Cleaved-Caspase 4 (Gln81) Antibody - #AF5373

Inflammatory caspase. Essential effector of NLRP3 inflammasome-dependent CASP1 activation and IL1B and IL18 secretion in response to non-canonical activators, such as UVB radiation, cholera enterotoxin subunit B and cytosolic LPS. Independently of NLRP3 inflammasome and CASP1, promotes pyroptosis, through GSDMD cleavage and activation, and IL1A, IL18 and HMGB1 release in response to non-canonical inflammasome activators. Plays a crucial role in the restriction of Salmonella typhimurium replication in colonic epithelial cells during infection. In later stages of the infection, LPS from cytosolic Salmonella triggers CASP4 activation, which ultimately results in pyroptosis of infected cells and their extrusion into the gut lumen, as well as in IL18 secretion. Pyroptosis limits bacterial replication, while cytokine secretion promotes the recruitment and activation of immune cells and triggers mucosal inflammation. Involved in LPS-induced IL6 secretion; this activity may not require caspase enzymatic activity. Involved in cell death induced by endoplasmic reticulum stress and by treatment with cytotoxic APP peptides found Alzheimer's patient brains. Activated by direct binding to LPS without the need of an upstream sensor. Does not directly process IL1B. During non-canonical inflammasome activation, cuts CGAS and may play a role in the regulation of antiviral innate immune activation.

In response to activation signals, including endoplasmic reticulum stress or treatment with amyloid-beta A4 protein fragments (such as amyloid-beta protein 40), undergoes autoproteolytic cleavage.

Cytoplasm>Cytosol. Endoplasmic reticulum membrane>Peripheral membrane protein>Cytoplasmic side. Mitochondrion. Inflammasome. Secreted.
Note: Predominantly localizes to the endoplasmic reticulum (ER). Association with the ER membrane requires TMEM214 (PubMed:15123740). Released in the extracellular milieu by keratinocytes following UVB irradiation (PubMed:22246630).

Widely expressed, including in keratinocytes and colonic and small intestinal epithelial cells (at protein level). Not detected in brain.

Upon direct LPS-binding, forms large homooligomers, resulting in its activation. These oligomers are often referred to as 'non-canonical inflammasomes'. Active as a heterotetramer consisting of two anti-parallel arranged heterodimers, each one formed by a small and a large subunit (By similarity). In its precursor form, interacts with TMEM214; this interaction is required for association with the endoplasmic reticulum membrane. Interacts with CASP1. Interacts with NOD2. Interacts with SERPINB1; this interaction regulates CASP4 activity.

(Microbial infection) Interacts with NleF protein from pathogenic E.coli; this interaction leads to enzyme inhibition.

The CARD domain mediates LPS recognition and homooligomerization.

Belongs to the peptidase C14A family.