Regulation of Cell Function by Matricellular Hevin

描述(申请人提供)：本申请涉及母细胞蛋白Hevin的结构、调节和功能，Hevin是SPARC(分泌型酸性蛋白和富含半胱氨酸的分泌型糖蛋白)家族中研究相对较少的成员。Hevin也被称为SC-1、Mast 9、SPARC-like 1和ECM2，已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表现出致命的活性和增强内皮细胞单层通透性，其作用部分是通过减少这些细胞中的焦点黏附复合体来实现的。尽管最近有关于Hevin与肿瘤细胞增殖和/或转移相关的挑衅性数据，但这些活性的机制仍然难以捉摸。我们认为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，根据我们目前对Hevin结构和功能的理解，本提案中描述的实验测试了3个假说：1)选择性死亡结合、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。在目标1中，我们研究了控制这些活性的机制，以及Hevin的细胞表面受体/结合伙伴。2)对Hevin基因及其翻译后修饰的调控对于我们理解Hevin可能作为肿瘤抑制因子的作用至关重要。目的2在肿瘤细胞生长和体外血管生成的背景下解决这些参数。3)Hevin与其同源基因SPARC之间存在组织肿瘤特异性和蛋白质结构域特异性代偿，但Hevin也具有独特的功能。目的3以靶向缺失SPARC、Hevin和SPARC+Hevin的小鼠为实验对象，结合两种蛋白之间的结构域交换，评价Hevin对体内肿瘤生长和转移的影响。通过阐明Hevin在体外对正常和肿瘤细胞发挥各种调节作用的分子机制，我们可以更好地理解体内肿瘤与宿主基质细胞的相互作用，以及母细胞蛋白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.