UNC-73的in vitro功能及ced-10V12在線蟲touch cells所扮演的角色

Abstract

CED-10屬於Rho family GTPases的成員。而線蟲的ced-2, ced-5, ced-10, 和ced-12基因調控了細胞屍體吞噬過程以及生殖器官頂端細胞（distal tip cells）的遷移過程。雖然活體外的實驗顯示，活化的Rac會引發Swiss 3T3纖維母細胞的細胞膜表面皺褶的形成，然而對於活體內Rac的功能尚有許多探討的空間。當異位且過量表達constitutively activated ced-10（ced-10V12）時，線蟲的六個感受機械性感覺細胞（mechanosensory touch receptor neurons）會不正常的生長；而當表達過量的ced-10基因時，則會出現不同於ced-10V12的突變表型，如在尾部出現多餘的感覺細胞。這可能是由於細胞譜系（cell lineage）遭到改變所致。 unc-73在C. elegans的細胞遷移過程（cell migration）以及指引神經走向的過程（axon guidance）扮演著重要的角色。藉由生化實驗，我們證明瞭UNC-73的第一個DH domain對CED-10/Rac1具有催化GDP置換成GTP的能力。除此之外，也證明瞭在活體外，UNC-73可以和CED-5結合，再加上我們的遺傳分析，我們推測，UNC-73可能連接上游的訊息，進一步去活化CED-10，促使C. elegans活體內細胞遷移的過程。

CED-10 belongs to Rho family GTPases. In C. elegans, ced-2, ced-5, ced-10 and ced-12 control phagocytosis of cell corpses and migration of gonadal distal tip cells. Although in vitro function of Rac has been shown to regulate a signal transduction pathway in Swiss 3T3 cells that links extracellular signals to the formation of lamellipodia, the in vivo function of Rac remains to be explored. I found that ectopic expression of constitutively activated ced-10 (designated ced-10V12) results in many defects in six touch cells in C. elegans. Interestingly, ced-10 overexpression causes different phenotype from that of ced-10V12, such as extra PLM-like cell body. This may due to the alteration of cell lineage. unc-73 is required for cell migrations and axon guidance in C. elegans. Biochemical experiment suggests that the first DH domain of UNC-73 activates CED-10. In addition, we showed that UNC-73 and CED-5 physically interact in vitro, together with our genetic data, raising the possibility that UNC-73 may link upstream signaling complexes and CED-10, mediates cell migration in C. elegans.