Tight junction-associated protein that is involved in the survival of auditory hair cells and hearing. Maybe by modulating the barrier properties and mechanical stability of tight junctions (By similarity). Has no peptidase activity (PubMed:14715245). Interacts (via the C-terminal region) with the heterodimer TJP1:TJP2. Expressed predominantly in skeletal muscle and heart. Belongs to the peptidase C19 family. Although the active site residues are conserved, lacks the conserved His residue which is normally found 9 residues before the catalytic His. Truncated N-terminus.