Differential activities, subcellular distribution and tissue expression patterns of three members of Slingshot family phosphatases that dephosphorylate cofilin
Differential activities, subcellular distribution and tissue expression patterns of three members of Slingshot family phosphatases that dephosphorylate cofilin
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DOI：
10.1046/j.1365-2443.2003.00678.x
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发表时间：
2003-10-01
期刊：
影响因子：
2.1
通讯作者：
Mizuno, K
中科院分区：
文献类型：
--
作者：
Ohta, Y;Kousaka, K;Mizuno, K
背景资料：Cofilin是肌动蛋白丝动力学的一个关键调节因子，它被LIM激酶在Ser-3位磷酸化而失活，并被Slingshot（SSH.Results）蛋白磷酸酶家族去磷酸化而重新激活。SSH-1 L和SSH-2L与肌动蛋白丝紧密结合并共定位，而SSH-3L则没有。当在培养细胞中表达时，SSH-1 L、SSH-2L和SSH-3L降低了细胞中Ser-3磷酸化cofilin（P-cofilin）的水平，并抑制了LIM激酶诱导的肌动蛋白重组，尽管SSH-3L的效果不如SSH-1 L和SSH-2L。在无细胞试验中，SSH-1 L和SSH-2L有效地去磷酸化P-cofilin，而SSH-3L这样做只是微弱的。使用SSH-1 L和SSH-2L的缺失突变体，我们发现N-末端和C-末端催化外区域分别对cofilin磷酸酶和F-肌动蛋白结合活性至关重要。原位杂交分析揭示了神经元和非神经元组织中每个小鼠Ssh基因表达的特征模式;特别是，Ssh-3在上皮组织中的表达是明显的。SSH-1 L、SSH-2L和SSH-3L具有去磷酸化P-cofilin的潜力，但亚细胞分布、F-肌动蛋白结合活性、特异性磷酸酶活性和表达模式显著不同，这表明它们在各种细胞和发育事件中具有相关但不同的功能。
Background: Cofilin, a key regulator of actin filament dynamics, is inactivated by phosphorylation at Ser-3 by LIM-kinases and is reactivated by dephosphorylation by a family of protein phosphatases, termed Slingshot (SSH).Results: We have identified two novel isoforms of SSHs, termed SSH-2L and SSH-3L and characterized them in comparison with SSH-1L that was previously reported. SSH-1L and SSH-2L, but not SSH-3L, tightly bound to and co-localized with actin filaments. When expressed in cultured cells, SSH-1L, SSH-2L and SSH-3L decreased the level of Ser-3-phosphorylated cofilin (P-cofilin) in cells and suppressed LIM-kinase-induced actin reorganization, although SSH-3L was less effective than SSH-1L and SSH-2L. In cell-free assays, SSH-1L and SSH-2L efficiently dephosphorylated P-cofilin, whereas SSH-3L did do so only weakly. Using deleted mutants of SSH-1L and SSH-2L, we found that the N-terminal and C-terminal extracatalytic regions are critical for cofilin-phosphatase and F-actin-binding activities, respectively. In situ hybridization analyses revealed characteristic patterns of expression of each of the mouse Ssh genes in both neuronal and non-neuronal tissues; in particular, expression of Ssh-3 in epithelial tissues is evident.Conclusion: SSH-1L, SSH-2L and SSH-3L have the potential to dephosphorylate P-cofilin, but subcellular distribution, F-actin-binding activity, specific phosphatase activity and expression patterns significantly differ, which suggests that they have related but distinct functions in various cellular and developmental events.