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Tissue-autonomous immune response regulates stress signalling during hypertrophy

ABSTRACT: Postmitotic tissues are incapable of replacing damaged cells through proliferation, but need to rely on buffering mechanisms to prevent tissue disintegration. By constitutively activating the Ras/MAPK-pathway via RasV12-overexpression in the postmitotic salivary glands of Drosophila larvae, we overrode the glands adaptability to growth signals, induced hypertrophy and stress accumulation. This allowed us to decipher a novel, spatio-temporally regulated interaction between the JNK-stress response and a genuine tissue-autonomous immune response. Central to this interaction is the direct inhibition of JNK-signalling by the antimicrobial peptide Drosomycin, which blocks programmed cell death and prevents recognition of the stressed tissue by the systemic immune response. While this mechanism might allow growing salivary glands to cope with temporary stress, continuous expression of Drosomycin favors survival of unrestricted, hypertrophic RasV12-glands. Our findings indicate the necessity for refined therapeutic approaches that fundamentally acknowledge detrimental effects that stimulated immune responses have on tissues coping with damage and stress.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE138936 | GEO | 2020/12/30

REPOSITORIES: GEO

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Project description:The early stages of the immune response against aberrant tissues such a tumors are technically difficult to study and therefore little understood. To analyze the innate immune response towards modified self-tissue we expressed a dominant-active version of the Ras oncogene in Drosophila imaginal discs and salivary glands. Signs of an immune response are observed on wings of adult flies, which show spots of melanization and in larvae, where the salivary glands attract blood cells. In line with the strong response mounted against salivary glands, they are found to express metalloproteases and apoptotic markers making them both accessible and recognizable for the immune system. The response against the glands bears several hallmarks of an encapsulation response including flattening of plasmatocytes, differentiation of lamellocytes, attachment of crystal cells and melanization at the final stage. RNA sequencing of the fat body, the primary producer of immune effectors, reveals a pattern of induced genes, which overlaps the one previously found upon wasp infestation but shows also several specific features. Evidence for the functional importance of one of the induced genes is presented proving the power of our approach to identify regulators of the response against modified self. Transcriptome analysis of the immune response in the fat body after expression of dominant-active RAS in the wing imaginal discs and salivary glands. Comparison of fat bodies from 3 control and 3 RAS-expressing larvae. For each sample fat bodies from 40 individuals were dissected. Differential gene expression files [output of Cuffdiff] are linked below: ResultsContr123vsRas123Individual.xls: Output file of Cuffdiff. Differential gene expression analysis, three control compared to individual Ras induced; replicate analysis using Cuffdiff. ResultsContr123vsRas123Multiple.xls: Output file of Cuffdiff. Differential gene expression analysis, three control compared to three Ras induced; replicate analysis using Cuffdiff. ResultsContr123vsRas12Multiple.xls: Output file of Cuffdiff. Differential gene expression analysis, three control compared to two Ras induced; replicate analysis using Cuffdiff.

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Tissue-autonomous immune response regulates stress signalling during hypertrophy

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