In molecular biology, the Signal Peptide Peptidase (SPP) is a type of protein that specifically cleaves parts of other proteins. It is an intramembrane aspartyl protease with the conserved active site motifs 'YD' and 'GxGD' in adjacent transmembrane domains (TMDs). Its sequences is highly conserved in different vertebrate species. SPP cleaves remnant signal peptides left behind in membrane by the action of signal peptidase and also plays key roles in immune surveillance and the maturation of certain viral proteins.
Gamma secretase is a multi-subunit protease complex, itself an integral membrane protein, that cleaves single-pass transmembrane proteins at residues within the transmembrane domain. Proteases of this type are known as intramembrane proteases. The most well-known substrate of gamma secretase is amyloid precursor protein, a large integral membrane protein that, when cleaved by both gamma and beta secretase, produces a short 37-43 amino acid peptide called amyloid beta whose abnormally folded fibrillar form is the primary component of amyloid plaques found in the brains of Alzheimer's disease patients. Gamma secretase is also critical in the related processing of several other type I integral membrane proteins, such as Notch, ErbB4, E-cadherin, N-cadherin, ephrin-B2, or CD44.
Presenilins are a family of related multi-pass transmembrane proteins which constitute the catalytic subunits of the gamma-secretase intramembrane protease protein complex. They were first identified in screens for mutations causing early onset forms of familial Alzheimer's disease by Peter St George-Hyslop. Vertebrates have two presenilin genes, called PSEN1 that codes for presenilin 1 (PS-1) and PSEN2 that codes for presenilin 2 (PS-2). Both genes show conservation between species, with little difference between rat and human presenilins. The nematode worm C. elegans has two genes that resemble the presenilins and appear to be functionally similar, sel-12 and hop-1.
Presenilin-1(PS-1) is a presenilin protein that in humans is encoded by the PSEN1 gene. Presenilin-1 is one of the four core proteins in the gamma secretase complex, which is considered to play an important role in generation of amyloid beta (Aβ) from amyloid-beta precursor protein (APP). Accumulation of amyloid beta is associated with the onset of Alzheimer's disease.
Caspase-6 is an enzyme that in humans is encoded by the CASP6 gene. CASP6 orthologs have been identified in numerous mammals for which complete genome data are available. Unique orthologs are also present in birds, lizards, lissamphibians, and teleosts. Caspase-6 has known functions in apoptosis, early immune response and neurodegeneration in Huntington's and Alzheimer's disease.
Presenilin-2 is a protein that is encoded by the PSEN2 gene.
Dynamin-like 120 kDa protein, mitochondrial is a protein that in humans is encoded by the OPA1 gene. This protein regulates mitochondrial fusion and cristae structure in the inner mitochondrial membrane (IMM) and contributes to ATP synthesis and apoptosis, and small, round mitochondria. Mutations in this gene have been implicated in dominant optic atrophy (DOA), leading to loss in vision, hearing, muscle contraction, and related dysfunctions.
Serine protease HTRA2, mitochondrial is an enzyme that in humans is encoded by the HTRA2 gene. This protein is involved in caspase-dependent apoptosis and in Parkinson's disease.
Minor histocompatibility antigen H13 is a protein that in humans is encoded by the HM13 gene.
Mitochondrial fission 1 protein (FIS1) is a protein that in humans is encoded by the FIS1 gene on chromosome 7. This protein is a component of a mitochondrial complex, the ARCosome, that promotes mitochondrial fission. Its role in mitochondrial fission thus implicates it in the regulation of mitochondrial morphology, the cell cycle, and apoptosis. By extension, the protein is involved in associated diseases, including neurodegenerative diseases and cancers.
Signal peptide peptidase-like 2B, also known as SPPL2B, is a human gene.
Signal peptide peptidase-like 2A, also known as SPPL2A, is a human gene.
Mitochondrial carrier homolog 1 (MTCH1), also referred to as presenilin 1-associated protein (PSAP), is a protein that in humans is encoded by the MTCH1 gene on chromosome 6. MTCH1 is a proapoptotic mitochondrial protein potentially involved in Alzheimer’s disease (AD).
ATP-dependent metalloprotease YME1L1 is an enzyme that in humans is encoded by the YME1L1 gene. YME1L1 belongs to the AAA family of ATPases and mainly functions in the maintenance of mitochondrial morphology. Mutations in this gene would cause infantile-onset mitochondriopathy.
Howel–Evans syndrome is an extremely rare condition involving thickening of the skin in the palms of the hands and the soles of the feet (hyperkeratosis). This familial disease is associated with a high lifetime risk of esophageal cancer. For this reason, it is sometimes known as tylosis with oesophageal cancer (TOC).
The rhomboid proteases are a family of enzymes that exist in almost all species. They are proteases: they cut the polypeptide chain of other proteins. This proteolytic cleavage is irreversible in cells, and an important type of cellular regulation. Although proteases are one of the earliest and best studied class of enzyme, rhomboids belong to a much more recently discovered type: the intramembrane proteases. What is unique about intramembrane proteases is that their active sites are buried in the lipid bilayer of cell membranes, and they cleave other transmembrane proteins within their transmembrane domains. About 30% of all proteins have transmembrane domains, and their regulated processing often has major biological consequences. Accordingly, rhomboids regulate many important cellular processes, and may be involved in a wide range of human diseases.
Intramembrane proteases (IMPs), also known as intramembrane-cleaving proteases (I-CLiPs), are enzymes that have the property of cleaving transmembrane domains of integral membrane proteins. All known intramembrane proteases are themselves integral membrane proteins with multiple transmembrane domains, and they have their active sites buried within the lipid bilayer of cellular membranes. Intramembrane proteases are responsible for proteolytic cleavage in the cell signaling process known as regulated intramembrane proteolysis (RIP).
Rhomboid-related protein 2 is a protein that in humans is encoded by the RHBDL2 gene.
Metalloendopeptidase OMA1, mitochondrial is an enzyme that in humans is encoded by the OMA1 gene. OMA1 is a Zn2+-dependent metalloendopeptidase in the inner membrane of mitochondria. The OMA1 acronym was derived from overlapping proteolytic activity with m-AAA protease 1.
Glucokinase regulator is a protein that in humans is encoded by the GCKR gene.
