MAPK3 (Mitogen-Activated Protein Kinase 3, also known as ERK1) is a Protein Coding gene. The protein encoded by the ERK1 gene is a member of the MAP kinase family. 3 alternatively spliced human isoforms have been reported. The protein is a serine/threonine kinase which acts as an essential component of the MAP kinase signal transduction pathway. MAPK1/ERK2 and MAPK3/ERK1 are the 2 MAPKs that play an important role in the MAPK/ERK cascade. They participate also in a signaling cascade initiated by activated KIT and KITLG/SCF. ERK1 is widely expressed in the small intestine, colon, and other tissues. Diseases associated with MAPK3 include Neutrophil Migration and Pertussis.