EFS (also known as SIN) is a member of the CAS family. It is involved in T lymphocyte development and immune system maturation. It has also been linked to several disorders, such as cancers and Chediak-Higashi syndrome []. CAS (Crk-associated substrate) family members are adaptor proteins that contain a highly conserved N-terminal SH3 domain, an adjacent unstructured domain (substrate domain) containing multiple tyrosine phosphorylation sites that enable binding by SH2-domain containing proteins, a serine-rich four-helix bundle, and a FAT-like C-terminal domain. Most of these domains mediate protein-protein interactions. Through these interactions, they assemble larger signaling complexes that are essential for cell proliferation, survival, migration, and other processes []. The CAS family consists of four members: BCAR1, HEF1, EFS, and CASS4 [].
