JIP1 (JNK-interacting protein-1) is a cytoplasmic protein that possesses an N-terminal JNK-binding domain and a C-terminal SRC homology 3 (SH3) domain. JIP1 selectively bind to JNK, but not to the ERK or p38 MAP kinases. In addition to JNK, JIP1 binds to specific proteins of JNK pathways, including MKK7, MLK3, and DLK, all at separate binding sites. JIP1 has been identified in brain and kidney tissues, whereas JIP2a, JIP2b, and JIP3 are specifically expressed in the brain. Overexpression of JIP1 causes cytoplamic retention of JNK, thereby preventing its nuclear accumulation and the subsequent activation of the JNK pathways, indicating that JIP1 acts as a cytoplasmic anchor for JNK.