CASP is a small cytokine-inducible protein, primarily expressed in hematopoetic 
cells, which associates with members of the Cytohesin/ARNO family of guanine 
nucleotide-exchange factors. Cytohesins activate ARFs, a group of GTPases 
involved in vesicular initiation. Functionally, CASP is an adaptor protein 
containing a PDZ domain, a coiled-coil, and a potential carboxy terminal 
PDZ-binding motif that we sought to characterize here. Using GST pulldowns and 
mass spectrometry we identified the novel interaction of CASP and sorting nexin 
27 (SNX27). In lymphocytes, CASP's PDZ-binding motif interacts with the PDZ 
domain of SNX27. This protein is a unique member of the sorting nexin family of 
proteins, a group generally involved in the endocytic and intracellular sorting 
machinery. Endogenous SNX27 and CASP co-localize at the early endosomal 
compartment in lymphocytes and also in transfection studies. These results 
suggest that endosomal SNX27 may recruit CASP to orchestrate intracellular 
trafficking and/or signaling complexes.