Subcellular Distribution of Proteins Synthesized in Slices of Rat Cerebral Cortex

Abstract

Abstract The incorporation of l-[4,5-3H]leucine into slices of rat cerebral cortex has been measured, with emphasis on the time course of the distribution of label in subcellular fractions prepared by zonal isopycnic centrifugation in continuous sucrose gradients. Rapidly labeled proteins are found in both the soluble and membranous components of the nerve end particles. Except for a minor part of the mitochondrial protein, the synthesis of all membrane-bound proteins is inhibited drastically by cycloheximide. When synthesis is blocked by cycloheximide, the supply of label continues for some minutes to certain membrane fractions derived from synaptic structures, apparently by a rapid transport of newly synthesized proteins from cytoplasmic ribosomes in the neuronal perikaryon. An increased extracellular concentration of potassium ion inhibits and ouabain accelerates protein synthesis in some fractions. These effects suggest a coupling of the protein synthesizing system with the (Na+ + K+)-activated ouabain-sensitive adenosine triphosphatase in the plasma membranes.