THE STRUCTURE AND FUNCTION OF CYTOPLASMIC DYNEIN

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。分子运动蛋白在多种细胞内运输过程中起作用，包括细胞器的组织及其运输、染色体分离、轴突运输和信号通路。运动依赖过程对细胞和组织的生长、增殖和分化至关重要。运动功能在发育过程中是如何调节的，以及运动功能障碍与许多医学问题（包括神经退行性疾病、先天性染色体综合征和出生缺陷）的关系是当前研究活动的重点。我们的工作重点是微管运动细胞质动力蛋白，以及关于这种单一运动异构体如何完成多重任务的重要且未解决的问题。动力蛋白是如何针对特定的货物和/或细胞的位置和结构？我们的目标将解决三种可能有助于动力蛋白靶向的非排他性机制。(1)首先，细胞质动力蛋白包含多个亚基。单个亚基或亚基结构域可以指定动力蛋白附着的位置和部位。为了验证这一假设，我们将询问轻中间体和中间链多肽内的结构域是否赋予特定功能。诱变和分子遗传方法将用于破坏结构域功能和突变表型将被表征。(2)其次，动力蛋白亚基的翻译后修饰可能会控制亚基是否有能力结合高亲和力的货物。与John Yates博士（Scripps研究所）合作，将使用质谱法确定动力蛋白复合物亚基磷酸化的位点。随后，鉴定的磷酸化位点将发生突变，以模拟各自亚基的磷酸化或未磷酸化状态。我们将分析表达突变亚基的转基因所产生的表型，以揭示动力蛋白磷酸化调控的功能意义。(3)在第三种机制中，特定的结合伙伴或效应蛋白可能介导动力马达靶向特定的货物或位置。我们将继续对前一阶段确定的候选相互作用蛋白进行功能分析，并将继续对其他相互作用位点进行二次测试。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Molecular motor proteins function in a multitude of intracellular transport processes that include the organization of organelles and their transport, chromosome segregation, axonal transport, and signaling pathways. Motor dependent processes are critical for the growth, proliferation, and differentiation of cells and tissues. How motor function is regulated in a developmental context, and the relationship of motor dysfunction to numerous medical problems including neurodegenerative disease, congenital chromosomal syndromes, and birth defects is a current focus of research activity. Our work is focused on the microtubule motor cytoplasmic dynein, and the important and unanswered question regarding how this single motor isoform accomplishes multiple tasks. How is dynein targeted to specific cargoes and/or cellular locations and structures? Our aims will address three non-exclusive mechanisms that potentially contribute to dynein targeting. (1) First, cytoplasmic dynein contains multiple subunits. The individual subunits or subunit domains could specify where, and to what, dynein is attached. To test this hypothesis we will ask whether domains within the light intermediate and the intermediate chain polypeptides confer specific functions. Mutagenesis and molecular genetic approaches will be used to disrupt domain function and the mutant phenotypes will be characterized. (2) Second, the posttranslational modification of dynein subunits might control whether subunits are competent to bind a cargo with high affinity. Collaboration with Dr. John Yates (Scripps Research Institute) will define the sites of phosphorylation on subunits within the dynein complex using a mass spectrometry approach. Subsequently, the phosphorylation sites identified will be mutated to mimic the phosphorylated or unphosphorylated state of the respective subunit. The phenotypes produced by transgenes that express the mutant subunits will be analyzed to reveal the functional significance of dynein phosphoregulation. (3) In a third mechanism, specific binding partners or ¿¿effector¿¿ proteins might mediate the targeting of the dynien motor to specific cargoes or locations. We will pursue the functional analysis of candidate interacting proteins identified in the previous period and will continue with secondary tests on other interacting loci.