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1 July 2004 Attenuation of okadaic acid–induced hyperphosphorylation of cytoskeletal proteins by heat preconditioning and its possible underlying mechanisms
Ya Fei Xu, Yong Jie Zhang, Ai Hong Zhang, Qi Zhang, Tangchun Wu, Jian-Zhi Wang
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Abstract

An imbalanced phosphorylation system is recognized to be one of the main reasons for Alzheimer-like hyperphosphorylation of cytoskeletal proteins. However, little is known about the strategies rectifying the lesions caused by this disrupted phosphorylation. To search for the means to arrest Alzheimer-like damages and explore the underlying mechanisms, in this study we treated N2a/peuht40 cells with okadaic acid (OA), a specific inhibitor of protein phosphatase-2A (PP-2A) and PP-1, to mimic an Alzheimer-like phosphatase-deficient system and then used heat preconditioning (42°C for 1 hour) to induce the expression of inducible heat shock protein 70 (Hsp70) in the cells. We observed that heat preconditioning arrested OA-induced hyperphosphorylation of neurofilament (NF) protein at SMI34 and SMI33 epitopes as well as hyperphosphorylation of tau at Tau-1 and PHF-1 epitopes. It counteracted OA-induced decrease in PP-2A activity with a concurrent inhibition in constitutive activity of mitogen-activated protein kinases (MAPKs) and cyclic adenosine 5′-monophosphate–dependent protein kinase A (PKA). Conversely, quercetin, a recognized blocker of stress-responsive Hsp70 expression, diminished the effects caused by heat preconditioning. These results suggested that Hsp70 antagonized OA-induced Alzheimer-like NF and tau hyperphosphorylation, and the restoration of PP-2A and inhibition of MAPKs-PKA activity might be part of the underlying mechanisms for the rectification of OA-induced hyperphosphorylation.

Ya Fei Xu, Yong Jie Zhang, Ai Hong Zhang, Qi Zhang, Tangchun Wu, and Jian-Zhi Wang "Attenuation of okadaic acid–induced hyperphosphorylation of cytoskeletal proteins by heat preconditioning and its possible underlying mechanisms," Cell Stress & Chaperones 9(3), 304-312, (1 July 2004). https://doi.org/10.1379/CSC-23R1.1
Received: 12 February 2004; Accepted: 1 June 2004; Published: 1 July 2004
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