去磷酸化对Alzheimer神经原纤维缠结结构和功能的影响

Effect of Dephosphorylation on the Structure and Function of Alzheimer Neurofibrillary Tangles

探讨去磷酸化作用对Alzheimer神经原纤维缠结结构和功能的影响。结果发现,将蛋白磷酸酯酶—2A或—2B型与Alzheimer神经原纤维缠结在37℃保温45min可使缠结结构松解,神经原纤维缠结的基本单位双螺旋丝的螺旋性趋于消失;延长去磷酸化反应时间至3h可使缠结结构进一步松解,产生大量单个螺旋丝原纤维,并释放大量游离双螺旋丝片段和比对照组高约25％的游离tau蛋白;去磷酸化作用可不同程度恢复神经原纤维缠结中tau蛋白促微管组装的生物学功能。这从结构和功能双重角度证明了Alzbeimer病脑病理损伤的可逆转性,为Alzheimer病治疗的可能性提供了实验依据。

The negative stain electron microscopy revealed a dissociation of the neurofibrillary tangles af-ter incubation of PHF Ⅱ-tau with PP-2A or PP-2B at 37 C for 45 min. The PHF tangles were dissociated in-to individual PHF, and the twists in PHF started becoming less defined. Further dissociation of the PHF and the tangles was seen by 3h dephosphorylation either by PP-2A or by PP-2B. An increasing dissociation of the tangles into individual PHF and dissociation of PHF into straight subfilaments/protofiiaments were frequently seen in the 3 h dephosphorylated samples. Quantitation by radioimmuno-dot blots revealed a net release of approximately 25% of total tau from PHF following dephosphorylation by PP-2A. Dephosphorylation of PHF II -tau both by PP-2A and PP-2B restored differentially the biological activity of tau in promoting the in vitro assembly of microtubules. These observations demonstrate that PHF Ⅱ -tau is accessible to dephosphory-lation, which makes it dissociable and biologically active. Therefore, dephosphorylation might inhibit and re-verse the neurofibrillary degeneration in Alzheimer brain.