Identifying the ubiquitin ligase complex that regulates the NF1 tumor suppressor and Ras
Menée in vitro et in vivo, cette étude met en évidence des mécanismes par lesquels, en régulant l'expression du gène Ras et en stabilisant la protéine NF1, la protéine Cul3 joue un rôle de suppresseur de tumeurs dans les glioblastomes
The NF1 tumor suppressor protein, neurofibromin, is a negative regulator of Ras. Neurofibromin is dynamically regulated by the proteasome and its degradation and re-expression are essential for maintaining appropriate levels of Ras-GTP. Like p53, NF1/neurofibromin can be inactivated in cancer by both mutations and excessive proteasomal destruction; however, little is known about the mechanisms that underlie this latter process. Here we show that a Cullin 3 (Cul3)/KBTBD7 complex controls both the regulated proteasomal degradation of neurofibromin and the pathogenic destabilization of neurofibromin in glioblastomas. Importantly RNAi-mediated Cul3 ablation and a dominant-negative Cul3 directly stabilize neurofibromin, suppress Ras and ERK, and inhibit proliferation in an NF1-dependent manner. Moreover, in glioblastomas where neurofibromin is chronically destabilized, Cul3 inhibition re-stabilizes the protein and suppresses tumor development. Collectively these studies demonstrate a previously unrecognized role for Cul3 in regulating Ras and provide a molecular framework that can be exploited to develop potential cancer therapies.