The Synthesis and Possible Transport of Specific Proteins by Cells Associated with Brain Capillaries

Abstract

Vinblastine causes alterations in the subcellular distribution of certain proteins synthesized by rat telencephalon slices. Proteins in various subcellular fractions were separated according to their MW by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and radioactive proteins were determined by autofluorography. A microvascular fraction contained very high amounts of radioactivity in proteins with a MW of 71,000. At least 1 of these proteins accumulated in the microvascular fraction when the telencephalon slices were incubated in vinblastine. At the same time these proteins became depleted in a myelinated axon fraction, microsomal fraction and soluble/cytosol fraction. Vinblastine also affected the subcellular distribution of some proteins with a WM below 27,000, but unlike the proteins of MW 71,000 none of these were synthesized at very high rates. Vinblastine did not effect the synthesis of protein in telencephalon slices, nor did it alter the subcellular fractionation of particles and organelles from slices. A non-neuronal vinblastine-sensitive protein translocation system is evidently functioning within the cells of the microvascular network in telencephalon slices. At least 1 protein of MW 71,000 and 1 protein with MW below 27,000 are transported on this system.