Structure And Function Of Cytoplasmic Motors

National Institute Of Neurological Disorders And Stroke

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Abstract

TRANSPORT PROJECT[unreadable] [unreadable] The squid giant axon is an important model for understanding axonal transport. Conventional kinesin (Kinesin-1), the founding member of a diverse and functionally important group of molecular motor proteins, was discovered in squid and its role there attributed to the transport of vesicles down axons. Recently we completed an EST (Expressed Sequence Tag) project aimed at identifying other motors in the squid nervous system. Several lines of evidence show that one of the new kinesins that turned up, a Kinesin-3, appears to be the motor actually responsible for axonal transport. Kinesin-1 may make a contribution as well though it is more likely to be involved in other functions such as tensioning or slow transport. Most recently, Kiinesin-3 has been shown to be a primary motor on mitochondria in the squid nervous system. The idea is emerging that the motors for moving organelles, such as Kinesin-3, exist as small pools, mostly attached to the organelles,while the motors that exist in large, soluble pools, such as Kinesin-1 have other functions. Our EST resource has been shared with seventeen laboratories working on squid to study basic and biomedical research. We also used a new technique we developed to label a subpopulation of the fibers in the actin cytoskeleton with photoactivatable-EGFP-actin. This technique allows observation of lateral motions of actin accompanied by synchronous lateral movement and clustering of beta 1 integrins. These results suggest that actin positioning activates integrins to provide a mechanism for cells to seek new adhesion sites and preferred directions of migration.