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. 2018 Apr 3;7(4):bio029454. doi: 10.1242/bio.029454

Fig. 8.

Fig. 8.

Activin signaling regulates the life span of adult fruit flies by modulating the function of proteasome in adult fruit fly muscle tissues. (A) Western blot data for the protein levels of a 26S proteasome catalytic α subunit from 1-week-old adult thoracic muscle and larval body wall muscle of different genotype fruit flies. (B) Quantification results of the western blot data from A. (C) Knocking down the transcripts of Prosβ5 gene in adult fruit fly muscle with a UAS-Pros β5 RNAi line (Bloomington stock number 53974) and a TubGal80ts; MhcGal4 driver line resulted in shortened mean lifespan of the experimental fruit flies when compared to the control fruit flies (P<0.05). Blue curve: survivorship of Mhc-Gal4/UAS-Prosβ5 RNAi flies. Red curve: survivorship of UAS- Prosβ5 RNAi/yw control flies. Green curve: survivorship of Mhc-Gal4/v1 control flies. (D) Co-expression of a proteasome RNAi transgene UAS-Rpn1 RNAi together with wild-type Myo in adult muscle has abolished the lifespan extension effect of Myo. The lifespan extension effect of Myo shown in Fig. 4C and D is not seen any more here when both UAS-Rpn1 RNAi and UAS-Myo were activated by MhcGal4 in adult muscle tissues (blue curve versus green, cyan, and dark purple curves). Green curve: survivorship of UAS-Rpn1 RNAi/yw flies. Cyan curve: survivorship of UAS-Rpn1 RNAi, UAS-Myo/yw flies. Dark purple curve: survivorship of MhcGal4/137 control flies. (E) Expression of an Rpn1 RNAi in adult fruit fly muscle severely compromised the lifespan extension effect by the over-expression of a wild-type Daw gene in adult muscle (blue curve versus the blue curves in Fig. 7A and B). Blue curve: survivorship of TubGal80ts, Mhc-Gal4/UAS-Rpn1 RNAi, UAS-Daw flies. Red curve: survivorship of TubGal80ts, Mhc-Gal4/UAS-Rpn1 RNAi flies. Green curve: survivorship of UAS-Rpn1 RNAi, UAS-Daw/yw flies. The survivorship of the control TubGal80ts, Mhc-Gal4/137 flies is not shown here, but can be seen as the magenta curve (Mhc/137) in D. (F) A model for the function of fruit fly Activin signaling in lifespan regulation through adult muscle tissues. In fruit fly muscle tissues, Activin signaling works as an anti-ageing factor, which up-regulates the major protein subunits of proteasomes so that any damaged or misfolded proteins can be cleared fast enough to ensure healthy status of the tissue. As a result of this regulation, fruit flies can achieve a longer healthy lifespan.