Translocation of phospholipase A2 from cytosol to membranes in rat brain induced by calcium ions |
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Authors: | Y Yoshihara Y Watanabe |
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Institution: | Department of Neuroscience, Osaka Bioscience Institute, Japan. |
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Abstract: | Phospholipase A2 (PLA2) activities were found in the cytosolic fractions of rat brain. Using the gel filtration chromatography, two major peaks of PLA2 activities were demonstrated: PLA2-H (200-500 kDa) and PLA2-L (100 kDa). PLA2-L was active at both neutral and alkaline pH and absolutely required Ca2+ for the activity, while the activity of PLA2-H was detected only at alkaline pH and independent of Ca2+. The activation of PLA2-L by Ca2+ was biphasic; the first observed at 1-100 microM Ca2+ and the second at 10 mM Ca2+. In the reconstitution system of partially purified PLA2-L and synaptosomal membranes from rat brain, PLA2-L associated with the membranes in a Ca2(+)-dependent manner. The association was completed within 5-10 min at 25 degrees C both at 10 microM and 1 mM Ca2+, though amount of PLA2-L translocated was dependent on Ca2+ concentrations. These results suggest that Ca2+ promotes the translocation of the cytosolic PLA2-L to membranes where phospholipids, substrate of PLA2, are present. |
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