Role of Ser50 phosphorylation in SCG10 regulation of microtubule depolymerization
Role of Ser50 phosphorylation in SCG10 regulation of microtubule depolymerization
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DOI：
10.1002/jnr.20462
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发表时间：
2005-05
影响因子：
4.2
通讯作者：
T. Togano;M. Kurachi;Michitoshi Watanabe;G. Grenningloh;M. Igarashi
中科院分区：
文献类型：
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作者：
T. Togano;M. Kurachi;Michitoshi Watanabe;G. Grenningloh;M. Igarashi
Stathmin样蛋白家族的成员可降解微管（MT），可能是由于每个Stathmin单体能够结合复合物（T2 S复合物）中的两个微管蛋白异源二聚体。SCG 10是该家族的成员，定位于神经元的生长锥中。它有四个丝氨酸磷酸化位点（S50，S63，S73和S97）。其中，S50和S97被cAMP依赖性蛋白激酶磷酸化，这是一种参与生长锥引导的酶。当stathmins中的等同位点被磷酸化时，它们失去了去磷酸化MT的能力。我们研究了SCG 10中两个cAMP依赖性蛋白激酶（PKA）磷酸化位点的具体作用。仅在S50上磷酸化的SCG 10突变体保留了MT解聚的能力，但在S97上或在S50和S97上磷酸化的SCG 10失去了MT解聚活性。表面等离子体共振研究表明，磷酸化的SCG 10在这些网站减少了微管蛋白异源二聚体结合，主要是由于降低的关联率。特别是，与其他两种磷酸化形式相比，在S50磷酸化的SCG 10具有显著较小的第一微管蛋白异二聚体结合的解离常数和较大的第二异二聚体结合的缔合和解离速率常数。这表明S50的磷酸化通过调节T2 S复合物的形成来补偿在其他位点的磷酸化的影响。此外，这些结果表明，S50-P保持MT解聚活性，这表明S50和S97磷酸化的生物学功能不同。© 2005 Wiley利斯公司
Members of the stathmin‐like protein family depolymerize microtubules (MTs), probably due to the ability of each stathmin monomer to bind two tubulin heterodimers in a complex (T2S complex). SCG10, a member of this family, is localized in the growth cone of neurons. It has four identified sites of serine phosphorylation (S50, S63, S73, and S97). Of these, S50 and S97 are phosphorylated by cAMP‐dependent protein kinase, an enzyme involved in growth cone guidance. When the equivalent sites in stathmins are phosphorylated, they lose their ability to depolymerize MTs. We investigated the specific role of the two cAMP‐dependent protein kinase (PKA) phosphorylation sites in SCG10. A mutant of SCG10 phosphorylated only on S50 retained the ability to depolymerize MTs, but SCG10 phosphorylated on S97 or on both S50 and S97 lost MT‐depolymerizing activity. Surface plasmon resonance studies revealed that the phosphorylation of SCG10 at these sites reduced the tubulin heterodimer binding, mainly due to a reduced rate of association. In particular, compared to the two other phosphorylated forms, SCG10 phosphorylated at S50 had a significantly smaller dissociation constant for the binding of the first tubulin heterodimer and larger association and dissociation rate constants for the binding of the second heterodimer. This indicates that the phosphorylation of S50 compensates for the effect of phosphorylation at other sites by modulating T2S complex formation. Furthermore, these results suggest that S50‐P maintains MT‐depolymerizing activity, which indicates that the biological functions of phosphorylation at S50 and S97 are different. © 2005 Wiley‐Liss, Inc.