Meta-Biol

• Pathways

Upon growth factor stimulation, RAF1 S259 (or S365 and S214 in BRAF and ARAF respectively) is dephosphorylated by PP2A and/or PP1, abrogating one of the YWHAB/14-3-3 binding sites (Terai et al, 2005; Ory et al, 2003; Kubicek et al, 2002; Jaumot et al, 2001; Rommel et al, 1996; reviewed in Roskoski, 2010; Matallanas et al, 2011). Release of 14-3-3 binding from the N-terminal site promotes a conformational change that exposes the membrane and RAS interacting RBD and CRD and facilitates recruitment of RAF to the plasma membrane where it binds RAS:GTP (Kubicek et al, 2002; Goetz et al, 2003; Ory et al, 2003). Dephosphorylation of S259/S365/S214 may also promote dimerization of RAF monomers by replacing the intramolecular 14-3-3 binding interaction with an intermolecular one (Rushworth et al, 2006; Weber et al, 2001; Ritt et al, 2010; reviewed in Matallanas et al, 2011). Although the PP2A-mediated dephosphorylation is shown as occurring before both YWHAB displacement and recruitment of RAF to the plasma membrane, the order of and relationship between these events is not completely clear. In addition, the displacement of 14-3-3 and recruitment of RAF1 to the membrane is also promoted by a direct interaction with cell cycle protein Prohibitin (PHB; Rajalingam et al, 2005; reviewed in Rajalingam and Rudel, 2005; Chowdhury et al, 2014).