Immune signalling in insect cells

Immune responses in insects include components and mechanisms that are highly evolutionarily conserved. In addition to providing insight into the insects themselves, knowledge of the conserved mechanisms involved in insect immunity can offer valuable insight that is broadly relevant to a wide variety of other species. Three aspects of insect immune cell signalling have been studied here. Cell signalling responses have been investigated in two insect cell lines following treatment with double stranded (ds) RNA, a common intermediate of viral replication. It has been established that both cell lines investigated, from the fruitfly Drosophila melanogaster and vector mosquito Aedes albopictus, do not exhibit adivation of mitogen activated protein kinases (MAPKs) or NF-KB proteiris as a direct response to dsRNA. Secondly, a detailed analysis of the mechanisms of transcriptional regulation has been carried out on the Drosophila drosomycin gene, a key factor both in terms of its function during the immune response and in terms of its role during previous characterisation of Drosophila immune signalling. The drosomycin promoter was found to be regulated independently by the Toll and IMD signalling pathways via distinct sequence elements. Finally, investigation of the responses of an A. albopictus cell line to treatment with bacterial cell wall components has revealed key differences in the mechanisms involved in immune-induced regulation of transcription compared with the model established in Drosophila. A role for p38 MAPK has been identified in the negative regulation of transcription of A. albopictus cecropin A1, an inducible antimicrobial peptide gene.