Glycogen synthase kinase-3beta and the p25 activator of cyclin dependent kinase 5 increase pausing of mitochondria in neurons.
The complex bi-directional axoplasmic transport of mitochondria is essential for proper metabolic functioning of neurons and is controlled by phosphorylation. We have investigated by time-lapse imaging the effects of increased expression of glycogen synthase kinase-3beta (GSK-3beta) and of the p25 activator of cyclin dependent kinase 5 on mitochondria movements in mammalian cortical neurons and in PC12 cells. Both GSK-3beta and p25 increased the stationary behaviour of mitochondria in PC12 and in neurons, decreased their anterograde transport but did not affect the intrinsic velocities of mitochondria. The microtubule-associated tau proteins were more phosphorylated in GSK-3beta and p25 transfected neurons, but ultrastructural observation showed that these cells still contained microtubules and nocodazole treatment further reduced residual mitochondria movements in GSK-3beta or p25 transfected neurons, indicating that microtubule disruption was not the primary cause of increased mitochondrial stationary behaviour in GSK-3beta or p25 transfected neurons. Our results suggest that increased expression of GSK-3beta and p25 acted rather by decreasing the frequency of mitochondrial movements driven by molecular motors and that GSK-3beta and p25 might regulate these transports by controlling the time that mitochondria spend pausing, rather than their velocities.
Morel
M
M
Laboratory of Histology, Neuroanatomy and Neuropathology, Université Libre de Bruxelles, 808 route de Lennik, B-1070 Brussels, Belgium.
Authelet
M
M
Dedecker
R
R
Brion
J P
JP
D000818:Animals; D002470:Cell Survival; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta; D049452:Green Fluorescent Proteins / Q000235:genetics; D007700:Kinetics; D051379:Mice; D008870:Microtubules / Q000648:ultrastructure; D008928:Mitochondria / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009474:Neurons / Q000502:physiology* / Q000648:ultrastructure; D016716:PC12 Cells; D010766:Phosphorylation; D051381:Rats; D014162:Transfection; D016875:tau Proteins / Q000378:metabolism
D009419:Nerve Tissue Proteins; C485184:enhanced green fluorescent protein; C089495:neuronal Cdk5 activator (p25-p35); D016875:tau Proteins; D049452:Green Fluorescent Proteins; D051360:Cyclin-Dependent Kinase 5; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3