Dataset Information

Tau phosphorylation affects its axonal transport and degradation.

ABSTRACT: Phosphorylated forms of microtubule-associated protein tau accumulate in neurofibrillary tangles in Alzheimer's disease. To investigate the effects of specific phosphorylated tau residues on its function, wild type or phosphomutant tau was expressed in cells. Elevated tau phosphorylation decreased its microtubule binding and bundling, and increased the number of motile tau particles, without affecting axonal transport kinetics. In contrast, reducing tau phosphorylation enhanced the amount of tau bound to microtubules and inhibited axonal transport of tau. To determine whether differential tau clearance is responsible for the increase in phosphomimic tau, we inhibited autophagy in neurons which resulted in a 3-fold accumulation of phosphomimic tau compared with wild type tau, and endogenous tau was unaffected. In autophagy-deficient mouse embryonic fibroblasts, but not in neurons, proteasomal degradation of phosphomutant tau was also reduced compared with wild type tau. Therefore, autophagic and proteasomal pathways are involved in tau degradation, with autophagy appearing to be the primary route for clearing phosphorylated tau in neurons. Defective autophagy might contribute to the accumulaton of tau in neurodegenerative diseases.

SUBMITTER: Rodriguez-Martin T

PROVIDER: S-EPMC3684773 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Tau phosphorylation affects its axonal transport and degradation.

Rodríguez-Martín Teresa T Cuchillo-Ibáñez Inmaculada I Noble Wendy W Nyenya Fanon F Anderton Brian H BH Hanger Diane P DP

Neurobiology of aging 20130417 9

Phosphorylated forms of microtubule-associated protein tau accumulate in neurofibrillary tangles in Alzheimer's disease. To investigate the effects of specific phosphorylated tau residues on its function, wild type or phosphomutant tau was expressed in cells. Elevated tau phosphorylation decreased its microtubule binding and bundling, and increased the number of motile tau particles, without affecting axonal transport kinetics. In contrast, reducing tau phosphorylation enhanced the amount of tau ...[more]

PMID: 23601672

Similar Datasets

Project description:Introduction: Tau is a microtubule associated phosphoprotein found principally in neurons. Prevailing dogma continues to define microtubule stabilization as the major function of tau in vivo, despite several lines of evidence suggesting this is not the case. Most importantly, tau null mice have deficits in axonal outgrowth and neuronal migration while still possessing an extensive microtubule network. Instead, mounting evidence suggests that tau may have a major function in the regulation of fast axonal transport (FAT) through activation of neuronal signaling pathways. Previous studies identified a phosphatase activating domain (PAD) at the tau N-terminal that is normally sequestered, but is constitutively exposed in tauopathies. When exposed, the PAD activates a signaling cascade involving PP1 and GSK3β which affects cellular functions including release of cargo from kinesin. Furthermore, we discovered that PAD exposure can be regulated by a single phosphorylation at T205. Exposure of the PAD is an early event in multiple tauopathies and a major contributing factor to neurodegeneration associated with tau hyperphosphorylation. However, effects of tau PAD exposure on anterograde FAT raised the interesting possibility that this pathway may be a mechanism for physiological regulation of cargo delivery through site-specific phosphorylation of tau and transient activation of PP1 and GSK3β. Significantly, there is already evidence of local control of PP1 and GSK3β at sites which require cargo delivery. Methods: To investigate this hypothesis, first we evaluated cellular localization of tau PAD exposure, pT205 tau phosphorylation, and active GSK3β in primary hippocampal neurons during development. Second, we analyzed the axonal outgrowth of tau knockout neurons following transfection with full length hTau40-WT, hTau40-ΔPAD, or hTau40-T205A. Results and Discussion: The results presented here suggest that transient activation of a PP1-GSK3β signaling pathway through locally regulated PAD exposure is a mechanism for cargo delivery, and thereby important for neurite outgrowth of developing neurons.

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

Tau phosphorylation affects its axonal transport and degradation.

Publications

Tau phosphorylation affects its axonal transport and degradation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets