Molecular Mechanism in Regulation of Neuronal Dendritic Morphology

(1)为了研究dreplasma与其他肌动蛋白相关蛋白的关系，我们对dreplasma、肌球蛋白、肌动蛋白、肌球蛋白、α-肌动蛋白、caldeson和gelsoin进行了纯化，并与肌动蛋白丝进行了各种共纯化研究。Dreplastin以1：5的化学计量与肌动蛋白丝结合，解离常数（Kd）为1.2x10^<-7>M。Dreplastin不表现出任何肌动蛋白成核、肌动蛋白切断或肌动蛋白加帽活性，也不交联肌动蛋白丝。dreethyl不影响凝溶胶蛋白的活性或钙调蛋白和细丝蛋白的肌动蛋白结合活性，但强烈抑制原肌球蛋白的肌动蛋白结合活性，以及α-辅肌动蛋白和肌成束蛋白的肌动蛋白结合和肌动蛋白交联活性。Drexanthin对肌动球蛋白相互作用有抑制作用，可能是神经元内肌动球蛋白相互作用的肌动蛋白连接调节蛋白。(2)神经元树突棘的形态学变化被认为参与了突触可塑性的表达。我们已经研究了负责脊柱形态学变化的分子机制，重点是一种蛋白质，结合肌动蛋白丝，dreplastin，这是集中在神经元。我们发现，成人型dreplasma是本地化的树突棘在前脑的大鼠，在那里它结合到细胞骨架的脊柱。含drebrin的细胞骨架由drebrin、肌动蛋白、肌球蛋白和凝溶胶蛋白组成。在体外实验中，drepletin抑制肌动蛋白丝在涂有肌球蛋白的玻璃表面上的运动，并降低肌球蛋白的肌动蛋白依赖性ATP酶活性。这些结果表明，drepletin调制内的棘肌动球蛋白的活动，并在突触的结构为基础的可塑性中发挥作用。

(1) In order to find out the relationships between drebrin and other actin associated proteins, drebrin, myosin, actin, toropomyosin, alpha-actinin, caldeson and gelsoin were purified, and various co-purification study with actin filament have been done. Drebrin binds to actin filaments at a stoichiometry of 1 : 5, with a dissociation constant (Kd) of 1.2x10^<-7>M.Drebrin does not exhibit any actin-nucleating, actin-severing or actin-capping activity, nor does it crosslink actin filaments. Drebrin did not affect the activity of gelsolin or actin binding activity of caldesmon and filamin, but strongly inhibited the actin binding activity of tropomyosin, and the actin binding and actin cross-linking activities of alpha-actinin and fascin. Drebrin has an inhibitory effect on actomyosin interation and might be an actin-linked regulatory protein of actomyosin interaction within neurons.(2) The morphological changes of dendritic spines of neurons have been postulated to participate in the expression of synaptic plasticity. We have examined the molecular mechanisms responsible for the changes in spine morphology, focusing on a protein that binds to actin filaments, drebrin, that is concentrated in neurons. We found that adult-type drebrin is localized in the dendritic spines in the forebrain of the rat, where it binds to the cytoskeleton of the spine. The drebrin-containing cytoskeleton consisted of drebrin, actin, myosin and gelsolin. In vitro, drebrin inhibited the movement of actin filaments on a glass surface that had been coated with myosin and reduced the actin-dependent ATPase activity of myosin. These results suggest that drebrin modulates the acto-myosin activity within spines and plays a role in the structure-based plasticity of synapses.