title: Serine/threonine protein phosphatases and regulation of K-Cl cotransport in human erythrocytes.
abstract: Activation of K-Cl cotransport is associated with activation of membrane-bound serine/threonine protein phosphatases (S/T-PPases). We characterize red blood cell S/T-PPases and K-Cl cotransport activity regarding protein phosphatase inhibitors and response to changes in ionic strength and cell size. Protein phosphatase type 1 (PP1) activity is highly sensitive to calyculin A (CalA) but not to okadaic acid (OA). PP2A activity is highly sensitive to CalA and OA. CalA completely inhibits K-Cl cotransport activity, whereas OA partially inhibits K-Cl cotransport. Membrane PP1 and membrane PP2A activities are elevated in cells suspended in hypotonic solutions, where K-Cl cotransport is elevated. Increases in membrane PP1 activity (62 +/- 10% per 100 meq/l) result from decreases in intracellular ionic strength and correlate with increases in K-Cl cotransport activity (54 +/- 10% per 100 meq/l). Increases in membrane PP2A activity (270 +/- 77% per 100 mosM) result from volume increases and also correlate with increases in K-Cl cotransport activity (420 +/- 47% per 100 mosM). The characteristics of membrane-associated PP1 and PP2A are consistent with a role for both phosphatases in K-Cl cotransport activation in human erythrocytes.
authors.affiliation: Children's Hospital, Boston, Massachusetts 02115, USA. bize_i@a1.tch.harvard.edu
authors.forename: I
authors.initials: I
authors.lastname: Bize
authors.forename: B
authors.initials: B
authors.lastname: Güvenç
authors.forename: A
authors.initials: A
authors.lastname: Robb
authors.forename: G
authors.initials: G
authors.lastname: Buchbinder
authors.forename: C
authors.initials: C
authors.lastname: Brugnara
mesh_terms: D000755:Anemia, Sickle Cell / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D048429:Cell Size / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D003681:Dehydration / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000737:chemistry / Q000201:enzymology*; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D008387:Marine Toxins; D008565:Membrane Proteins / Q000378:metabolism; D009761:Nystatin / Q000494:pharmacology; D019319:Okadaic Acid / Q000494:pharmacology; D009994:Osmolar Concentration; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D027981:Symporters; D013912:Threonine / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology*; D000096922:K Cl- Cotransporters
chemical_list: D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007476:Ionophores; D008387:Marine Toxins; D008565:Membrane Proteins; D009761:Nystatin; D019319:Okadaic Acid; D010080:Oxazoles; D010749:Phosphoprotein Phosphatases; D012694:Serine; D027981:Symporters; D013912:Threonine; D000096922:K Cl- Cotransporters; C059041:calyculin A