Functions as a protease inhibitor. Plays a role in APP processing regulating the physiological production of the beta amyloid peptide. Restricts docking of gamma-secretase to APP and access of alpha- and beta-secretase to their cleavage APP sequence.
Expressed in brain and in other tissues.
Defects in ITM2B are a cause of cerebral amyloid angiopathy ITM2B-related type 1 (CAA-ITM2B1) [MIM:176500]. A disorder characterized by amyloid deposition in the walls of cerebral blood vessels and neurodegeneration in the central nervous system. Cerebral amyloid angiopathy, non-neuritic and perivascular plaques and neurofibrillary tangles are the predominant pathological lesions. Clinical features include progressive mental deterioration, spasticity and muscular rigidity. Defects in ITM2B are a cause of cerebral amyloid angiopathy ITM2B-related type 2 (CAA-ITM2B2) [MIM:117300]; also known as heredopathia ophthalmo-oto-encephalica. A disorder characterized by amyloid deposition in the walls of the blood vessels of the cerebrum, choroid plexus, cerebellum, spinal cord and retina. Plaques and neurofibrillary tangles are observed in the hippocampus. Clinical features include progressive ataxia, dementia, cataracts and deafness.
Belongs to the ITM2 family. Contains 1 BRICHOS domain.
The C-terminal part of the ectodomain is processed by furin and related proteases producing a secreted peptide of 4 to 5 kDa. For the ABRI and ADAN variants the C-terminal secreted peptide is larger and may produce amyloid fibrils responsible for neuronal dysfunction and dementia. The remaining part of the ectodomain containing the BRICHOS domain is cleaved by ADAM10 and is secreted as a peptide of 25 kDa. The membrane-bound N-terminal fragment (NTF) of 22 kDa is further proteolytically processed by SPPL2A and SPPL2B through regulated intramembrane proteolysis producing a secreted peptide (BRI2C) and an intracellular domain (ICD) released in the cytosol.