Elsevier

Neuroscience

Volume 61, Issue 4, August 1994, Pages 765-772
Neuroscience

Dephosphorylation of Alzheimer's disease abnormally phosphorylated tau by protein phosphatase-2A

https://doi.org/10.1016/0306-4522(94)90400-6Get rights and content

Abstract

Microtubule-associated protein tau is abnormally hyperphosphorylated in the brain of patients with Alzheimer's disease, and is the major protein subunit of paired helical filaments. There is also a significant pool of non-paired helical filament abnormally phosphorylated tau in Alzheimer's disease brain. In the present study, the site-specific dephosphorylation of this Alzheimer's disease abnormally phosphorylated tau by protein phosphatase-2A was studied and compared with that by protein phosphatase-2B. The dephosphorylation was detected by its interaction with several phosphorylation-dependent antibodies to various abnormal phosphorylation sites. Protein phosphatase-2A was able to dephosphorylate the abnormally phosphorylated tau at Ser-46, Ser-199, Ser-202, Ser-396 and Ser-404, but not at Ser-235 (the amino acids are numbered according to the largest isoform of human tau, tau441). Two major types of protein phosphatase-2A, protein phosphatase-2A1 and -2A2, dephosphorylated the abnormally phosphorylated tau at approximately the same rate. After the abnormally phosphorylated tau was dephosphorylated by protein phosphatase-2A, its relative mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis increased. The dephosphorylation of the abnormal tau by protein phosphatase-2A1 and -2A2 was markedly stimulated by Mn2+.

These results suggest that tau dephosphorylation is catalysed by protein phosphatase-2A in addition to protein phosphatase-2B. A deficiency of either protein phosphatase-2A or -2B, or both, may be involved in abnormal phosphorylation of tau in Alzheimer's disease.

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