KREV-1 PROTEIN IS ABUNDANTLY EXPRESSED IN THE RAT SPINAL-CORD

The Krev-1 gene, which was originally identified as a dominantly funct ioning tumor suppressor gene inducing a flat revertant of a v-K-ras-tr ansformed NIH 3T3 cell line, was abundantly expressed in the mammalian brain [Kitayama et al. (1989) Cell 56, 77-84]. To investigate where K rev-1 and its family ras proteins are distributed in the central nervo us system, we isolated the membrane fractions from several regions of the brain and spinal cord of rats by subcellular fractionation and ana lyzed those proteins by immunoblot analysis with the specific monoclon al antibodies. Krev-1 protein was detected at the highest level in the spinal cord among areas of the central nervous system which included cerebral cortex, cerebellum, hippocampus, and olfactory bulb. On the o ther hand, ras proteins were found at similar levels in these regions. Within the spinal cord, Krev-1 and ras proteins were detected at a co mparable level in the ventral and dorsal parts, while they were much l ess in the dorsal root ganglion than in the spinal cord. They showed t he differential expression during early postnatal development: Krev-1 protein increased and ras proteins were at relatively high levels. Whe n Krev-1 and ras proteins were examined in synaptosomes from the lumba r spinal cord of newborn rats, most of them were detected not in the s ynaptic vesicles but in the synaptic plasma membranes. Krev-1 protein as well as ras proteins might be involved in neuronal functions in the spinal cord such as sensory processing and motor control.