Attenuation of okadaic acid-induced hyperphosphorylation of cytoskeletal proteins by heat preconditioning and its possible underlying mechanisms.
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 degrees 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.
Xu
Ya Fei
YF
Pathophysiology Department, Neuroscience Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China.
Zhang
Yong Jie
YJ
Zhang
Ai Hong
AH
Zhang
Qi
Q
Wu
Tangchun
T
Wang
Jian-Zhi
JZ
D000544:Alzheimer Disease / Q000378:metabolism / Q000503:physiopathology; D000911:Antibodies, Monoclonal / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D018869:Heat-Shock Response / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D016900:Neurofilament Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2; D011794:Quercetin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D016875:tau Proteins / Q000378:metabolism
D000911:Antibodies, Monoclonal; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D018840:HSP70 Heat-Shock Proteins; D016900:Neurofilament Proteins; C085349:PHF-1 monoclonal antibody; D016875:tau Proteins; D019319:Okadaic Acid; D011794:Quercetin; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2