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Differential effect of three-repeat and four-repeat tau on mitochondrial axonal transport.

ABSTRACT: Tau protein is present in six different splice forms in the human brain and interacts with microtubules via either 3 or 4 microtubule binding repeats. An increased ratio of 3 repeat to 4 repeat isoforms is associated with neurodegeneration in inherited forms of frontotemporal dementia. Tau over-expression diminishes axonal transport in several systems, but differential effects of 3 repeat and 4 repeat isoforms have not been studied. We examined the effects of tau on mitochondrial transport and found that both 3 repeat and 4 repeat tau change normal mitochondrial distribution within the cell body and reduce mitochondrial localization to axons; 4 repeat tau has a greater effect than 3 repeat tau. Further, we observed that the 3 repeat and 4 repeat tau cause different alterations in retrograde and anterograde transport dynamics with 3 repeat tau having a slightly stronger effect on axon transport dynamics. Our results indicate that tau-induced changes in axonal transport may be an underlying theme in neurodegenerative diseases associated with isoform specific changes in tau's interaction with microtubules.

SUBMITTER: Stoothoff W

PROVIDER: S-EPMC2831412 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature

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Differential effect of three-repeat and four-repeat tau on mitochondrial axonal transport.

Stoothoff Will W Jones Phillip B PB Spires-Jones Tara L TL Joyner Daniel D Chhabra Ekta E Bercury Kathryn K Fan Zhanyun Z Xie Hong H Bacskai Brian B Edd Jon J Irimia Daniel D Hyman Bradley T BT

Journal of neurochemistry 20090803 2

Tau protein is present in six different splice forms in the human brain and interacts with microtubules via either 3 or 4 microtubule binding repeats. An increased ratio of 3 repeat to 4 repeat isoforms is associated with neurodegeneration in inherited forms of frontotemporal dementia. Tau over-expression diminishes axonal transport in several systems, but differential effects of 3 repeat and 4 repeat isoforms have not been studied. We examined the effects of tau on mitochondrial transport and f ...[more]

PMID: 19686388

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Project description:UNLABELLED:Despite the demonstration that amyloid-? (A?) can trigger increased tau phosphorylation and neurofibrillary tangle (NFT) formation in vivo, the molecular link associating A? and tau pathologies remains ill defined. Here, we observed that exposure of cultured primary neurons to A? trimers isolated from brain tissue of subjects with Alzheimer's disease led to a specific conformational change of tau detected by the antibody Alz50. A similar association was supported by postmortem human brain analyses. To study the role of A? trimers in vivo, we created a novel bigenic Tg-A?+Tau mouse line by crossing Tg2576 (Tg-A?) and rTg4510 (Tg-Tau) mice. Before neurodegeneration and amyloidosis, apparent A? trimers were increased by ?2-fold in 3-month-old Tg-A? and Tg-A?+Tau mice compared with younger mice, whereas soluble monomeric A? levels were unchanged. Under these conditions, the expression of soluble Alz50-tau conformers rose by ?2.2-fold in the forebrains of Tg-A?+Tau mice compared with nontransgenic littermates. In parallel, APP accumulated intracellularly, suggestive of a putative dysfunction of anterograde axonal transport. We found that the protein abundance of the kinesin-1 light chain (KLC1) was reduced selectively in vivo and in vitro when soluble A? trimers/Alz50-tau were present. Importantly, the reduction in KLC1 was prevented by the intraneuronal delivery of Alz50 antibodies. Collectively, our findings reveal that specific soluble conformers of A? and tau cooperatively disrupt axonal transport independently from plaques and tangles. Finally, these results suggest that not all endogenous A? oligomers trigger the same deleterious changes and that the role of each assembly should be considered separately. SIGNIFICANCE STATEMENT:The mechanistic link between amyloid-? (A?) and tau, the two major proteins composing the neuropathological lesions detected in brain tissue of Alzheimer's disease subjects, remains unclear. Here, we report that the trimeric A? species induce a pathological modification of tau in cultured neurons and in bigenic mice expressing A? and human tau. This linkage was also observed in postmortem brain tissue from subjects with mild cognitive impairment, when A? trimers are abundant. Further, this modification of tau was associated with the intracellular accumulation of the precursor protein of A?, APP, as a result of the selective decrease in kinesin light chain 1 expression. Our findings suggest that A? trimers might cause axonal transport deficits in AD.

Dataset Information

Differential effect of three-repeat and four-repeat tau on mitochondrial axonal transport.

Publications

Differential effect of three-repeat and four-repeat tau on mitochondrial axonal transport.

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