Ca(2+)-induced reversible translocation of phospholipase A2 between the cytosol and the membrane fraction of rat liver macrophages.
In cell-free extracts of rat liver macrophages (Kupffer cells) phospholipase A2 was found to be rapidly associated with the particulate fraction in a Ca(2+)-dependent manner at Ca2+ concentrations of 0.1-1.0 microM. This is also the range of the levels of intracellular Ca2+ reported for basal and various stimulated conditions. After translocation, phospholipase A2 could be released from the membranes in the presence of Ca2+ chelators, increasing the specific activity of phospholipase A2 in the supernatant fraction. These findings support the view that translocation is a regulatory mechanism of phospholipase A2 by bringing the enzyme to its substrate. Unlike the situation with protein kinase C, Mg2+ exerted little effect on phospholipase A2 translocation, indicating that this process is regulated in vivo mainly by fluctuations of the intracellular Ca2+ content.
Krause
H
H
Biochemisches Institut, Albert-Ludwigs-Universität Freiburg im Breisgau, Federal Republic of Germany.
Dieter
P
P
Schulze-Specking
A
A
Ballhorn
A
A
Decker
K
K
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology; D007700:Kinetics; D007728:Kupffer Cells / Q000201:enzymology*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D051381:Rats; D013379:Substrate Specificity
D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium