| Binding of the intracellular Fas ligand ( FasL ) domain to the adaptor protein PSTPIP results in a cytoplasmic localization of FasL . ^^^ PSTPIP co expression leads to an increased intracellular localization of Fas ligand , thereby regulating extracellular availability and cytotoxic activity of the molecule . ^^^ Here we report the identification of the Src homology 3 domain containing adaptor protein PSTPIP as a FasL interacting partner , which binds to the proline rich domain . ^^^ In addition , we demonstrate recruitment of the tyrosine phosphatase PTP PEST by PSTPIP into FasL . ^^^ |