Scott C W, Vulliet P R, Caputo C B
Pharmacology Department, ICI Americas Inc., Wilmington, DE 19897-2500.
Brain Res. 1993 May 21;611(2):237-42. doi: 10.1016/0006-8993(93)90508-k.
Tau protein was evaluated as a substrate for a proline-directed protein kinase (p34cdc2/p58cyclin A) which recognizes the phosphorylation site motif X-Ser/Thr-Pro-X. The shortest human tau isoform, expressed as a recombinant protein, was phosphorylated to a stoichiometry of 2 mol phosphate/mol tau. Phosphoamino acid analysis revealed phosphorylation of both serine and threonine residues. Phosphorylation of recombinant tau resulted in a decreased ability to induce microtubule assembly but had no effect on the final extent of microtubule formation or on the rate of cold-induced microtubule disassembly. Phosphorylation of tau by the proline-directed protein kinase completely blocked immunoreactivity with antibody SMI33. Phosphorylation did not create the epitopes for the phosphate-dependent antibodies SMI31 or SMI34. Antibody SMI33 recognizes neurofibrillary tangles after treatment with alkaline phosphatase, suggesting that the proline-directed protein kinase may phosphorylate tau at sites that are phosphorylated in Alzheimer's disease.
tau蛋白被评估为脯氨酸定向蛋白激酶（p34cdc2/p58细胞周期蛋白A）的底物，该激酶识别磷酸化位点基序X-丝氨酸/苏氨酸-脯氨酸-X。最短的人类tau异构体以重组蛋白形式表达，其磷酸化化学计量比为2摩尔磷酸/摩尔tau。磷酸氨基酸分析显示丝氨酸和苏氨酸残基均发生了磷酸化。重组tau的磷酸化导致诱导微管组装的能力下降，但对微管形成的最终程度或冷诱导微管解聚的速率没有影响。脯氨酸定向蛋白激酶对tau的磷酸化完全阻断了与抗体SMI33的免疫反应性。磷酸化并未产生针对磷酸依赖性抗体SMI31或SMI34的表位。用碱性磷酸酶处理后，抗体SMI33可识别神经原纤维缠结，这表明脯氨酸定向蛋白激酶可能在阿尔茨海默病中发生磷酸化的位点使tau磷酸化。
