XIAP

XIAP is the acronym for "X-linked inhibitor of apoptosis protein" (see also XIAP gene).

The XIAP protein is a multifunctional protein that not only regulates caspases and apoptosis, but also modulates inflammatory signaling and immunity, copper homeostasis, mitogen-activated kinase signaling, cell proliferation, as well as cell invasion and metastasis.

It acts as an E3 ubiquitin protein ligase that regulates NF-kappa-B signaling.

Targets of its E3 ubiquitin protein ligase activity include: RIPK1, CASP3, CASP7, CASP8, CASP9, MAP3K2/MEKK2, DIABLO/SMAC, AIFM1, CCS, and BIRC5/Survivin.

The XIAP protein acts as an important regulator of innate immune signaling by regulating Nod-like receptors (NLRs). It suppresses ripoptosome formation by ubiquitinating RIPK1 and CASP8. The XIAP protein acts as a positive regulator of Wnt signaling and ubiquitinates TLE1, TLE2, TLE3, TLE4, and AES.