A novel, kinesin-rich preparation derived from squid giant axons

摘要

Almost 20 years ago, Robert Allen and colleagues (1, 2) observed in squid giant axons a relatively large number of "submicroscopic" particles moving with velocities consistent with fast axonal transport. These observations were made with videoenhanced contrast-differential interference contrast microscopy (1), a methodology which had just been developed. The particles were estimated to be 30-50 nm in diameter, and they were proposed to be anatomical correlates of small vesicles apparent in electron micrographs of Hodge and Adelman (3). We recently published additional evidence in support of this view (4). Moreover, we demonstrated with immunocytochemistry that a small fraction of these vesicles contain the delayed rectifier K~+ channel. This channel is also present in the axolemma, where it underlies the repolarization phase of the nerve impulse ("action potential"; 4, 5). These vesicles appear not to be targeted to the axon terminals since they do not contain synaptic vesicle proteins and are not clathrin coated (4, 6). We have developed novel methodology for isolating them from axoplasm (4). The initial step used in these procedures is highlighted in this report.