Expression, tissue distribution, and cellular localization of the antiapoptotic TIP-B1 protein

TIP-B1 is a novel 27-kDa protein isolated from the cytosol of tumor necrosi s factor (TNF)-stimulated cells. Cells preincubated with TIP-B1 are protect ed from TNF-induced apoptosis. This study showed that, as with normal fibro blasts and U937 histiocytic lymphoma, human MCF? mammary adenocarcinoma cel ls were protected from TNF in a concentration-dependent manner by pretreatm ent with either TNF or purified TIP-B1. Immunoblot and immunohistochemical analyses indicated expression of both TIP-B1 mRNA and protein in MCF7 cells and heart, kidney, brain, liver, ovary, uterus, thymus, spleen, lymph node , and mammary gland cells throughout their development. Expression of TIP-B 1 was heterogeneous, with staining of specific cell types within tissues. B ased on the ability of TIP-B1 to protect both normal and turner cells from TNF-induced apoptosis and its broad tissue distribution, with expression on ly in select cells within those tissues, a role for TIP-B1 in the regulatio n of TNF-induced effects is strongly indicated.