How KAI1/CD82 Suppresses Cancer Invasion and Metastasis

描述（由申请人提供）：KAI 1/CD 82是实体瘤的转移抑制因子。KAI 1/CD 82介导的转移抑制的机制仍然很难理解。最近的研究表明，KAI 1/CD 82诱导膜微区如脂筏和四跨膜蛋白富集微区（TEM）的重组，减弱生长因子和整合素信号传导，并抑制细胞突起和收缩。值得注意的是，我们还发现KAI 1/CD 82通过抑制癌细胞侵袭力来抑制癌症转移。因此，KAI 1/CD 82如何抑制癌细胞运动成为了解KAI 1/CD 82如何抑制癌症转移的突出问题。我们推测KAI 1/CD 82通过重组膜微区从而减少扩张和收缩过程以及由外向内的促有丝分裂信号传导来抑制癌细胞的迁移和侵袭。为了阐明KAI 1如何抑制癌症侵袭和转移，我们将首先通过i）鉴定将TEM物理连接到脂筏的CD 82分子中的结构元件，ii）系统地表征CD 82阳性TEM的蛋白质和脂质组分，和iii）分析含CD 82的TEM的运输和亚细胞定位。其次，我们将确定的机制，KAI 1/CD 82含有TEM调节细胞的运动活动，解决如何CD 82含有TEM使膜曲率和贩运。我们还将评估CD 82诱导的膜曲率和运输变化在i）膜运动活性，ii）促有丝分裂信号传导和iii）CD 82介导的癌症侵袭抑制中的作用。最后，我们将确定KAI 1/CD 82抑制体内癌症侵袭的机制，通过解决i）细胞运动活性CD 82抑制体内癌症侵袭的机制，ii）与CD 82物理或功能相关的蛋白质对CD 82介导的癌症侵袭抑制的贡献;和iii）上述分析的CD 82特征是否对其在体内抑制癌症侵袭至关重要。总之，拟议的研究将使我们能够i）理解KAI 1/CD 82如何调节细胞迁移，癌症侵袭和癌症转移作为膜微区的组织者，以及ii）揭示细胞运动和癌症转移调节的新机制，即，膜弯曲和运输调节侵袭和转移。通过对KAI 1/CD 82在体内外机制的深入研究，我们将对肿瘤的侵袭和转移有一个完整的认识，最终将KAI 1/CD 82发展成为肿瘤侵袭和转移的诊断标志物和治疗靶点。

DESCRIPTION (provided by applicant): KAI1/CD82 is a metastasis suppressor of solid tumors. The mechanism of KAI1/CD82- mediated metastasis suppression still remains largely elusive. Recent studies indicate that KAI1/CD82 induces the reorganization of membrane microdomains such as lipid rafts and tetraspanin-enriched microdomain (TEM), attenuates growth factor and integrin signaling, and inhibits cell protrusion and retraction. Notably, we also found that KAI1/CD82 suppresses cancer metastasis by inhibiting cancer cell invasiveness. Thus, how KAI1/CD82 inhibits cancer cell movement becomes the outstanding question to understand how KAI1/CD82 suppresses cancer metastasis. We hypothesize that KAI1/CD82 inhibits cancer cell migration and invasion through re-organizing membrane microdomains and consequently reducing protrusive and retraction processes and the outside-in mitogenic signaling. To elucidate how KAI1 suppresses cancer invasion and metastasis, we will first carry out the structural and functional characterization of KAI1/CD82-containing TEM by i) identifying the structural element(s) in CD82 molecule that physically links TEM to lipid rafts, ii) systematically characterizing the protein and lipid components of CD82-positive TEM, and iii) analyze the trafficking and subcellular localization of CD82- containing TEM. Secondly, we will determine the mechanism by which KAI1/CD82-containing TEM regulates the cellular motile activities by addressing how CD82-containing TEM renders membrane curvature and trafficking. We will also assess the roles of CD82-induced alterations in membrane curvature and trafficking in i) membrane motile activities, ii) mitogenic signaling, and iii) CD82-mediated suppression of cancer invasion. Finally, we will determine the mechanism by which KAI1/CD82 inhibits cancer invasion in vivo by addressing i) through which cellular motile activity CD82 suppresses cancer invasion in vivo, ii) the contributions of the proteins physically or functionally associated with CD82 to CD82-mediated suppression of cancer invasion; and iii) whether the CD82 features analyzed above are crucial for its suppression of cancer invasion in vivo. Together, the proposed study will enable us to i) understand how KAI1/CD82 regulates cell migration, cancer invasion, and cancer metastasis as an organizer for membrane microdomains and ii) unveil a novel mechanisms by which cell motility and cancer metastasis are regulated, i.e., membrane curvature and trafficking regulates invasion and metastasis. From the in-depth in vitro and in vivo mechanistic study of KAI1/CD82, we will develop an integrated understanding of cancer invasion and metastasis, which will ultimately lead to the development of KAI1/CD82 into a diagnostic marker and therapeutic target for cancer invasion and metastasis.