Document Detail

Inhibition of plasma membrane Ca2+-ATPase by heparin is modulated by potassium.
MedLine Citation:
PMID:  17113336     Owner:  NLM     Status:  MEDLINE    
Heparin is related to several protein receptors that control Ca2+ homeostasis. Here, we studied the effects of heparin on the plasma membrane Ca2+-ATPase from erythrocytes. Both ATP hydrolysis and Ca2+ uptake were inhibited by heparin without modification of the steady-state level of phosphoenzyme formed by ATP. Calmodulin did neither modify the inhibition nor the binding of heparin. Inhibition by heparin was counteracted by K+ but not by Li+. This effect was extended to other sulfated polysaccharides with high number of sulfate residues. Hydrolysis of p-nitrophenylphosphate was equally inhibited by heparin. No evidence for enzyme uncoupling was observed: Ca2+ uptake and ATP hydrolysis remained tightly associated at any level of heparin, and heparin did not increase the passive Ca2+ efflux of inside-out vesicles. Vanadate blocked this efflux, indicating that the main point of Ca2+ escape from these vesicles was linked to the Ca2+ pump. It is discussed that sulfated polysaccharides may physiologically increase the steady-state level of Ca2+ in the cytosol by inhibiting the Ca2+ pumps in a K+ (and tissue) regulated way. It is suggested that heparin regulates the plasma membrane Ca2+-ATPase by binding to the E2 conformer.
Carla F Felix; Vanessa H Oliveira; Otacilio C Moreira; Julio A Mignaco; Hector Barrabin; Helena M Scofano
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-10-21
Journal Detail:
Title:  The international journal of biochemistry & cell biology     Volume:  39     ISSN:  1357-2725     ISO Abbreviation:  Int. J. Biochem. Cell Biol.     Publication Date:  2007  
Date Detail:
Created Date:  2007-01-19     Completed Date:  2007-04-18     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9508482     Medline TA:  Int J Biochem Cell Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  586-96     Citation Subset:  IM    
Instituto de Bioquímica Médica, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ 21941-590, Brazil.
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MeSH Terms
Adenosine Triphosphate / metabolism
Calcium-Transporting ATPases / antagonists & inhibitors*,  blood
Drug Interactions
Enzyme Inhibitors / pharmacology
Erythrocyte Membrane / drug effects*,  enzymology*
Heparin / pharmacology*
Homeostasis / drug effects
Lithium / pharmacology
Polysaccharides / pharmacology
Potassium / pharmacology*
Reg. No./Substance:
0/Enzyme Inhibitors; 0/Polysaccharides; 56-65-5/Adenosine Triphosphate; 7439-93-2/Lithium; 7440-09-7/Potassium; 9005-49-6/Heparin; EC ATPases

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