Rel Related Proteins and MAP Kinase p38 in Regulating Drosophila Immunity: a Dissertation

Abstract

NF-кB/Rel family proteins regulate genes that are critical for many cellular processes including apoptosis, inflammation, immune response, as well as development. NF-кB/Rel proteins function as homodimers or heterodimers, which recognize specific DNA sequences within target promoters. I examined the activity of different Drosophila Rel-related proteins in modulating Drosophila immunity genes by expressing the Rel proteins in stably transfected cell lines. I also compared how different combinations of these transcriptional regulators control the activity of various immunity genes. The results show that Rel proteins are directly involved in regulating the Drosophila antimicrobial response. Furthermore, expression of drosomycin and defensin is best induced by the Relish/Dif and the Relish/Dorsal heterodimers, respectively; whereas attacin activity can be efficiently up-regulated by the Relish homodimer and heterodimers. These results illustrate how the formation of Rel protein dimers differentially regulates target gene expression. Another area of my research is to investigate the function of p38 MAP kinase (mitogen-activated protein kinase) in Drosophila immune response. In vertebrates, one of the responses evoked by the pro-inflammatory cytokines and lipopolysaccharide (LPS) is the initiation of a kinase cascade that leads to the phosphorylation of p38 MAP kinase on Thr and Tyr within the motif Thr-Gly-Tyr, which is located within subdomain VIII. Two genes that are highly homologous to the mammalian p38 MAP kinases were molecularly cloned and characterized. Furthermore, genes that encode two novel Drosophila MAP kinase kinases, D-MKK3 and D-MKK4, were identified. D-MKK3 is an efficient activator of both Drosophila p38 MAP kinases, while D-MKK4 is an activator of D-JNK but not D-p38. These data establish that Drosophila indeed possesses a conserved p38 MAP kinase signaling pathway. We have examined the role of the D-p38 MAP kinases in the regulation of insect immunity. The results revealed that one of the functions of D-p38 is to attenuate antimicrobial peptide gene expression induced by LPS.