Meta-Biol

• Pathways

The human genome is predicted to encode 27 RAS guanine nucleotide exchange factors (GEFs) that promote the exchange of GDP for GTP on membrane-associated RAS in response to RAS-MAPK pathway activation by growth factors, hormones, cytokines and other stimuli (reviewed in Cherfils and Zeghouf, 2013; Cargnello and Roux, 2011). Nucleotide exchange stimulates a conformational change in RAS to facilitate its interaction with RAF, ultimately promoting the phosphorylation of downstream effectors MAPK3 and MAPK1 (also known as ERK1 and ERK2) (reviewed in Cseh et al, 2014; Vigil et al, 2010).