Switching of platelet-activating factor acetylhydrolase catalytic subunits in developing rat brain

In a previous study, we demonstrated that Platelet-activating Factor (PAF) acetylhydrolase purified from bovine brain cortical cytosol consists of two mutually homologous catalytic subunits(α1 and α2) and one putative regulatory β subunit. The latter is a product of the LIS1 gene, which is defective in the Miller-Dicker syndrome, a form of lissencephaly. In this study, we examined the expression patterns of these three subunits in the developing rat brain. All three subunits were expressed in embryonic brain, whereas only α2 and β subunit were detected in the adult brain by Western blotting. Biochemical analyses revealed that the α1/α2 heterodimer and α2/α2 homodimer are major catalytic units of embryonic and adult brain PAF acetylhydrolases, respectively. The α1 transcript and protein were detected predominantly in embryonic and postnatal neural tissues, such as the brain and spinal cord. Furthermore, we found using primary cultured cells isolated from neonatal rat brain that α1 protein were expressed only in neurons but not in glial cells and fibroblasts. In contrast, α2 and β transcripts and proteins were detected both in neural and non-neural tissues, and their expression level was almost constant from fetal stages through adulthood. These results indicate that α1 expression is restricted to actively migrating neurons in rats and that switching of catalytic subunits from the α1/α2 heterodimer to the α2/α2 homodimer occurred in these cells during brain development, suggesting that PAF acetylhydrolase plays a role(s) in neuronal migration.