Interactions of cellular polypeptides with the cytoplasmic domain of the mouse Fas antigen. 
The mouse Fas/APO-1 antigen represents a 45-kilodalton transmembrane receptor that initiates apoptosis by a poorly defined signaling mechanism.  The cytoplasmic domain of Fas does not display any known enzymatic activities but is capable of interacting with a number of proteins that were identified recently using the yeast interactive cloning method.  To investigate direct biochemical interactions from cellular lysates prepared from Fas-responsive cells, a series of recombinant glutathione S-transferase-mouse Fas fusion proteins representing different regions of the mouse Fas cytoplasmic domain was used.  Polypeptides of 25, 50, and 70 kilodaltons were found to associate with the Fas intracellular domain, and this binding was stable in the presence of 1 M NaCl.  These interactions were also detected using a mouse Fas fusion protein containing an Ile to Asn mutation, which is responsible for a lymphoproliferative disorder in certain strains of mice (lprcg).  Furthermore, the binding of cellular proteins to Fas could be blocked upon incubation with a polyclonal antibody directed against the cytoplasmic domain of Fas.  The strong association of cellular proteins with the cytoplasmic region implies that constitutive interactions may exist to regulate apoptotic signaling through the Fas antigen.