Heterotrimeric G proteins (???) are well known for their function in linking G protein- coupled receptors (GPCRs) to intracellular responses, and thereby playing essential roles in transmitting a wide variety of extracellular signals into regulation of countless physiological process. G proteins function as molecular switches whereby a GPCR promotes GDP release from the ? subunit (G?), followed by subsequent binding of GTP by G? and dissociation of G? and G??. G?-GTP and G?? can then regulate a variety of signaling proteins until the GTP hydrolysis activity of G? turns off signaling by generating the inactive G?-GDP, which then re- associates with G?? to complete the cycle of activation and inactivation. However, in uveal melanoma this tightly controlled G protein cycle is corrupted by a mutation in the closely related G?, ?q or ?1. Such mutations, occurring in over 90% of uveal melanoma, generate a constitutively active ?q or ?11 in which GTP hydrolysis activity is abrogated, thereby locking the G? in an active GTP bound state and turning ?q or ?11 into an oncogenic driver of this cancer. Uveal melanoma, the most common cancer of the eye in adults, metastasizes in up to 50% of uveal melanoma patients, and, once metastasis occurs, it is invariably fatal with an average survival of less than six months. There are currently no effective therapies for metastatic uveal melanoma, and thus there exists an urgent need to better understand the molecular mechanisms that promote the development of uveal melanoma. Based on numerous basic research studies on G protein function, it is clear that mutationally activated G? exhibit key cell biology properties, such as changes in subcellular localization, trafficking, lipid modification, degradation and activation of unique signaling pathways, that set them apart from the wild type G? counterpart. In uveal melanoma, it has been difficult to compare mutationally activated ?q or ?11 with wild type ?q or ?11 due to a lack of tools to differentiate between and effectively study the endogenous mutant versus wild type protein. Therefore, the objective of this project is to develop such a tool by using gene-editing approaches with uveal melanoma cell lines to generate cells in which the endogenous ?q or ?11, either the wild type or mutationally activated form, is fused in-frame to GFP. These genome-edited uveal melanoma cell lines will be a novel and much-needed tool to better understand how mutationally activated ?q or ?11 functions in uveal melanoma and to identify key aspects of regulation of mutationally activated ?q or ?11 that differ from that of wld type ?q or ?11.
Uveal melanoma, the most common adult eye cancer, is a deadly cancer in which up to 50% of patients experience untreatable metastases. A unique feature of uveal melanoma, compared to other cancers, is the presence of activating mutations in one of two closely related heterotrimeric G protein subunits, ?q or ?11. Understanding the mechanism of action and regulation of mutationally activated ?q or ?11 in uveal melanoma will provide new therapeutic targets for inhibiting aberrant ?q or ?11 function.
| Lapadula, Dominic; Farias, Eduardo; Randolph, Clinita E et al. (2018) Effects of Oncogenic G?q and G?11 Inhibition by FR900359 in Uveal Melanoma. Mol Cancer Res : |
| Chua, Vivian; Lapadula, Dominic; Randolph, Clinita et al. (2017) Dysregulated GPCR Signaling and Therapeutic Options in Uveal Melanoma. Mol Cancer Res 15:501-506 |
