The Death Domain of Kidney Ankyrin Interacts with Fas and Promotes Fas-Mediated Cell Death in Renal Epithelia

Ankyrins are a ubiquitously expressed family of conserved proteins that mediate the linkage of integral membrane proteins such as transporters and channels with the underlying cytoskeleton. Ankyrins possess a conserved death domain, the functional significance of which has remained puzzling. In this study, the death domain of AnkG190, the isoform of ankyrin expressed in kidney tubules, was used as bait in a yeast two-hybrid screen to identify interacting partners. One of these interactions was with the proapoptotic molecule Fas. This was confirmed by coimmunoprecipitation, colocalization, and glutathione S-transferase pull-down assays in cultured renal epithelial (MDCK) cells. Site-directed mutagenesis of a conserved arginine (R1496 in AnkG190), previously shown to be critical for the binding of Fas (R234 in Fas) to FADD, abolished the interaction of ankyrin's death domain with Fas. Overexpression of constructs containing ankyrin's death domain promoted Fas-mediated apoptosis in MDCK cells. The linkage between ankyrin and Fas was confirmed in vivo in mouse kidney tubule cells by coimmunoprecipitation and colocalization. In an established mouse model of renal ischemia-reperfusion injury characterized by apoptotic tubule cell death, the expression of both ankyrin and Fas was markedly induced, and the interaction between these molecules remained intact. The results identify a novel tethering interaction between ankyrin and Fas in kidney epithelia and suggest that AnkG190 may play a role as an adapter molecule in renal tubule cell death.