HIF-1

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。细胞的形状主要由其内部肌动蛋白细胞骨架结构决定，并受到局灶粘连的影响，后者构成细胞外基质（ECM）、整合素受体系统和肌动蛋白支架之间的连接点。为了响应外部粘附信号或内部产生的信号，细胞重新排列其肌动蛋白细胞骨架网络，从而改变整合素相关信号转导网络的组装。受细胞形状和信号转导联合变化影响的关键生物过程包括细胞迁移、增殖、转化和凋亡，这使得阐明所涉及的机制引起了相当大的兴趣。HEF1和相关蛋白p130Cas和Efs/Sin定义了局灶黏附相关信号蛋白Cas （crk相关底物）家族。对这些蛋白的机制研究已经明确了它们在细胞粘附和细胞迁移过程中的作用，并概述了它们功能的一系列上游诱导剂和下游介质。然而，我们的工作也证明了HEF1具有与细胞凋亡和细胞分裂相关的其他独特活性。这些离散的活动源于HEF1加工形式的功能。在某些生长环境下，28kd羧基末端形式诱导细胞圆缩并启动p53依赖的死亡信号，与p130Cas的促生存活性相反。有趣的是，有丝分裂中产生的55 kD胺端HEF1易位到有丝分裂纺锤体；我们最近已经确定，改变不同形式HEF1的表达水平和比例，从而增加全长HEF1的丰度，而不是55 kD形式的HEF1，会导致有丝分裂失败，包括多极纺锤体的发育，细胞分裂时脱落失败，以及G1期细胞的积累。这组缺陷与报道的涉及中心体功能的蛋白质的缺陷是一致的，基于包括周期蛋白B稳定性的调节，以及通过中心体迁移到细胞质分裂位点的分离许可，以及控制肌动球蛋白环收缩功能的蛋白质（如p160ROCK）的传递。我们还确定内源性HEF1定位于中心体，并进一步表明错误表达的HEF1影响cyclin B的积累和RhoA （p160ROCK激活剂）的激活。基于这些和其他结果，我们提出HEF1具有独特的功能，可以通过有丝分裂和细胞分裂调节细胞周期进程，并且这种作用与其在附着相关的生存信号传导中的作用是可分离的。我们的目标是确定HEF1在间期和有丝分裂细胞中的功能是使用共同的还是独特的效应物。

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. The shape of a cell is determined primarily by its internal actin cytoskeletal architecture and influenced by focal adhesions, which constitute points of linkage between the extracellular matrix (ECM), the integrin receptor system and actin scaffolds. In response to external adhesive signals or internally generated cues, cells rearrange their actin cytoskeletal networks, thereby altering assembly of integrin-associated signal-transducing networks. Critical biological processes affected by the combined changes in cell shape and signal transduction include cell migration, proliferation, transformation and apoptosis, making the elucidation of the mechanisms involved of considerable interest. HEF1, and the related proteins p130Cas and Efs/Sin, define the Cas (Crk-associated substrate) family of focal adhesion-associated signaling proteins. Mechanistic studies of these proteins has defined their roles in the processes of cell adhesion and cell migration, and outlined a set of upstream inducers and downstream mediators of their function. However, our work has also demonstrated that HEF1 possesses additional unique activities relevant to apoptosis and cell division. These discrete activities derive from the function of processed forms of HEF1. A 28 kD carboxyterminal form induces cellular rounding and initiates p53-dependent death signaling under some growth circumstances, opposing a pro-survival activity of p130Cas. Intriguingly, a 55 kD aminoterminal HEF1 form arising in mitosis translocates to the mitotic spindle; and we have recently determined that altering the expression level and ratios between different forms of HEF1 so as to increase abundance of full length HEF1 versus the 55 kD form results in a failure of mitosis that involves development of multipolar spindles, failure of abscission at cytokinesis, and accumulation of cells at G1. This suite of defects is compatible with defects reported for proteins involved in functions at the centrosome, based on activities that include regulation of cyclin B stability, and licensing of abscission through centrosomal migration to the site of cytokinesis and delivery of proteins such as p160ROCK that control actomyosin ring contractile function. We have also determined that endogenous HEF1 localizes to the centrosome, and further shown that mis-expressed HEF1 affects cyclin B accumulation and activation of RhoA, a p160ROCK activator. Based on these and other results, we propose that HEF1 has a unique function as a regulator of cell cycle progression through mitosis and cytokinesis, and that this effect is separable from its roles in attachment-related survival signaling. Our goal is to determine whether HEF1 uses common or unique effectors for its functions in interphase versus mitotic cells.