– Cytoplasmic Protein NCK1 (NCK1) is a cytoplasmic protein that contains one SH2 domain and three SH3 domains. NCK1 is a member of the adapter family, which associates with tyrosine-phosphorylated growth factor receptors, such as KDR and PDGFRB, or their cellular substrates. NCK1 maintains low levels of EIF2S1 phosphorylation by promoting its dephosphorylation by PP1. NCK1 plays a role in the DNA damage response, but not in the detection of the damage by ATM/ATR. It is also involved in transducing signals from receptor tyrosine kinases to downstream signal recipients, such as ELK1-dependent transcriptional activation in response to activated Ras signaling.