Disease relevance of CrmA

• Cowpox virus (CPV) expresses the serpin (serine proteinase inhibitor) CrmA, an anti-inflammatory, anti-apoptotic protein required for production of red pocks on chicken chorioallantoic membranes (CAMs) [1].
• Cowpox virus CrmA, Myxoma virus SERP2 and baculovirus P35 are not functionally interchangeable caspase inhibitors in poxvirus infections [1].
• Activation of caspases in pig kidney cells infected with wild-type and CrmA/SPI-2 mutants of cowpox and rabbitpox viruses [2].
• In contrast, XIAP, cowpox virus CrmA and baculovirus p35 inhibited TRAIL-induced apoptosis [3].
• When five myc epitopes were attached to vaccinia virus protein CrmA, its signal was multiplied 5.8 times in Western blot analysis, compared with that of one epitope-tagged CrmA [4].

High impact information on CrmA

• Tumor necrosis factor-induced apoptosis is mediated by a CrmA-sensitive cell death pathway [5].
• The cowpox virus CrmA protein, a member of the serpin superfamily, inhibits the enzymatic activity of ICE and ICE-mediated apoptosis [5].
• We have compared the kinetics of interaction of CrmA with five proteases that may play a role in apoptosis [6].
• The only reported target for the CrmA protein is the cysteine protease interleukin-1 beta converting enzyme (ICE) [7].
• Thus the mechanism of CrmA involves the unusual ability to efficiently inhibit proteinases from two distinct catalytic classes, in this case serine and cysteine proteinases [8].

Chemical compound and disease context of CrmA

• CrmA (a serpin from cowpox virus) and zVAD-FMK (N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone) inhibited Sindbis virus-induced cell death, suggesting that cellular caspases facilitate apoptosis induced by Sindbis virus [9].
• Human T leukemic cells engineered to overexpress the cowpox virus CrmA protein, a direct and specific inhibitor of caspase proteases, were studied for their resistance to 1-beta-D-arabinofurasosyl-cytosine (Ara-C), etoposide (VP-16), doxorubicin (DOX), and cis-dichlorodiammine platinum (CP) [10].
• Overexpression of baculovirus protein p35 blocked ceramide-induced DNA fragmentation and proteolytic activity, whereas overexpression of cowpox virus protein CrmA had no effect on these events [11].

Biological context of CrmA

• These results suggest that the RPV SPI-2 and CPV CrmA proteins are not functionally equivalent and that CrmA, but not SPI-2 protein, can completely prevent apoptosis in LLC-PK1 cells under these conditions [2].
• Serp2 and CrmA both contain Asp at the P1 position within the serpin reactive site loop and yet are only 35% identical overall [12].
• Subcellular localization of CrmA: identification of a novel leucine-rich nuclear export signal conserved in anti-apoptotic serpins [13].
• CrmA thus represents the first example of a viral gene product capable of directly blocking CTL-mediated cell death [14].
• CrmA also failed to block DNA fragmentation and loss of cell viability [15].

Anatomical context of CrmA

• Thus, through CrmA, the virus may influence two of the pathways normally used to kill virus-infected cells: acting on endogenous proteinases such as ICE and on exogenous proteinases delivered by cytotoxic lymphocytes to infected cells [8].
• Mixed infection of LLC-PK1 cells with wt RPV and wt CPV gave no PARP-cleaving activity, and all PARP cleavage mediated by SPI-2 and CrmA mutants of RPV and CPV, respectively, could be eliminated by coinfection with wt CPV [2].
• In addition, overexpression of the cowpox virus protein CrmA, a molecule with inhibitory potential on caspase-1 and caspase-8, specifically involved in Fas-induced signaling, protected T cells from being destroyed by the neoplastic cells or the agonistic anti-Fas MoAb [16].
• In U937 cells exposed to TPA, these proteolytic events can be inhibited by expression of a caspase-8 dominant negative mutant or the cowpox virus CrmA caspase inhibitor [17].
• IL-3 withdrawal activates a CrmA-insensitive poly(ADP-ribose) polymerase cleavage enzyme in factor-dependent myeloid progenitor cells [15].

Associations of CrmA with chemical compounds

• Altering the critical P1-aspartate in the CrmA reactive centre loop to alanine resulted in a virus (CPV-CrmA-D303A) that resembled CPV deleted for CrmA (CPVDeltaCrmA : : lacZ); on CAMs it produced white, inflammatory pocks with activated caspase-3 and reduced virus yields, suggesting that CrmA activities are mediated via proteinase inhibition [1].
• Previously we have shown CrmA to be an inhibitor of the cysteine proteinase interleukin-1 beta-converting enzyme (ICE) [8].
• In addition to CrmA, a tripeptide caspase-protease inhibitor, z-Val-Ala-Asp-fluoromethylketone could also suppress TGF-beta-induced apoptosis in a dose-dependent manner [18].
• Although such cells were completely resistant to apoptosis induced by antibodies to the Apo-1/Fas surface receptor (a form of apoptosis known to be inhibitable by CrmA), they were not protected from ceramide-induced cell death [19].

Analytical, diagnostic and therapeutic context of CrmA

• These results indicate that CrmA is an effective gene product for inhibiting Fas/FasL-mediated apoptosis, which suggests the potential therapeutic use of its gene transduction to protect against graft damage due to delayed and/or chronic xenograft rejection [20].
• These data suggested that FasL and CrmA may be potent genes to prolong rat liver allograft survival [21].
• Using the high responder rat combination of DA (RT-1(a)) donor to LEW (RT-1(1)) recipient, we performed orthotopic liver transplantation with subsequent delivery of adenoviral vectors containing FasL, CrmA, or LacZ, at a dose of 1 x 10(9) pfu via a recipient tail vein using a Cre-mediated gene expression system [21].

References