OGlcNAcylation and phosphorylation have opposing structural effects in tau: phosphothreonine induces particular conformational order.
OGlcNAcylation and phosphorylation have opposing structural effects in tau: phosphothreonine induces particular conformational order.
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DOI：
10.1021/ja407156m
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发表时间：
2014-03-12
影响因子：
15
通讯作者：
Zondlo NJ
中科院分区：
文献类型：
--
作者：
Brister MA;Pandey AK;Bielska AA;Zondlo NJ
磷酸化和OGlcNAc化是动态的细胞内蛋白质翻译后修饰，其经常在相同的丝氨酸和苏氨酸残基上交替观察到。磷酸化和OGlcNAc化通常发生在蛋白质的天然无序区域，并且通常具有相反的功能效应。在微管相关蛋白tau中，过度磷酸化与蛋白质错误折叠和聚集相关，如阿尔茨海默病的神经元缠结，而OGlcNAc化稳定了tau的可溶形式。合成了一系列衍生自tau的富含脯氨酸的结构域（残基174-251）的肽，其具有游离Ser/Thr羟基、磷酸化Ser/Thr（pSer/pThr）、OGlcNAc酰化Ser/Thr和二乙基磷酸化Ser/Thr。通过CD和NMR发现磷酸化和OGlcNAc化对聚脯氨酸螺旋（PPII）形成具有相反的结构效应，其中磷酸化有利于PPII，OGlcNAc化反对PPII，以及结构中的游离羟基中间体，并且磷酸化结构效应大于OGlcNAc化。对于tau 196 -209，磷酸化和OGlcNAc化具有相似的结构效应，与新生α-螺旋相反。Phosphomimic Glu表现出PPII的结构效应。由于Thr磷酸化引起的结构变化大于Ser磷酸化或Glu引起的结构变化，由于二价阴离子的特殊构象限制，平均3 J αN = 3.5 Hz（pThr）与5.4 Hz（pSer），而Thr、Ser和Glu分别为7.2、6.8和6.2 Hz，这些值与主链扭转角θ相关。双阴离子磷酸苏氨酸诱导强的磷酸苏氨酸酰胺保护和低场酰胺化学位移（δ平均值= 9.63 ppm），与稳定的磷酸-酰胺氢键的形成一致。这些数据表明，由于更大的诱导结构效应，苏氨酸磷酸化可能比丝氨酸磷酸化具有更大的结构重要性。
Phosphorylation and OGlcNAcylation are dynamic intracellular protein post-translational modifications that frequently are alternatively observed on the same serine and threonine residues. Phosphorylation and OGlcNAcylation commonly occur in natively disordered regions of proteins, and often have opposing functional effects. In the microtubule-associated protein tau, hyperphosphorylation is associated with protein misfolding and aggregation as the neurofibrillary tangles of Alzheimer’s disease, whereas OGlcNAcylation stabilizes the soluble form of tau. A series of peptides derived from the proline-rich domain (residues 174–251) of tau was synthesized, with free Ser/Thr hydroxyls, phosphorylated Ser/Thr (pSer/pThr), OGlcNAcylated Ser/Thr, and diethylphosphorylated Ser/Thr. Phosphorylation and OGlcNAcylation were found by CD and NMR to have opposing structural effects on polyproline helix (PPII) formation, with phosphorylation favoring PPII, OGlcNAcylation opposing PPII, and the free hydroxyls intermediate in structure, and with phosphorylation structural effects greater than OGlcNAcylation. For tau196–209, phosphorylation and OGlcNAcylation had similar structural effects, opposing a nascent α-helix. Phosphomimic Glu exhibited PPII-favoring structural effects. Structural changes due to Thr phosphorylation were greater than those of Ser phosphorylation or Glu, with particular conformational restriction as the dianion, with mean 3JαN = 3.5 Hz (pThr) versus 5.4 Hz (pSer), compared to 7.2, 6.8, and 6.2 Hz for Thr, Ser, and Glu, respectively, values that correlate with the backbone torsion angle ϕ. Dianionic phosphothreonine induced strong phosphothreonine amide protection and downfield amide chemical shifts (δmean = 9.63 ppm), consistent with formation of a stable phosphate-amide hydrogen bond. These data suggest potentially greater structural importance of threonine phosphorylation than serine phosphorylation due to larger induced structural effects.
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