School of Science Division of Life Science 31 G Protein-coupled Receptors in Cell Signaling Supervisor: WONG Yung Hou / LIFS Student: LIU Zhiyin / BCB Course: UROP2100, Fall Melatonin receptors (MT1 and MT2 in mammals) are G protein-coupled receptors (GPCR) which play an important in signal cascade of melatonin. As mentioned in the last research report, we applied Tango assay to determine the dimerization of MT1 and MT2 and firstly attempted to construct plasmids expressing melatonin receptors and TEV protease but failed. Therefore, the purpose of the research this semester was to find out the key factors for successful transformation and improve the transformation efficiency. The results showed that the ratio of vector and insert as well as plasmid concentration were imperative for transformation efficiency, by which we can optimize the original method. G Protein-coupled Receptors in Cell Signaling Supervisor: WONG Yung Hou / LIFS Student: LO Vincent / SSCI Course: UROP1100, Summer Nm23-H1 (Non-metastatic protein 23 H1) is known to be a metastasis suppressor for most cancers. Meanwhile, SUSD2 (Sushi domain-containing 2) can be both a metastasis suppressor and promoter concomitantly. Recent research shows they may have a unique relationship inside the cancer cells. Thus, we measured the protein level of Nm23-H1 and SUSD2 in both breast and lung cancer cell lines by immunoblotting in this project. Based on the result, we proposed that PI3K/Akt and Wnt signaling pathways would be the feasible interaction pathways between two proteins in different cancer cells. Additionally, miRNA and galectin-1 may also involve in their connection. Therefore, we will work on their protein-protein interaction in the future. We believe finding out their association will advance the current anticancer drugs and therapy. G Protein-coupled Receptors in Cell Signaling Supervisor: WONG Yung Hou / LIFS Student: YAU Hiu Laam / BCB Course: UROP1100, Fall UROP2100, Spring Intense research has been engaging in the mechanism of the Gα-mediated downstream signalling pathway since the discovery of GPCR signalling in the 1990s. As a component of heterotrimeric G protein, the Gβγ subunit that is dissociated from the Gα subunit upon receptor activation also plays a crucial role in regulating downstream effectors in GPCR signalling. Due to the redundancy of Gβγ and Gα signalling pathways, the effector interacting capability of Gα must be first removed so that the Gβγ-mediated signalling response induced by receptor activation can be observed in vitro. In this study, we attempted to identify the critical residues or motifs responsible for the effector interaction in Gαi1 by studying the crystal structures of Gαi1 and adenylyl cyclase 5.