ISSN:
1432-1424
Keywords:
Key words: Okadaic acid — Calyculin A — Magnesium — N-ethylmaleimide — Red blood cells — Protein phosphatase 1 (PP1) — Protein phosphatase 2A (PP2A)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract. An increase in the activity of membrane-associated protein phosphatase type 1 (mb-PP1) is associated with stimulation of erythrocyte K-Cl cotransport (KCC). We have recently proposed that membrane-associated protein phosphatase type 2A (mb-PP2A) is also involved in KCC regulation by cell swelling (Bize et al., 1999. Am. J. Physiol. 277:C899–C912). We used two protein phosphatase inhibitors, okadaic acid (OA) and calyculin A (CalA), and two KCC activating treatments, n-ethylmaleimide (NEM) and Mg i ++-depletion, and determined KCC transport activity and mb-PP1 and mb-PP2A activities. OA, an inhibitor of erythrocyte mb-PP2A, partially prevents stimulation of KCC activity by NEM but not by Mg i ++-depletion. CalA, an inhibitor of both mb-PP1 and mb-PP2A prevents stimulation of KCC activity by both treatments. NEM and Mg i ++-depletion inhibit mb-PP1 activity, suggesting that activation of KCC can take place in the absence of mb-PP1 activation. Mb-PP2A activity is stimulated in NEM-treated cells but not in Mg i ++-depleted cells. In NEM-treated cells, Mg i ++-depletion inhibits both KCC and mb-PP2A. In Mg i ++-depleted cells, NEM does not stimulate KCC or mb-PP2A. The strong correlation between KCC stimulation and mb-PP2A stimulation provides further support to the idea that mb-PP2A plays an important role in KCC regulation. Our results are consistent with the hypothesis that KCC regulation involves at least two distinguishable phosphorylation sites.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002320001109
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