Regulation of Myosin Function by Protein Kinases and Light Chains

细胞在表面爬行，伸展和收缩表面突起，改变形状，吞噬其他有机体，吸收液体营养，并通过分裂成两半。这些不同形式的细胞运动是由肌球蛋白驱动的，肌球蛋白是一种非凡的分子马达，它将化学能转化为一种力量，用于沿着或拉动肌动蛋白细丝。我们的研究集中在两类普遍存在的肌球蛋白：肌球蛋白-I和肌球蛋白-II。肌球蛋白-I连接细胞膜和肌动蛋白细丝，并参与驱动膜形状的变化。肌球蛋白-II，也被称为肌肉肌球蛋白，组装成双极细丝，收缩肌动蛋白细丝网络。我们正在研究三种调节肌球蛋白-I和肌球蛋白-II活性的机制。这些调节过程对于确保移动或力的产生只在需要的地方和时间发生在细胞中是至关重要的。我们的第一个研究项目涉及一种名为MHCK-A的蛋白激酶，它可以阻止肌球蛋白-II组装成细丝。有趣的是，MHCK-A具有一种新型的蛋白激酶结构域，是被称为α-激酶的非典型蛋白激酶家族的创始成员。我们发现MHCK-A的结构和催化性质与传统的蛋白激酶有很大的不同。我们将进一步研究MHCK-A的结构、催化和调节特性，以期对这个知之甚少但很重要的激酶家族有新的认识。我们的第二个项目涉及两个新的轻链，MlcB和MLCC，我们发现它们是肌球蛋白-I的组成部分。肌球蛋白轻链具有稳定和调节肌球蛋白运动区的功能，其大小通常为16 kDa，而MlcB和MLCC的大小仅为8 kDa。我们将研究MlcB和MLCC如何结合、稳定和调节肌球蛋白-I活性，并研究它们与其他蛋白质结合的可能性。我们的第三个项目涉及一种蛋白激酶PakB，它可以激活肌球蛋白-I。我们将继续进行我们所做的有趣的观察，表明pakB在调节肌球蛋白-I将质膜连接到潜在的肌动蛋白细丝网络的能力中发挥关键作用。我们的发现将促进对肌球蛋白依赖的细胞运动如何调节的基础知识。它将提供有价值的信息，可用于产生特定的抑制物来阻止运动过程，这可能对癌症转移或炎症等疾病有用，细胞迁移在这些疾病中发挥核心作用。HQP将发展一套多样化和全面的研究技能，拥有分子生物学、结构生物学、酶学和细胞生物学方面的专业知识。

Cells crawl over surfaces, extend and retract surface protrusions, change shape, engulf other organisms, take up liquid nutrients and divide by splitting into two. These varied forms of cell movement are driven by myosin, a remarkable molecular motor that converts chemical energy into a force that is used to travel along, or pull on, actin filaments. Our research focuses on two ubiquitous classes of myosin: myosin-I and myosin-II. Myosin-I links cell membranes to actin filaments and is involved driving membrane shape changes. Myosin-II, also called muscle myosin, assembles into bipolar filaments that contract networks of actin filaments. We are investigating three mechanisms that regulate myosin-I and myosin-II activity. These regulatory processes are critical to ensure that movement or force generation occurs in the cell only where and when it is required. Our first research project involves a protein kinase, termed MHCK-A, that blocks the assembly of myosin-II into filaments. Interestingly, MHCK-A has a novel type of protein kinase domain and is the founding member of a family of atypical protein kinases termed the alpha-kinases. We have shown that the structure and catalytic properties of MHCK-A differ considerably from those of conventional protein kinase. We will further study the structure, catalytic and regulatory properties of MHCK-A in order to shed new light on this poorly understood but important kinase family. Our second project concerns two novel light chains, MlcB and MlcC, that we discovered as components of myosin-I. Myosin light chains, which stabilize and regulate the myosin motor domain, are normally 16 kDa in size, but MlcB and MlcC are only 8-kDa in size. We will examine how MlcB and MlcC bind to, stabilize and regulate myosin-I activity, and will also investigate the possibility that they bind to other proteins. Our third project involves a protein kinase, PakB, that activates myosin-I. We will pursue an intriguing observation that we have made which indicates that PakB plays a critical role in regulating the ability of myosin-I to link the plasma membrane to the underlying actin filament network. Our findings will advance the basic knowledge of how myosin-dependent cell motility is regulated. It will provide valuable information that can be employed to generate specific inhibitors to block motile processes, which could be useful for diseases such as cancer metastases or inflammation in which cell migration plays a central role. HQP will develop a diverse and comprehensive research skill set with expertise in molecular biology, structural biology, enzymology and cell biology.