Caspases are endoproteases that play important roles in the regulation of cell death and apoptosis. Caspase active sites contain a catalytic cysteine residue essential for the proteolytic cleavage of their substrates at conserved aspartic acid residues (1). Caspases are produced as inactive procaspase monomers in order to regulate their activity. Upon dimerization procaspases are cleaved to produce their active form (1). Caspases are typically grouped by their role in either cell death or inflammation. Inflammatory caspases (caspase-1, -4, -5, -12) are important mediators of the innate immune response. Inflammatory procaspases are activated by the inflammasome, a multiprotein complex formed in response to stimulation of pattern-recognition receptors by pathogen derived molecules such as LPS (1). Activated caspases are then able to facilitate the activation and secretion of inflammatory cytokines (1). Although the precise function of caspase-5 is unclear, its expression appears to be induced by LPS and is a member of inflammasome complexes necessary for the production of mature interleukin-1β (2).
Caspase-5 antibodies have been used to identify components of inflammasome complexes. For example, Agostini et al. performed immmunoprecipitation experiments to examine the proteins associated with the NALP3 inflammasome (3). The Elner group at the University of Michigan investigated the inflammatory roles of caspase-5 in human retinal pigment epithelial cells (4). Their experiments showed induction of caspase-5 by LPS at the mRNA level through RT-PCR and at the protein level through western blotting with a caspase-5 antibody (4). Additionally, they were able to use the caspase-5 antibody to monitor caspase-5 activation by comparing levels of procaspase-5 and cleaved caspase-5. Caspse-5 antibodies may serve as a good tool for monitoring inflammation and has been used in various situations ranging from psoriasis to lung cancer. In one study by Carter et al., researchers identified caspase-5 as being highly upregulated in rats exposed to cigarette smoke (5). Western blotting with the caspase-5 antibody showed increased protein levels along with other proteins involved in apoptosis, inflammation, and cell stress response (5).
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