Disease:Defects in PSEN2 are the cause of Alzheimer disease type 4 (AD4) [MIM:606889]. AD is an autosomal dominant Alzheimer disease. Alzheimer disease is a neurodegenerative disorder characterized by progressive dementia , loss of cognitive abilities , and deposition of fibrillar amyloid proteins as intraneuronal neurofibrillary tangles , extracellular amyloid plaques and vascular amyloid deposits. The major constituent of these plaques is the neurotoxic amyloid-beta-APP 40-42 peptide (s) , derived proteolytically from the transmembrane precursor protein APP by sequential secretase processing. The cytotoxic C-terminal fragments (CTFs) and the caspase-cleaved products such as C31 derived from APP , are also implicated in neuronal death. ,Disease:Three causative genes have been identified that when mutated lead to presenile Alzheimer Disease: APP (amyloid precursor protein gene) , PSEN1 and PSEN2. These three genes account for half of the families with autosomal dominant presenile AD , which represent approximately 10% of the whole AD population. In addition , apolipoprotein E has been identified as a risk-modifying locus. ,Domain:The PAL motif is required for normal active site conformation. ,Function:Probable catalytic subunit of the gamma-secretase complex , an endoprotease complex that catalyzes the intramembrane cleavage of integral membrane proteins such as Notch receptors and APP (beta-amyloid precursor protein) . Requires the other members of the gamma-secretase complex to have a protease activity. May play a role in intracellular signaling and gene expression or in linking chromatin to the nuclear membrane. May function in the cytoplasmic partitioning of proteins. ,online information:Presenilins mutations ,PTM:Heterogeneous proteolytic processing generates N-terminal and C-terminal fragments. ,PTM:Phosphorylated on serine residues. ,similarity:Belongs to the peptidase A22A family. ,subunit:Interacts with DOCK3 (By similarity) . Homodimer. Component of the gamma-secretase complex , a complex composed of a presenilin homodimer (PSEN1 or PSEN2) , nicastrin (NCSTN) , APH1 (APH1A or APH1B) and PEN2. Such minimal complex is sufficient for secretase activity , although other components may exist. Interacts with HERPUD1 , FLNA , FLNB and PARL. ,tissue specificity:Isoform 1 is seen in the placenta , skeletal muscle and heart while isoform 2 is seen in the heart , brain , placenta , liver , skeletal muscle and kidney. ,
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