Is an ortholog of human STAM (signal transducing adaptor molecule) and STAM2 (signal transducing adaptor molecule 2). Exhibits protein C-terminus binding activity and ubiquitin binding activity. Is involved in several processes, including endosome to lysosome transport\; ephrin receptor signaling pathway\; and negative regulation of MAPK cascade. Localizes to the ESCRT-0 complex\; cilium\; and early endosome. Is expressed in the male gonad\; the nervous system\; and the pharyngeal-intestinal valve.