Regulation of Cell Function by Matricellular Hevin

描述（由申请人提供）：本申请涉及基质细胞蛋白hevin的结构、调节和功能，这是分泌糖蛋白家族中SPARC（分泌蛋白酸性和富含半胱氨酸）中相对未被充分研究的成员。hevin也被称为SC-1， MAST 9， SPARC-like 1和ECM2， hevin被描述为一种肿瘤抑制基因，在某些组织的发育和形态发生中也具有重要作用。在体外，hevin已显示出死亡活性和内皮单层通透性的增强，部分作用是通过其减少这些细胞的局灶粘附复合物介导的。尽管最近关于hevin与肿瘤细胞增殖和/或转移相关的令人振奋的数据，但这些活动的机制仍然难以捉摸。我们提出hevin作为一种致命的、抗增殖的基质细胞蛋白，通过调节肿瘤与基质细胞的相互作用来抑制某些肿瘤的生长。因此，基于我们目前对hevin结构和功能的理解，本提案中描述的实验验证了3个假设：1)选择性死粘，细胞周期抑制和细胞外基质（ECM）产生的调节控制组织修复/血管生成和肿瘤进展的特定方面。在Aim 1中，我们研究了控制这些活动的机制，以及hevin的细胞表面受体/结合伙伴。2) hevin基因的调控及其翻译后修饰对于我们理解hevin如何作为肿瘤抑制因子至关重要。目的2在体外肿瘤细胞生长和血管生成的背景下解决这些参数。3) hevin与其同源物SPARC之间存在组织肿瘤特异性和蛋白质结构域特异性补偿，但hevin也具有独特的功能。目的3以靶向缺失SPARC、hevin和SPARC + hevin并伴有两种蛋白之间结构域互换的小鼠为实验对象，评估hevin对体内肿瘤生长和转移的影响。通过阐明hevin在体外对正常细胞和肿瘤细胞发挥各种调节活性的分子机制，我们预测将更好地了解肿瘤-宿主基质细胞在体内的相互作用，以及hevin在其中的作用。

DESCRIPTION (provided by applicant): This application addresses the structure, regulation, and function of the matricellular protein hevin, a relatively understudied member of the SPARC (secreted protein acidic and rich in cysteine) family of secreted glycoproteins. Also known as SC-1, MAST 9, SPARC-like 1, and ECM2, hevin has been described as a tumor-suppressor gene that also features prominently in the development and morphogenesis of certain tissues. In vitro, hevin has demonstrated deadhesive activity and enhancement of endothelial monolayer permeability, effects mediated in part by its diminishment of focal adhesion complexes in these cells. Despite recent provocative data regarding the association of hevin with tumor cell proliferation and/or metastasis, mechanisms accounting for these activities have remained elusive. We propose that hevin acts as a deadhesive, anti-proliferative matricellular protein that suppresses the growth of certain tumors via its modulation of tumor-stromal cell interactions. Accordingly, experiments described in this proposal test 3 hypotheses, based on our current understanding of hevin structure and function: 1) Selective deadhesion, cell-cycle inhibition, and regulation of extracellular matrix (ECM) production control specific aspects of tissue repair/angiogenesis and tumor progression. In Aim 1, we examine mechanisms governing these activities, as well as a cell-surface receptor/binding partner for hevin. 2) Regulation of the hevin gene and its posttranslational modifications are critical to our understanding of how hevin might act as a tumor suppressor. Aim 2 addresses these parameters in the context of tumor cell growth and angiogenesis in vitro. 3) There is both tissue tumor-specific and protein domain-specific compensation between hevin and its homolog SPARC, but hevin also has unique functions. Aim 3 features mice with targeted deletions of SPARC, hevin, and SPARC plus hevin, coupled with domain swaps between the two proteins, to evaluate the effect of hevin on tumor growth and metastasis in vivo. From an elucidation of molecular mechanisms by which hevin exerts its various regulatory activities on normal and tumor cells in vitro, we predict a better understanding of tumor-host stromal cell interactions in vivo, and the role of the matricellular protein hevin therein.