Dynamics of epithelial cells and neurons through regulation of dephosphorylation and reactivation of cofilin

Cofilin是肌动蛋白丝动力学的关键调节因子，可通过lim激酶的Ser-3磷酸化而失活，并通过称为Slingshot （SSH）的蛋白磷酸酶家族的去磷酸化而重新激活。人类或小鼠基因组有三个拷贝的Ssh基因（Ssh1-Ssh3）。先前的原位杂交分析揭示了每个小鼠ssh基因在神经元和非神经元组织中的表达特征模式。我们研究了单个基因产物的内源性表达水平，结果表明，sh-2和sh-3分别在神经组织和上皮组织中高表达。为了探索sh-3在上皮组织中的作用，我们分离了MDCK细胞的衍生物，其中sh-3可以在加入强力霉素后被敲除。由于我们在MDCK细胞中检测到Ssh-1，我们进一步分离了Ssh-1和Ssh-3都被敲低的亚系，并一直在研究细胞形状的表型。为了研究体内sh-3在上皮细胞形态发生中的作用，我们制造了敲除sh-3的小鼠。sh-3敲除小鼠在两种不同的背景下都是可存活和可生育的，我们一直在寻找各种上皮组织的表型，如乳腺和肾脏。

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). The human or mouse genome has three copies of Ssh genes (Ssh1-Ssh3). Previous in situ hybridization analyses revealed characteristic patterns of expression of each of the mouse ssh genes in both neuronal and non-neuronal tissues. Here we studied levels of endogenous expression of individual gene products and showed that expression of Ssh-2 and that of Ssh-3 are high in neural and epithelial tissues, respectively. To explore roles of Ssh-3 in epithelial tissues, we isolated derivatives of MDCK cells in which Ssh-3 can be knocked down upon addition of doxycycline. Because we detected Ssh-1 in MDCK cells, we further isolated sublines in which both Ssh-1 and Ssh-3 are knocked down and have been studying phenotypes of cell shape. To examine in vivo roles of Ssh-3 in epithelial morphogenesis, we generated Ssh-3-knock out mice. The Ssh-3-knock out mice are viable and fertile in two different backgrounds and we have been hunting for phenotypes of various epithelial tissues, such as mammary glands and kidney.