Interaction of tau with the neural membrane cortex is regulated by phosphorylation at sites that are modified in paired helical filaments.
The axonal microtubule-associated phosphoprotein tau interacts with neural plasma membrane (PM) components during neuronal development (Brandt, R., Léger, J., and Lee, G. (1995) J. Cell Biol. 131, 1327-1340). To analyze the mechanism and potential regulation of tau's PM association, a method was developed to isolate PM-associated tau using microsphere separation of surface-biotinylated cells. We show that tau's PM association requires an intact membrane cortex and that PM-associated tau and cytosolic tau are differentially phosphorylated at sites detected by several Alzheimer's disease (AD) diagnostic antibodies (Ser(199)/Ser(202), Thr(231), and Ser(396)/Ser(404)). In polar neurons, the association of endogenous tau phosphoisoforms with the membrane cortex correlates with an enrichment in the axonal compartment. To test for a direct effect of AD-specific tau modifications in determining tau's interactions, a phosphomutant that simulates an AD-like hyperphosphorylation of tau was produced by site-directed mutagenesis of Ser/Thr residues to negatively charged amino acids (Glu). These mutations completely abolish tau's association with the membrane cortex; however, the construct retains its capability to bind to microtubules. The data suggest that a loss of tau's association with the membrane cortex as a result of phosphorylation at sites that are modified during disease contributes to somatodendritic tau accumulation, axonal microtubule disintegration, and neuronal death characteristic for AD.
Maas
T
T
Department of Neurobiology, Interdisziplinäres Zentrum für Neurowissenschaften (IZN), University of Heidelberg, Im Neuenheimer Feld 364, D-69120 Heidelberg, Germany.
Eidenmüller
J
J
Brandt
R
R
D000199:Actins / Q000378:metabolism; D000544:Alzheimer Disease / Q000276:immunology / Q000378:metabolism; D000818:Animals; D019921:Biotinylation; D002462:Cell Membrane / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008863:Microspheres; D008870:Microtubules / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009474:Neurons; D019319:Okadaic Acid / Q000494:pharmacology; D016716:PC12 Cells; D010766:Phosphorylation; D011485:Protein Binding; D051381:Rats; D014162:Transfection; D016875:tau Proteins / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D016875:tau Proteins; D019319:Okadaic Acid