Identification And Functional Study Of Caspases In Aedes Albopictus

Apoptosis is a type of programmed cell death that plays a vital role in immunity, development, and tissue homeostasis. The key mediators of apoptosis are caspases. Caspases (cysteine-containing aspartate-specific proteases) are synthesized as inactive proenzymes containing a prodomain, a large subunit (P20) and a small subunit (P10). They are typically classified into initiator and effector caspases depending on the length of the prodomain.Aedes albopictus mosquito is a vector of various arboviruses and is becoming a significant threat to public health due to its rapid global expansion. Several reports suggest that apoptosis could be a factor limiting arbovirus infection in mosquitoes. Thus, it is significant to identify apoptosis pathway in Aedes albopictus.This study identified 5 caspases:Aedes albopictus drone (Aadronc), Aedes albopictus casps7 (AacaspsT), Aedes albopictus casps8 (Aacasps8), Aedes albopictus caspsl9 (Aacaspsl9) and Aedes albopictus casps20 (Aacasps20). All the caspases showed the characteristics of caspases. According to phylogenetic analysis, AaDronc belonged to initiator caspases, and AaCASPS7, AaCASPS8, AaCASPS19, AaCASPS20 were classified as effector caspases.Aacasps7, Aacasps8, Aadronc and Aacasps20 transcripts were expressed ubiquitously in developmental stages and adults in Aedes albopictus mosquitoes.AaDronc had the highest activity against to the initiator caspase substrates Ac-IETD-AFC. While AaCASPS7 and AaCASPS20 exhibited significant activity to effector caspase substrates. AaCASPS19 cleaved not only the effector caspase substrates, but also the initiator caspase substrates. The active site mutation of the caspases led to complete loss of activities to all the substrates tested. Futhermore, AaCASPS7 could be cleaved by AaDronc.Transient expression of AaDronc or AaCASPS7 induced apoptosis in C6/36 cells. More apoptotic bodies were observed in C6/36 cells transiently co-expressing AaDronc and AaCASPS7 than in C6/36 cells transiently AaDronc or AaCASPS7 alone.This study initially described the genetic and biochemical characterization of five caspases in Aedes albopictus. Our characterization of these genes will help elucidate the molecular mechanisms of apoptosis regulation in Aedes albopictus.