title: Combinatorial Tau pseudophosphorylation: markedly different regulatory effects on microtubule assembly and dynamic instability than the sum of the individual parts.
abstract: Tau is a multiply phosphorylated protein that is essential for the development and maintenance of the nervous system. Errors in Tau action are associated with Alzheimer disease and related dementias. A huge literature has led to the widely held notion that aberrant Tau hyperphosphorylation is central to these disorders. Unfortunately, our mechanistic understanding of the functional effects of combinatorial Tau phosphorylation remains minimal. Here, we generated four singly pseudophosphorylated Tau proteins (at Thr(231), Ser(262), Ser(396), and Ser(404)) and four doubly pseudophosphorylated Tau proteins using the same sites. Each Tau preparation was assayed for its abilities to promote microtubule assembly and to regulate microtubule dynamic instability in vitro. All four singly pseudophosphorylated Tau proteins exhibited loss-of-function effects. In marked contrast to the expectation that doubly pseudophosphorylated Tau would be less functional than either of its corresponding singly pseudophosphorylated forms, all of the doubly pseudophosphorylated Tau proteins possessed enhanced microtubule assembly activity and were more potent at regulating dynamic instability than their compromised singly pseudophosphorylated counterparts. Thus, the effects of multiple pseudophosphorylations were not simply the sum of the effects of the constituent single pseudophosphorylations; rather, they were generally opposite to the effects of singly pseudophosphorylated Tau. Further, despite being pseudophosphorylated at different sites, the four singly pseduophosphorylated Tau proteins often functioned similarly, as did the four doubly pseudophosphorylated proteins. These data lead us to reassess the conventional view of combinatorial phosphorylation in normal and pathological Tau action. They may also be relevant to the issue of combinatorial phosphorylation as a general regulatory mechanism.
authors.affiliation: Neuroscience Research Institute and Department of Molecular and Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA.
authors.forename: Erkan
authors.initials: E
authors.lastname: Kiris
authors.forename: Donovan
authors.initials: D
authors.lastname: Ventimiglia
authors.forename: Mehmet E
authors.initials: ME
authors.lastname: Sargin
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Gaylord
authors.forename: Alphan
authors.initials: A
authors.lastname: Altinok
authors.forename: Kenneth
authors.initials: K
authors.lastname: Rose
authors.forename: B S
authors.initials: BS
authors.lastname: Manjunath
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Jordan
authors.forename: Leslie
authors.initials: L
authors.lastname: Wilson
authors.forename: Stuart C
authors.initials: SC
authors.lastname: Feinstein
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D006801:Humans; D008870:Microtubules / Q000378:metabolism*; D008954:Models, Biological; D017239:Paclitaxel / Q000494:pharmacology; D010766:Phosphorylation; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D016875:tau Proteins / Q000737:chemistry*
chemical_list: D018076:DNA, Complementary; D020033:Protein Isoforms; D016875:tau Proteins; D017239:Paclitaxel