SPPL3 (Signal Peptide Peptidase-Like 3) is an enzyme belonging to the intramembrane-cleaving protease family that processes specific transmembrane proteins. By releasing intracellular domains from its substrates, SPPL3 affects cellular signaling and regulation. It plays a crucial role in immune system function, including B cell maturation, and has been associated with certain autoimmune diseases. Research on SPPL3 helps to uncover how intramembrane proteolysis influences human health and disease.