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High-resolution imaging reveals indirect coordination of opposite motors and a role for LIS1 in high-load axonal transport.

Yi JY, Ori-McKenney KM, McKenney RJ, Vershinin M, Gross SP, Vallee RB - J. Cell Biol. (2011)

Bottom Line: The specific physiological roles of dynein regulatory factors remain poorly understood as a result of their functional complexity and the interdependence of dynein and kinesin motor activities.Acute dynein inhibition in nonneuronal cells caused an immediate dispersal of diverse forms of cargo, resulting from a sharp decrease in microtubule minus-end run length followed by a gradual decrease in plus-end runs.Our acute inhibition results argue against direct mechanical activation of opposite-directed motors and offer a novel approach of potential broad utility in the study of motor protein function in vivo.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pathology and Cell Biology, Columbia University, New York, NY 10027, USA.

ABSTRACT
The specific physiological roles of dynein regulatory factors remain poorly understood as a result of their functional complexity and the interdependence of dynein and kinesin motor activities. We used a novel approach to overcome these challenges, combining acute in vivo inhibition with automated high temporal and spatial resolution particle tracking. Acute dynein inhibition in nonneuronal cells caused an immediate dispersal of diverse forms of cargo, resulting from a sharp decrease in microtubule minus-end run length followed by a gradual decrease in plus-end runs. Acute LIS1 inhibition or LIS1 RNA interference had little effect on lysosomes/late endosomes but severely inhibited axonal transport of large, but not small, vesicular structures. Our acute inhibition results argue against direct mechanical activation of opposite-directed motors and offer a novel approach of potential broad utility in the study of motor protein function in vivo. Our data also reveal a specific but cell type-restricted role for LIS1 in large vesicular transport and provide the first quantitative support for a general role for LIS1 in high-load dynein functions.

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Effect of LIS1 inhibition on lyso/LE transport in neurons. Control hippocampal and neocortical neurons exhibited rapid lysos/LEs mostly in the retrograde direction. LIS1 inhibition specifically and potently blocked movement of large lysos/LEs, especially at axonal bends and branch points, with little effect on the smaller vesicular transport. These effects were not observed in nonneuronal cells, which is consistent with a role for LIS1 in transport under higher resistance conditions. Red dots indicate lyso/LE particles. Blue arrows indicate transport directions.
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fig5: Effect of LIS1 inhibition on lyso/LE transport in neurons. Control hippocampal and neocortical neurons exhibited rapid lysos/LEs mostly in the retrograde direction. LIS1 inhibition specifically and potently blocked movement of large lysos/LEs, especially at axonal bends and branch points, with little effect on the smaller vesicular transport. These effects were not observed in nonneuronal cells, which is consistent with a role for LIS1 in transport under higher resistance conditions. Red dots indicate lyso/LE particles. Blue arrows indicate transport directions.

Mentions: Together, our results support a requirement for LIS1 in high-load forms of dynein transport. We argue that the large lysos/LEs must be under LIS1 control even when traveling at high rates. This observation has the important consequence that LIS1 must be continuously active during high-speed stepping of dynein along the axonal microtubules. The nature of the resistance encountered by the larger lysos/LEs in our study is uncertain but likely involves local cytoplasmic constrictions, obstructions, or regions of higher viscosity (Figs. 3 B and 5). In this view, oscillations could reflect repeated efforts to bypass these impediments. The extent to which microtubule plus-end–directed kinesins contribute to these behaviors also remains to be explored further. Our results identify a novel conditional role for LIS1 in axonal transport. Mutations in cytoplasmic dynein, which affect vesicular transport, also result in neurodegeneration (Ori-McKenney et al., 2010). Whether similar effects will be found for the LIS1 gene remains an important issue for further investigation.


High-resolution imaging reveals indirect coordination of opposite motors and a role for LIS1 in high-load axonal transport.

Yi JY, Ori-McKenney KM, McKenney RJ, Vershinin M, Gross SP, Vallee RB - J. Cell Biol. (2011)

Effect of LIS1 inhibition on lyso/LE transport in neurons. Control hippocampal and neocortical neurons exhibited rapid lysos/LEs mostly in the retrograde direction. LIS1 inhibition specifically and potently blocked movement of large lysos/LEs, especially at axonal bends and branch points, with little effect on the smaller vesicular transport. These effects were not observed in nonneuronal cells, which is consistent with a role for LIS1 in transport under higher resistance conditions. Red dots indicate lyso/LE particles. Blue arrows indicate transport directions.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3198168&req=5

fig5: Effect of LIS1 inhibition on lyso/LE transport in neurons. Control hippocampal and neocortical neurons exhibited rapid lysos/LEs mostly in the retrograde direction. LIS1 inhibition specifically and potently blocked movement of large lysos/LEs, especially at axonal bends and branch points, with little effect on the smaller vesicular transport. These effects were not observed in nonneuronal cells, which is consistent with a role for LIS1 in transport under higher resistance conditions. Red dots indicate lyso/LE particles. Blue arrows indicate transport directions.
Mentions: Together, our results support a requirement for LIS1 in high-load forms of dynein transport. We argue that the large lysos/LEs must be under LIS1 control even when traveling at high rates. This observation has the important consequence that LIS1 must be continuously active during high-speed stepping of dynein along the axonal microtubules. The nature of the resistance encountered by the larger lysos/LEs in our study is uncertain but likely involves local cytoplasmic constrictions, obstructions, or regions of higher viscosity (Figs. 3 B and 5). In this view, oscillations could reflect repeated efforts to bypass these impediments. The extent to which microtubule plus-end–directed kinesins contribute to these behaviors also remains to be explored further. Our results identify a novel conditional role for LIS1 in axonal transport. Mutations in cytoplasmic dynein, which affect vesicular transport, also result in neurodegeneration (Ori-McKenney et al., 2010). Whether similar effects will be found for the LIS1 gene remains an important issue for further investigation.

Bottom Line: The specific physiological roles of dynein regulatory factors remain poorly understood as a result of their functional complexity and the interdependence of dynein and kinesin motor activities.Acute dynein inhibition in nonneuronal cells caused an immediate dispersal of diverse forms of cargo, resulting from a sharp decrease in microtubule minus-end run length followed by a gradual decrease in plus-end runs.Our acute inhibition results argue against direct mechanical activation of opposite-directed motors and offer a novel approach of potential broad utility in the study of motor protein function in vivo.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pathology and Cell Biology, Columbia University, New York, NY 10027, USA.

ABSTRACT
The specific physiological roles of dynein regulatory factors remain poorly understood as a result of their functional complexity and the interdependence of dynein and kinesin motor activities. We used a novel approach to overcome these challenges, combining acute in vivo inhibition with automated high temporal and spatial resolution particle tracking. Acute dynein inhibition in nonneuronal cells caused an immediate dispersal of diverse forms of cargo, resulting from a sharp decrease in microtubule minus-end run length followed by a gradual decrease in plus-end runs. Acute LIS1 inhibition or LIS1 RNA interference had little effect on lysosomes/late endosomes but severely inhibited axonal transport of large, but not small, vesicular structures. Our acute inhibition results argue against direct mechanical activation of opposite-directed motors and offer a novel approach of potential broad utility in the study of motor protein function in vivo. Our data also reveal a specific but cell type-restricted role for LIS1 in large vesicular transport and provide the first quantitative support for a general role for LIS1 in high-load dynein functions.

Show MeSH
Related in: MedlinePlus