Transmembrane BAX inhibitor motif-containing protein 4 is a protein that in humans is encoded by the TMBIM4 gene. It is also known as human Golgi anti-apoptotic protein (hGAAP) due to its function and sub-cellular localization.
Human GAAP is a protein present in the Golgi that helps regulate apoptosis, a form of programmed cell death. By regulating the fluxes of Ca<sup>+2</sup>, an increase of GAAP can help prevent apoptosis. GAAP is also involved in promoting cell migration and has been identified as a novel Golgi cation channel. Other GAAPs can be found in all eucaryotes analyzed and in some bacteria. A viral GAAP (vGAAP) can also be found in some strains of vaccinia virus, the live vaccine used to eradicate smallpox.