New Caspases’ inhibitors belonging to the serpin superfamily: A novel key control point of apoptosis in mammalian tissues

Abstract

The present report overviews a new family of bovine serpins able to inhibit pseudo-irreversibly initiator and effector caspases, a group of cysteine proteases in charge of cell dismantling during apoptosis, a finely regulated cell death process. The 8 members identified at the gene level showed a high homology with human SERPINA3 and were therefore designed bovSERPINA3-1 to A3-8. At least six of them are able to inhibit caspases. Two of them (bovSERPINA3-1 and A3-3) have been purified from bovine muscle and extensively investigated during these last years. After a general presentation of the serpin superfamily, the kinetic aspects of their interaction with human caspases 3 and 8 were studied and findings obtained suggest that caspases could be their target enzymes in living cells. In muscle and primary myoblast in culture, they showed an intracellular localization and because of their high level in blood, they can be exported. Two biological functions (potential regulator of apoptosis and expression during myoblast differentiation) were investigated and it was concluded that they are very likely an efficient regulator of apoptosis, a proposal supported by their high expression in proliferating myoblast (cell survival is essential during this differentiation phase) but not in myotubes.

Caspases and Thrombin Activity Regulation by Specific Serpin Inhibitors in Bovine Skeletal Muscle

“…The large number of genes encoding these serpins suggests a probable great complexity of the bovSERPINA3 subfamily of serpins. This complexity was supported by the two-dimensional gel electrophoresis of fractions F1 and F2 who showed multiple spots of glycosylated and phosphorylated proteins when revealed with a polyclonal antibody raised against purified bovSERPINA3-1 [27]. The high sequence homology between the identified members of the bovSERPINA3 family (>75 %) suggests that it exists a degree of compensation and redundancy between them comparable to the redundancy noted for caspases [25].…”

“…-Trypsin/elastase inhibitors BovSERPINA3-1 previously designed Endopin 1A [37,38,92,93] -Trypsin/thrombin inhibitor Antithrombin III [37] From the F2 fraction, we failed to purify to homogeneity any serine proteinase inhibitor probably because (1) most inhibitors of this fraction first shared very close structural and physicochemical properties with the F1 entities and (2) most of them are apparently common to F1 and F2 fractions according to their cross immuno-reactivity towards the antibody raised against bovSERPINA3-1 [27].…”

Theories concerning natural tenderization processes in post mortem meat

“…Okazały się one jednak nieprzydatne w przewidywaniu kruchości mięsa. W tym kontekście, jak wykazano w przypadku kalpain [63], proteaz cysteinowych [73] i kaspaz [21,82], bardziej odpowiednimi predyktorami kruchości (wspólnie lub pojedynczo) były parametry określane w chwili śmierci: proporcja enzym/inhibitor lub stężenie inhibitora aniżeli poziom docelowych enzymów (tab. 2).…”

“…Najlepszymi predyktorami kruchości mięsa (spośród analizowanych trzydziestu zmiennych ilościowych) okazały się inhibitory proteazy serynowej [82,83]. Ta nieoczekiwana właściwość była wyjątkowym zaskoczeniem, ponieważ nie stwierdzono, aby jakakolwiek proteaza serynowa brała udział w "rozluźnianiu" miofibryli [21,60].…”

“…Potwierdzono związek serpin (z grupy SERPINA3) hamujących aktywność kaspaz z kruchością mięsa [21,82]. Zidentyfikowanym inhibitorem trombiny jest enzym zlokalizowany na poziomie synaps mięśniowych, określony jako antytrombina III [26].…”