Distribution of calcium-independent phospholipase A2 (iPLA 2) in monkey brain.

The present study was carried out to elucidate the distribution of calcium-independent phospholipase A(2) (iPLA(2)) in the normal monkey brain. iPLA(2) immunoreactivity was observed in structures derived from the telencephalon, including the cerebral neocortex, amygdala, hippocampus, caudate nucleus, putamen, and nucleus accumbens, whereas structures derived from the diencephalon, including the thalamus, hypothalamus and globus pallidus were lightly labeled. The midbrain, vestibular, trigeminal and inferior olivary nuclei, and the cerebellar cortex were densely labeled. Immunoreactivity was observed on the nuclear envelope of neurons, and dendrites and axon terminals at electron microscopy. Western blot analysis showed higher levels of iPLA(2) protein in the cytosolic, than the nuclear fraction, but little or no protein in the membrane fraction. Similarly, subcellular fractionation studies of iPLA(2) activity in rat brain cortical cell cultures showed greater enzymatic activity in the cytosolic, than the nuclear fraction, and the least activity in non-nuclear membranes. The association of iPLA(2) with the nuclear envelope suggests a role of the enzyme in nuclear signaling, such as during neuronal proliferation and differentiation or death. In addition, the localization of iPLA(2) in dendrites and axon terminals suggests a role of the enzyme in neuronal signaling.