Date

May 2012

Document Type

Dissertation

Degree Name

Ph.D.

Institution

Oregon Health & Science University

Abstract

The ability of a cell to transport cargo vesicles to their correct destination is called selective transport. Neurons, like other cells, require this system in order to develop and function properly. The neuron‘s primary function is to send and receive signals. In order to do so, neurons have developed specialized domains, namely, the axons and dendrites. Both domains require a specific complement of proteins in order to carry out its function. The focus of this work is the underlying mechanism that is responsible for selective vesicle transport in neurons. Kinesin-mediated transport has been implicated in the selective transport of dendritic vesicles, but the mechanism for this is not understood. In this thesis, I present evidence that KIF13B from the Kinesin-3 family is a dendrite-selective kinesin. Expression of GFP-tagged Kinesin-3 family members revealed that while all constructs labeled moving vesicles, KIF13B was unique in that it was the only family member to label vesicles that trafficked exclusively in dendrites. KIF13B is the first kinesin to demonstrate this transport characteristic and further investigation may yield insight toward a mechanism for dendrite-selective transport. I investigated the contribution of the motor domain of KIF13B and its other regions in selective transport using a cell-based transport assay. I found that the motor domain is not sufficient for dendrite selective transport. In addition, I found that other regions within KIF13B were not able to confine transport to the dendrites. This work points towards the conclusion that KIF13B must act in concert with other elements in order for it to act as a selective dendritic motor. To investigate what these other elements may be, I collaborated with other members of the Banker lab to develop a novel assay that identified the kinesins that mediate dendrite-selective transport. We prepared a library of "split kinesins", comprising an axon-selective kinesin motor domain and a series of kinesin tail domains that can attach to their native vesicles. When the split kinesins are assembled by chemical dimerization, bound vesicles are misdirected into the axon. Three Kinesin-3 family members--KIF1A, KIF13A, and KIF13B--interacted with dendritic vesicle populations in the split kinesin assay. KIF1A and KIF13A also bound vesicles that translocate into the axon. These results demonstrate that kinesins play an integral role in dendrite-selective transport and that their transport selectivity is differentially regulated when they bind different vesicular cargoes. Identifying these kinesins and further exploring the proteins they interact with will help in our understanding of dendrite-selective transport and perhaps lead to a mechanism by which this is regulated. Finally, I will discuss specific models that could account for the selectivity of KIF13B-mediated transport, and propose experiments to test the accuracy of these models.

Identifier

doi:10.6083/M48P5XJF

Division

Neuroscience Graduate Program

School

School of Medicine

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