Negative regulator of amyloid-beta peptide production. May inhibit the processing of APP by blocking its access to alpha- and beta-secretase. Binding to the beta-secretase-cleaved APP C-terminal fragment is negligible, suggesting that ITM2C is a poor gamma-secretase cleavage inhibitor. May play a role in TNF-induced cell death and neuronal differentiation (By similarity). Interacts with BACE1. Interacts with APP. Interacts with STMN2. High levels in the brain, specifically in the cerebral cortex, medulla, amygdala, hippocampus, thalamus, caudate nucleus, cerebellum, olfactory lobe and spinal cord. Very low levels in other organs. Type I membrane-bound, as well as soluble, furin has a pre-eminent role in ITM2C proteolytic processing. PCSK7 and PCSK5 may also be involved although to a lesser extent. The soluble form of PCSK7 is incapable of processing ITM2C. Fails to undergo shedding by ADAM10 and intramembrane cleavage by SPPL2B. Belongs to the ITM2 family.