Purification and immunocytochemical detection of a protein that reveals layer V pyramidal cells in the rat cortex

Protein 36 is a soluble protein isolated and purified from a high-speed supernatant fraction from homogenates of rat brain. To identify this protein in the brain, two-dimensional gel electrophoretograms of soluble proteins were prepared. The protein was separated by ion exchange and gel filtration chromatography. The chromatographic fractions were analyzed by two-dimensional electrophoresis. Protein 36 is a homodimer with a molecular weight of 64,000 Da and monomeric weight of 37,000 Da with an isoelectric point of 6.5. A rabbit antibody was raised to this protein. Immunocytochemical studies indicate that protein 36 is localized in large pyramidal cells, dendrites and axons of layer V of the cerebral cortex. The hippocampus contained cells in the stratum radiata and processes in the stratum pyramidalis. A variety of cell types were also observed in the globus pallidus, thalamus and hypothalamus.