Role of Myosin in Intestinal Brush Border Function

肌球蛋白在从肠道和结肠上皮细胞分离的刷状边缘的结构和功能中的作用将被研究。在刷状边缘的细胞骨架中，肌球蛋白与两个结构域相关：一个由末端网组成，在那里它与微绒毛核心束肌动蛋白细丝交联，另一个是围绕末端网的肌动蛋白细丝收缩环。肌球蛋白的两个子集可以从笔刷边缘区别提取：一个参与终末网络收缩，另一个不参与。这项研究的目的是确定这两个子集的分子基础。在刷状边缘表达一种以上肌球蛋白同工酶的可能性，以及肌球蛋白同工酶与肌球蛋白亚群之间的关系将被研究。肌球蛋白的每个亚集相对于末端网的两个主要结构域的定位也将被确定。由于在胚胎发育过程中，肌球蛋白同工酶的表达和亚群的定位与肠道发育的正常顺序有关，因此，肌球蛋白同工酶的环状结构在胚胎发育过程中较早地被组织起来。最后，一个肌球蛋白亚群的稳定结构关联表明，它可能与细胞骨架中的肌动蛋白以外的蛋白相互作用。在刷子边缘结合肌球蛋白的蛋白质将被识别和定位。这项研究的结果可能表明，肌球蛋白在刷状边缘功能中扮演的角色不止一个，而且特定的肌球蛋白在单个细胞骨架系统中执行特定的功能。这为细胞骨架蛋白通常由多基因家族编码这一普遍观察增加了新的意义。

The role of myosin in the structure and function of brush borders isolated from intestinal and colonic epithelial cells will be investigated. In the brush border cytoskeleton, myosin is associated with two structural domains: one comprising the terminal web where it crosslinks the microvillus core bundles of actin filaments, and the other a contractile ring of actin filaments that surrounds the terminal web. Two subsets of myosin are differentially extractable from the brush border: one that is involved in terminal web contraction and one that is not. The aim of this research is to determine the molecular basis for the two subsets. The possiblity that more than one isozyme of myosin is expressed in the brush border, and the relationship between myosin isozymes and the subsets of myosin will be investigated. The localization of each of the subsets of myosin with respect to the two major structural domains of the terminal web will also be determined. Because the circumferential ring is organized long before the interroolet region during embryogenesis, the findings on myosin isozyme expression and subset localization will be related to the normal sequence of intestinal development. Finally, the stable structural association of one myosin subset indicates the likelihood that it interacts with more than actin in the cytoskeleton. Proteins that bind myosin in the brush border will be identified and localized. The results of this research may indicate that myosin plays more than one role in brush border function and that a specific myosin performs a specific function within a single cytoskeletal system. This adds new significance to the general observation that cytoskeletal proteins are frequently encoded by multigene families.