FEM1B: Proteins and Enzymes

Fas and tumor necrosis factor receptor 1 (TNFR1) are two prototype members in the death receptor family. A novel protein that associates with the intracellular domains of Fas and TNFR1 was recently identified and designated F1Aa and FEM1b (1,2). F1Aa/FEM1b is the homologue of C. elegans sex determining protein FEM-1. FEM-1/F1Aa is cleaved by CED-3 and caspase (3). FEM-1/F1Aa associates with CED-4 and its mammalian homologue Apaf-1 (3). Overexpression of F1Aa induces apoptosis. F1Aa is therefore a novel member of the death receptor associated protein that mediates apoptosis. F1Aa is expressed in a variety of human and mouse tissues.