Functions of cofilin, an actin-regulating protein

1)对传统的肌动蛋白荧光标记方法进行了改进，证明了Cofilin能切断肌动蛋白细丝并加速其尖端单体的释放。在亚化学计量条件下，0.8μM Cofilin在每270个单体亚基中切割约2.2μM的丝状肌动蛋白，并在pH 7.1时使解聚速率提高5.7倍。在多头绒泡菌中，一种热应激诱导的cist特异性肌动蛋白结合蛋白被鉴定为Aip1。Aip1对肌动蛋白细丝的切断和解聚均有促进作用。3)我们在盘状螺旋藻中发现了一种新型的cofilin家族成员cofilin-2。Cofilin-2由143个氨基酸残基组成。Cofilin-2与COF…有显著的同源性(30.6%同源性)在其整个序列中有更多的ILIN-1，但不保留一些在Cofilin家族成员中保守的残基，表明Cofilin-2属于一种新型的Cofilin家族。纯化的cofilin-2以剂量和pH依赖的方式解聚肌动蛋白细丝，但不与肌动蛋白细丝共生，而cofilin-1与肌动蛋白细丝共聚合。Cofilin-2在营养细胞中不表达，在发育的聚集阶段，cofilin-2的表达减少。4)我们研究了Lim-kins1，一种磷酸化肌动蛋白解聚蛋白cofilin的蛋白，在信号素3A诱导的生长锥体崩溃中的作用。我们发现信号素3A依次诱导生长锥体上的粘附素的磷酸化和去磷酸化。一种合成的含有cofilin磷酸化位点的细胞通透性多肽在体外和体内抑制LIM-Kinase，基本上抑制了信号素3A诱导的生长锥体翻转。这些数据表明，LIM-Kinase对cofilin的磷酸化是信号素3A引起的视锥细胞塌陷的关键信号事件。较少

1) We improved the conventional method using fluorescently labeled actin, then demonstrated that cofilin severs actin filaments and accelerates monomer release at their pointed ends. Under substoichiometric conditions, 0.8 μM cofilin cut filamentous actin (2.2 μM) about every 270 monomer subunits and increased the depolymerization rate 5.7-fold at pH 7.1.2) Using cultured mammalian cell and Xnopus oocyte cell extracts, we identified two proteins, which bound to actin/cofilin comuln, to be Aipl and CAP.Yeast Aip1 was also found as a factor which suppresses the ts-phenotype of cof1 mutation. In Physarum polycepharum, a heat stress-induced cist-specific actin-binding protein was identified as Aip1. Aip1 suguments both actin filaments-severing and depolymerization-accelerating activities of cofilin.3) we identified a novel type of cofilin family member, cofilin-2, in D.discoideum. Cofilin- 2 consists of 143 amino acid residues. Cofilin-2 shows a significant homology (30.6% identity) to cof … More ilin-1 in its entire sequence, but does not retain some residues conserved among the cofilin family memners, suggesting that cofilin-2 belongs to a novel type of cofilin family. Purified cofilin-2 depolymerized actin filaments in a dose- and pH-dependent manner, but did not cosediment with actin filaments while cofilin-1 did. Cofilin-2 was not expressed in vegetative cells, and expresseion of coffin-2 is reduced during aggregation stage of development.4) we investigated the role of LIM-kinase 1, a protein that phosphorylates an actin depolymerizing protein, cofilin, in semaphorin 3A-induced growth cone collapse. We found that semaphorin 3A induces phosphorylation and dephosphorylation of cofilin at growth cones sequentially. A synthetic cell-permeable peptide containing a cofilin phosphorylation site inhibited LIM-kinase in vitro and in vivo, and essentially suppressed semaphorin 3A-induced growth cone collaplse. These data suggest that phosphorylation of cofilin by LIM-kinase is a critical signaling event in growht cone collapse by semaphorin 3A. Less