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Research Papers

Modeling Bidirectional Transport of New and Used Organelles in Fast Axonal Transport in Neurons

[+] Author and Article Information
A. V. Kuznetsov

Department of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh, NC 27695-7910avkuznet@eos.ncsu.edu

J. Heat Transfer 133(1), 011007 (Sep 27, 2010) (9 pages) doi:10.1115/1.4002304 History: Received November 11, 2009; Revised February 08, 2010; Published September 27, 2010; Online September 27, 2010

This paper develops a model for simulating transport of newly synthesized material from the neuron body toward the synapse of the axon as well as transport of misfolded and aggregated proteins back to the neuron body for recycling. The model demonstrates that motor-assisted transport, much similar to diffusion, can occur due to a simple concentration difference between the cell body and the synapse; organelles heading to the synapse do not need to attach preferably to plus-end-directed molecular motors, same as organelles heading to the neuron body for recycling do not need to attach preferably to minus-end-directed molecular motors. The underlying mechanics of molecular-motor-assisted transport is such that organelles would be transported to the right place even if new and used organelles had the same probability of attachment to plus-end-directed (and minus-end-directed) motors. It is also demonstrated that the axon with organelle traps and a region with a reversed microtubule polarity would support much smaller organelle fluxes of both new and used organelles than a healthy axon. The flux of organelles is shown to decrease as the width of organelle traps increases.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

Schematic diagram of a neuron cell with a dendrite and axon; also, a traffic jam in the axon resulting from crowding of organelles at a certain location in the axon

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Figure 2

(a) Kinetic diagram showing various organelle populations and kinetic processes between them, (b) coordinate system for the axon with two vesicle traps, and (c) coordinate system for the healthy axon

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Figure 3

(a) Distributions of the number densities of new and used free organelles with plus-end-directed motors attached to them, n0+new(x) and n0+used(x), and (b) distributions of the number densities of new and used free organelles with minus-end-directed motors attached to them, n0−new(x) and n0−used(x), for a healthy axon and an axon with traps

Grahic Jump Location
Figure 4

(a) Distributions of the number densities of new and used organelles transported on MTs by plus-end-directed motors, n+new(x) and n+used(x), and (b) distributions of the number densities of organelles transported on MTs by minus-end-directed molecular motors, n−new(x) and n−used(x), for a healthy axon and an axon with traps

Grahic Jump Location
Figure 5

(a) Distributions of the flux of new and used organelles due to diffusion, jdiffnew(x) and jdiffused(x), and (b) distributions of the flux of new and used organelles due to motor-driven transport, jmotornew(x) and jmotorused(x), for a healthy axon and an axon with traps

Grahic Jump Location
Figure 6

(a) Distributions of the total number densities of new and used organelles, ntnew(x) and ntused(x), and (b) total flux of organelles, jnew(δ) and jused(δ), versus the width of the trap for a healthy axon and an axon with traps

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