Characterization of STEF, a guanine nucleotide exchange factor for Rac1, required for neurite growth
Characterization of STEF, a guanine nucleotide exchange factor for Rac1, required for neurite growth
复制标题
DOI：
10.1074/jbc.m106186200
复制
发表时间：
2002-01-25
影响因子：
4.8
通讯作者：
Nabeshima, Y
中科院分区：
文献类型：
--
作者：
Matsuo, N;Hoshino, M;Nabeshima, Y
越来越多的证据表明Rho家族GTP酶在神经系统的组织中起着关键作用。我们先前鉴定了Rac 1的鸟嘌呤核苷酸交换因子，STEF（SIF和Tiam 1-like exchange factor），其可以在KB细胞中诱导皱褶膜，并且在发育期间主要在脑中表达。在这里，我们的特点的分子本质的STEF和参与神经突生长。缺失分析揭示了不同的作用，为个别领域：PHnTSS膜协会，DH的酶活性，和PHc促进催化活性。STEF在N1 E-115神经母细胞瘤细胞中的异位表达以Rac 1依赖的方式诱导含有F-肌动蛋白、β III微管蛋白、MAP 2和GAP 43的神经突样过程，即使在含血清的神经突抑制条件下也是如此。我们进一步发现，PHnTSS STEF片段特异性抑制STEF和Tiam 1（一种密切相关的Rac 1鸟嘌呤核苷酸交换因子）的功能。内源性STEF和Tiam 1活性的抑制在N1 E-115细胞异位表达PHnTSS STEF导致抑制神经突生长在血清饥饿的条件下，这通常会诱导神经突形成。此外，这些抑制作用被外源性表达的STEF或Tiam 1所拯救，这表明STEF和Tiam 1通过激活Rac 1和发育过程中神经元细胞的连续细胞骨架重组参与神经突形成。
Accumulating evidence suggests that Rho family GTPases play critical roles in the organization of the nervous system. We previously identified a guanine nucleotide exchange factor of Rac1, STEF (SIF and Tiam 1-like exchange factor), which can induce ruffling membrane in KB cells and is predominantly expressed in the brain during development. Here, we characterize the molecular nature of STEF and its involvement in neurite growth. Deletion analyses revealed distinct roles for individual domains: PHnTSS for membrane association, DH for enzymatic activity, and PHc for promoting catalytic activity. Ectopic expression of STEF in N1E-115 neuroblastoma cells induced neurite-like processes containing F-actin, betaIII tubulin, MAP2, and GAP43 in a Rac1-dependent manner even under the serum-containing neurite-inhibiting conditions. We further found that a PHnTSS STEF fragment specifically inhibited the function of both STEF and Tiam1, a closely related Rac1 guanine nucleotide exchange factor. Suppression of endogenous STEF and Tiam1 activities in N1E-115 cells by ectopically expressed PHnTSS STEF resulted in inhibition of neurite outgrowth in serum-starved conditions, which usually induce neurite formation. Furthermore, these inhibitory effects were rescued by exogenously expressed STEF or Tiam1, suggesting that STEF and Tiam1 are involved in neurite formation through the activation of Rac1 and successive cytoskeletal reorganization of neuronal cells during development.