Abstract
Multiple neurodegenerative disorders are linked to aberrant phosphorylation of microtubule-associated proteins (MAPs). Protein phosphatase 2A (PP2A) is the major MAP phosphatase; however, little is known about its regulation at microtubules. alpha 4 binds the PP2A catalytic subunit (PP2Ac) and the microtubule-associated E3 ubiquitin ligase MID1, and through unknown mechanisms can both reduce and enhance PP2Ac stability. We show MID1-dependent monoubiquitination of alpha 4 triggers calpain-mediated cleavage and switches alpha 4's activity from protective to destructive, resulting in increased Tau phosphorylation. This regulatory mechanism appears important in MAP-dependent pathologies as levels of cleaved alpha 4 are decreased in Opitz syndrome and increased in Alzheimer disease, disorders characterized by MAP hypophosphorylation and hyperphosphorylation, respectively. These findings indicate that regulated inter-domain cleavage controls the dual functions of alpha 4, and dysregulation of alpha 4 cleavage may contribute to Opitz syndrome and Alzheimer disease.
Original language | English |
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Pages (from-to) | 24207-24215 |
Number of pages | 9 |
Journal | Journal of Biological Chemistry |
Volume | 287 |
Issue number | 29 |
DOIs | |
Publication status | Published - 13 Jul 2012 |