Intramembrane-cleaving aspartic protease (I-CLiP) that cleaves type II membrane signal peptides in the hydrophobic plane of the membrane. Functions in ITM2B and TNF processing (PubMed:16829951, PubMed:16829952, PubMed:17965014, PubMed:19114711, PubMed:22194595). Catalyzes the intramembrane cleavage of the anchored fragment of shed TNF (TNF), which promotes the release of the intracellular domain (ICD) for signaling to the nucleus (PubMed:16829951, PubMed:16829952). May play a role in the regulation of innate and adaptive immunity (PubMed:16829952). Catalyzes the intramembrane cleavage of the simian foamy virus processed leader peptide gp18 of the envelope glycoprotein gp130 dependently of prior ectodomain shedding by furin or furin-like proprotein convertase (PC)-mediated cleavage proteolysis (PubMed:23132852). {ECO:0000269|PubMed:16829951, ECO:0000269|PubMed:16829952, ECO:0000269|PubMed:17965014, ECO:0000269|PubMed:19114711, ECO:0000269|PubMed:22194595, ECO:0000269|PubMed:23132852}. This is the function of SPPL2B (signal peptide peptidase like 2B, ENSG00000005206).