Axonal tubulin and axonal microtubules: biochemical evidence for cold stability.

Abstract

Nerve extracts containing tubulin labeled by axonal transport were analyzed by electrophoresis and differential extraction. A substantial fraction of the tubulin in the axons of the retinal ganglion cell of guinea pigs is not solubilized by conventional methods for preparation of microtubules from whole brain. In 2-dimensional polyacrylamide gel electrophoresis this cold-insoluble tubulin was biochemically distinct from tubulin obtained from whole brain microtubules prepared by cold cycling. Cleveland peptide maps also indicated some differences between the cold-extractable and cold-insoluble tubulins. The demonstration of cold-insoluble tubulin that is specifically axonal in origin permits consideration of the physiological role of cold-insoluble tubulin in a specific cellular structure. Much of this material could be in the form of cold-stable microtubules. The physiological role of cold-insoluble tubulin in the axon may be associated with the regulation of the axonal microtubule complexes in neurons.