細胞移動的初步機制，必須在基材上進行延展。細胞延展在癌細胞轉移中扮演?一個關鍵性的調控步驟。因此透過調控細胞延展的研究可以提供防止細胞轉移的治療策略。細胞延展和爬行都涉及actin聚合在細胞膜的前緣和尾部抽離。調節細胞延展和爬行雖已被廣泛研究，但詳細分子機制仍不清楚。根據以往的研究，Mob2蛋白會藉由參與actin細胞骨架的重新排列進而影響?經纖維生長。此外，Mob2在酵母菌的極性生成和果蠅感光細胞的發育過程中也影響actin細胞骨架。但是目前沒有研究指出Mob2是否會影響細胞延展和細胞爬行功能。在本研究中，我們發現人類纖維腫瘤(HT1080) 細胞展延需要hMOB2蛋白參與。免疫細胞染色結果顯示，人類纖維腫瘤(HT1080) 細胞爬行時，hMOB2會分佈在爬行的細胞前緣。進一步探討hMOB2是否參與細胞移動，我們利用shRNA的方式?低細胞內hMob2蛋白的表現觀察細胞延展和細胞爬行的情況，hMOB2在人類纖維腫瘤(HT1080) 細胞會延遲細胞展延。除此之外，過量表達野生型hMOB2蛋白會促進hMOB2累積在細胞的前緣和增強細胞延展能力。為了更進一步瞭解hMOB2在細胞移動時的功能性區域，我們建立了持續表達突變型（A107G、Y110A）的hMOB2蛋白。結果顯示突變型的hMOB2蛋白會影響hMOB2蛋白在細胞前緣的累積及延遲細胞延展的能力。綜合以上結果，推測hMOB2蛋白會透過影響其表?在細胞前緣，來調控細胞展延。然而在人類纖維腫瘤細胞 (HT1080)移動的速率，?低細胞內hMob2，表現野生型和突變型的細胞株中，細胞移動的速率並沒有顯著的差異。過量表達野生型hMOB2蛋白會形成較多的板狀偽足結構，並且會以群體方式來移動。此研究結果提供對細胞延展的分子機制有更進一步的了解。 Cell spreading is an initial mechanism for cell migration which plays a vital role in cancer development. Cell spreading has been shown to act as one of the key regulating steps between static and metastatic transition of a cancer cell. Hence, by identifying regulatory networks controlling cell spreading, it may provide valuable information and therapeutic strategies for preventing tumor metastasis. Both cell spreading and cell migration involve actin polymerization at the leading edge of plasma membrane follow by cell retraction at the rear end of cells. The molecular mechanisms in regulating cell spreading and cell migration have been extensively studied but remain unclear. Studies from yeast, Drosophila to mammalian cells have shown that MOB2 protein plays an important role in controlling the cell morphology changes by affecting cell polarity and rearrangement of actin cytoskeleton. Currently there is no research done to study the function of Mob2 in cell spreading and cell migration. In this study, we identified hMOB2 protein which plays a significant role in promoting cell spreading in HT1080 human fibrosarcoma cells. Our results showed that hMOB2 was detected at the leading edge of migrating HT1080 human fibrosarcoma cell. To study whether hMOB2 was involved in cell motility, we downregulated hMOB2 expression using RNA interference and found that cell spreading was delayed in HT1080 cells. In addition, we observed that overexpression of hMOB2 enhanced cell spreading in HT1080 cells and enhanced its accumulation at the leading edge. Furthermore, to determine the possible functional domain in cell motility, we successfully generated A107G, Y110A point mutated hMOB2 stable cell lines. Over-expressed point mutated hMOB2 expression delayed cell spreading and suppressed its accumulation at the leading edge. These observations suggested that hMOB2 affects cell spreading by regulating its expression at leading edge. No significant difference was observed in the migration rate between the different HT1080 cell populations when the percentage of gap closure was determined. However, over-expressed wild type hMOB2 induced broad lamellipodial structures and moved as a coherent group when compared with parent cells. These studies provided additional information on the molecular mechanisms which control cell spreading.
