PYCARD, often referred to as ASC (Apoptosis-associated speck-like protein containing a CARD), is a protein that in humans is encoded by the PYCARD gene. [5] It is localized mainly in the nucleus of monocytes and macrophages. In case of pathogen infection, however, it relocalizes rapidly to the cytoplasm, perinuclear space, endoplasmic reticulum and mitochondria and it is a key adaptor protein in activation of the inflammasome. [6]
NMR structure of full-length ASC: PDB ID 2KN6 [7]
This gene encodes an adaptor protein that is composed of two protein–protein interaction domains: a N-terminal PYRIN-PAAD-DAPIN domain (PYD) and a C-terminal caspase-recruitment domain (CARD). The PYD and CARD domains are members of the six-helix bundle death domain-fold superfamily that mediates assembly of large signaling complexes in the inflammatory and apoptotic signaling pathways via the activation of caspase. In normal cells, this protein is localized to the cytoplasm; however, in cells undergoing apoptosis, it forms ball-like aggregates near the nuclear periphery.
PYCARD can occur in four different isoforms. Isoform 1, often referred to as canonical PYCARD, and isoform 2 are the activatory isoforms. They co-localize with nucleotide oligomerization domain-like receptors (NLRs) and caspase-1. Unlike isoform 1, isoform 2 is involved in direct IL-1β processing regulation. Isoform 3 is an inhibitory isoform, so that it only co-localizes with caspase-1, but not with NLRs. Isoform 4 is not able to act as an adaptor protein in NLR signalling and its role remains elusive. [6]
Caspase recruitment domains, or caspase activation and recruitment domains (CARDs), are interaction motifs found in a wide array of proteins, typically those involved in processes relating to inflammation and apoptosis. These domains mediate the formation of larger protein complexes via direct interactions between individual CARDs. CARDs are found on a strikingly wide range of proteins, including helicases, kinases, mitochondrial proteins, caspases, and other cytoplasmic factors.
Caspase-1/Interleukin-1 converting enzyme (ICE) is an evolutionarily conserved enzyme that proteolytically cleaves other proteins, such as the precursors of the inflammatory cytokines interleukin 1β and interleukin 18 as well as the pyroptosis inducer Gasdermin D, into active mature peptides. It plays a central role in cell immunity as an inflammatory response initiator. Once activated through formation of an inflammasome complex, it initiates a proinflammatory response through the cleavage and thus activation of the two inflammatory cytokines, interleukin 1β (IL-1β) and interleukin 18 (IL-18) as well as pyroptosis, a programmed lytic cell death pathway, through cleavage of Gasdermin D. The two inflammatory cytokines activated by Caspase-1 are excreted from the cell to further induce the inflammatory response in neighboring cells.
NLR family pyrin domain containing 3 (NLRP3), is a protein that in humans is encoded by the NLRP3 gene located on the long arm of chromosome 1.
The BH3 interacting-domain death agonist, or BID, gene is a pro-apoptotic member of the Bcl-2 protein family. Bcl-2 family members share one or more of the four characteristic domains of homology entitled the Bcl-2 homology (BH) domains, and can form hetero- or homodimers. Bcl-2 proteins act as anti- or pro-apoptotic regulators that are involved in a wide variety of cellular activities.
Caspase 2 also known as CASP2 is an enzyme that, in humans, is encoded by the CASP2 gene. CASP2 orthologs have been identified in nearly all mammals for which complete genome data are available. Unique orthologs are also present in birds, lizards, lissamphibians, and teleosts.
Caspase-7, apoptosis-related cysteine peptidase, also known as CASP7, is a human protein encoded by the CASP7 gene. CASP7 orthologs have been identified in nearly all mammals for which complete genome data are available. Unique orthologs are also present in birds, lizards, lissamphibians, and teleosts.
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.
TNF receptor-associated factor 1 is a protein that in humans is encoded by the TRAF1 gene.
Caspase-10 is an enzyme that, in humans, is encoded by the CASP10 gene.
Calpain-2 catalytic subunit is a protein that in humans is encoded by the CAPN2 gene.
B-cell lymphoma/leukemia 10 is a protein that in humans is encoded by the BCL10 gene. Like BCL2, BCL3, BCL5, BCL6, BCL7A, and BCL9, it has clinical significance in lymphoma.
Receptor-interacting serine/threonine-protein kinase 2 is an enzyme that in humans is encoded by the RIPK2 gene.
NLRP1 encodes NACHT, LRR, FIIND, CARD domain and PYD domains-containing protein 1 in humans. NLRP1 was the first protein shown to form an inflammasome. NLRP1 is expressed by a variety of cell types, which are predominantly epithelial or hematopoietic. The expression is also seen within glandular epithelial structures including the lining of the small intestine, stomach, airway epithelia and in hairless or glabrous skin. NLRP1 polymorphisms are associated with skin extra-intestinal manifestations in CD. Its highest expression was detected in human skin, in psoriasis and in vitiligo. Polymorphisms of NLRP1 were found in lupus erythematosus and diabetes type 1. Variants of mouse NLRP1 were found to be activated upon N-terminal cleavage by the protease in anthrax lethal factor.
NACHT, LRR and PYD domains-containing protein 7 is a protein that in humans is encoded by the NLRP7 gene.
Nucleotide-binding oligomerization domain-like receptor (NLR) pyrin domain (PYD)-containing protein 12 is a protein that in humans is encoded by the NLRP12 gene.
NACHT, LRR and PYD domains-containing protein 4 is a protein that in humans is encoded by the NLRP4 gene.
The nucleotide-binding oligomerization domain-like receptors, or NOD-like receptors (NLRs), are intracellular sensors of pathogen-associated molecular patterns (PAMPs) that enter the cell via phagocytosis or pores, and damage-associated molecular patterns (DAMPs) that are associated with cell stress. They are types of pattern recognition receptors (PRRs), and play key roles in the regulation of innate immune response. NLRs can cooperate with toll-like receptors (TLRs) and regulate inflammatory and apoptotic response.
A pyrin domain is a protein domain and a subclass of protein motif known as the death fold, the 4th and most recently discovered member of the death domain superfamily (DDF). It was originally discovered in the pyrin protein, or marenostrin, encoded by MEFV. The mutation of the MEFV gene is the cause of the disease known as Familial Mediterranean Fever. The domain is encoded in 23 human proteins and at least 31 mouse genes.
NLRP10, short for NOD-like receptor family pyrin domain containing 10, is an intracellular protein of mammals that functions in apoptosis and the immune system. It is also known as NALP10, NOD8, PAN5, Pynod, and CLR11.1, and is one of 14 pyrin domain containing members of the NOD-like receptor family of cytoplasmic receptors, although it differs from other NOD-like receptors by lacking the characteristic leucine-rich repeat domain. It is also believed that it helps regulate the inflammatory response. NLRP10 reduces inflammatory and innate immune responses by inhibiting the activity of two proteins associated with the inflammasome; caspase-1 and PYCARD.
NOD-like receptor family pyrin domain containing 11 is a protein that in humans is encoded by the NLRP11 gene located on the long arm of human chromosome 19q13.42. NLRP11 belongs to the NALP subfamily, part of a large subfamily of CATERPILLER. It is also known as NALP11, PYPAF6, NOD17, PAN10, and CLR19.6
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