Glycogen synthase kinase 3β phosphorylates tau at both primed and unprimed sites -: Differential impact on microtubule binding
Glycogen synthase kinase 3β phosphorylates tau at both primed and unprimed sites -: Differential impact on microtubule binding
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DOI：
10.1074/jbc.m206236200
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发表时间：
2003-01-03
影响因子：
4.8
通讯作者：
Johnson, GVW
中科院分区：
文献类型：
--
作者：
Cho, JH;Johnson, GVW
糖原合酶激酶3β（GSK3β）在起始（primed）和非起始（unprimed）表位对底物进行磷酸化，包括微管相关蛋白tau。GSK3β对tau的磷酸化负向调节tau - 微管相互作用；然而，在起始和非起始表位的磷酸化对tau的不同影响尚不清楚。为了检测在起始和非起始表位tau的磷酸化以及这如何影响tau的功能，使用了GSK3β的R96A突变体，该突变可阻止在起始位点对底物的磷酸化。GSK3β和GSK3β - R96A在原位均能有效地使tau磷酸化。然而，与GSK3β相比，GSK3β - R96A的表达导致tau在起始位点的磷酸化显著减少。相反，GSK3β - R96A对非起始tau位点的磷酸化程度显著高于GSK3β。用cdk5/p25对tau进行预磷酸化会削弱GSK3β - R96A使tau磷酸化的能力，而GSK3β - R96A对重组tau的磷酸化程度显著高于GSK3β。此外，GSK3β的过表达会减少与微管相关的tau的量，但仅当tau在起始位点被磷酸化时才会如此，因为GSK3β - R96A对tau的磷酸化不会负向调节tau与微管的关联。这些结果表明，GSK3β介导的tau在起始位点的磷酸化在调节tau与微管的相互作用方面比在非起始表位的磷酸化起着更重要的作用。
Glycogen synthase kinase 3beta (GSK3beta) phosphorylates substrates, including the microtubule-associated protein tau, at both primed and unprimed epitopes. GSK3beta phosphorylation of tau negatively regulates tau-microtubule interactions; however the differential effects of phosphorylation at primed and unprimed epitopes on tau is unknown. To examine the phosphorylation of tau at primed and unprimed epitopes and how this impacts tau function, the R96A mutant of GSK3beta was used, a mutation that prevents phosphorylation of substrates at primed sites. Both GSK3beta and GSK3beta-R96A phosphorylated tau efficiently in situ. However, expression of GSK3beta-R96A resulted in significantly less phosphorylation of tau at primed sites compared with GSK3beta. Conversely, GSK3beta-R96A phosphorylated unprimed tau sites to a significantly greater extent than GSK3beta. Pre-phosphorylating tau with cdk5/p25 impaired the ability of GSK3beta-1196A to phosphorylate tau, whereas GSK3beta-R96A phosphorylated recombinant tau to a significantly greater extent than GSK3beta. Moreover, the amount of tau associated with microtubules was reduced by overexpression of GSK3beta but only when tau was phosphorylated at primed sites, as phosphorylation of tau by GSK3beta-R96A did not negatively regulate the association of tau with microtubules. These results demonstrate that GSK3beta-mediated phosphorylation of tau at primed sites plays a more significant role in regulating the interaction of tau with microtubules than phosphorylation at unprimed epitopes.