| The cytoplasmic domain of the IGF IR was used to screen a human fetal brain library and two isoforms of the 14 3 3 family were identified . 14 3 3 proteins are a highly conserved family of proteins which have recently been shown to interact with other components of the mitogenic and apoptotic signaling pathways , including Raf , BAD , Bcr / Bcr Abl , middle T antigen , Ksr , PKC , PI 3 kinase , ASK 1 kinase , and cdc25C phosphatase . ^^^ |