Functional Analysis of the VHL Tumor Suppressor Gene

DESCRIPTION: (provided by applicant) Approximately 30,000 Americans will develop renal cancer this year and nearly 12,000 will die from the disease. Mutation and/or inactivation of the von Hlippel about Lindau (VHL) gene occurs as an early, initiating event, promoting the development of most renal cell carcinoma (RCC). We have demonstrated that the binding of Elongins B & C protects VHL proteins from proteasomal degradation, in a manner similar to SOCS (suppressor of cytokine signaling) protein/elongin complexes. Expression of exogenous VHL gene product(s) in a renal cancer cell line (lacking wild type VHL) influences the growth and differentiation properties of confluent cells grown on extracellular matrix (ECM). In addition, VHL protects these cells from apoptosis. In accord with the function of VHL to inhibit apoptosis and suppress stress-related signaling pathways (e.g., hypoxia), our observation that VHL utilizes internal translation to synthesize a functional protein suggests a mechanism to assure adequate levels of VHL protein under conditions of suppressed cap-dependent translation. Taken together, these findings suggest the hypothesis that VHL may function as a tumor suppressor by suppression of stress signals (SOSS) through modification (e.g., ubiquitination) of key regulators of pathways involved in cell-cell, cell-ECM and stress-related signaling. The aims of this project are: (1) To determine the mechanism of VHL-mediated protection from apoptosis by assaying specific regulators of apoptosis common to UV irradiation, serum starvation, and glucose deprivation. We will also evaluate the pro-apoptotic potential of specific mutations in VHL and investigate whether these mutations drive apoptosis and provide selective pressure toward cells that are able to escape apoptosis; (2) To investigate the mechanism and functional imnportance of translational and post-translational regulation of VHL; (3) To identify potential targets of VHL activity, VHL-associating proteins will be compared under conditions of cell stress, low and high cell density and on plastic and ECM.