pREX1 is a guanine nucleotide exchange factor which activates a number of Rho family GTPases, such as Rac1 and RhoG, that are integral in regulating cell growth and motility. Recently, pREX1 has been implicated in a number of cancer signalling pathways; its expression was shown to be necessary for melanoma dissemination [1] and has been associated with increased metastatic phenotypes in both breast and prostate cancer [2, 3]. In conjunction with its role as a signal mediator in the oncogenically relevant ERK and PI3K/Akt pathways, these findings implicate pREX1 as an important signalling molecule in metastasis and abnormal cell growth. However, current understanding of the mechanisms leading to the activation and regulation of pREX1 is limited. Moreover, little is known about pREX1 and its interactions at a high-resolution, structural level.

Our initial studies of the catalytic DH-PH domains of pREX1 have focused on a structural and biophysical characterisation of the purified protein. The results confirm the importance of specific phosphorylation sites, and implicate a potential autoinhibition mechanism, in the regulation of pREX1 activity. Additionally, we have developed two novel assays utilising a FRET-based Rac1 biosensor in order to test pREX1 activity in both crude mammalian cell lysates and live cells. These assays will allow for future assessment of the effects of mutations and structural aberrations on the functional capacity of pREX1.