP-Dependent Protein Kinases; D004232:Diuretics; D017346:Protein Serine-Threonine Kinases; D011753:Pyrones; D012413:Rubidium; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D013876:Thiophenes; C578877:SLC12A2 protein, human; C578878:Slc12a2 protein, mouse; C116037:PAS domain kinases; C402650:SLK protein, mouse; D000099317:Hippo Kinases; C512408:4-hydroxy-3-(4-(2-hydroxyphenyl)phenyl)-6-oxo-7H-thieno(2,3-b)pyridine-5-carbonitrile