Immunolocalization of the sarcolemmal Ca2+/Mg2+ ecto-ATPase (myoglein) in rat myocardium.
Cardiac plasma membrane Ca2+/Mg2+ ecto-ATPase (myoglein) requires millimolar concentrations of either Ca2+ or Mg2+ for maximal activity. In this paper, we report its localization by employing an antiserum raised against the purified rat cardiac Ca2+/Mg2+ ATPase. As assessed by Western blot analysis, the antiserum and the purified immunoglobulin were specific for Ca2+/Mg2+ ecto-ATPase; no cross reaction was observed towards other membrane bound enzymes such as cardiac sarcoplasmic reticulum Ca(2+)-pump ATPase or sarcolemmal Ca(2+)-pump ATPase. On the other hand, the cardiac Ca2+/Mg2+ ecto-ATPase was not recognized by antibodies specific for either cardiac sarcoplasmic reticulum Ca(2+)-pump ATPase or plasma membrane Ca(2+)-pump ATPase. Furthermore, the immune serum inhibited the Ca2+/Mg2+ ecto-ATPase activity of the purified enzyme preparation. Immunofluorescence of cardiac tissue sections and neonatal cultured cardiomyocytes with the Ca2+/Mg2+ ecto-ATPase antibodies indicated the localization of Ca2+/Mg2+ ecto-ATPase in association with the plasma membrane of myocytes, in areas of cell-matrix or cell-cell contact. Staining for the Ca2+/Mg2+ ecto-ATPase was not cardiac specific since the antibodies detected the presence of membrane proteins in sections from skeletal muscle, brain, liver and kidney. The results indicate that Ca2+/Mg2+ ecto-ATPase is localized to the plasma membranes of cardiomyocytes as well as other tissues such as brain, liver, kidney and skeletal muscle.
Kannan
S
S
Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Canada.
Elimban
V
V
Fandrich
R R
RR
Kardami
E
E
Dhalla
N S
NS
D000251:Adenosine Triphosphatases / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D003429:Cross Reactions; D019084:Fluorescent Antibody Technique, Indirect; D007106:Immune Sera; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000201:enzymology*
D007106:Immune Sera; D000251:Adenosine Triphosphatases; C027201:ectoATPase