The dissertation is devoted to the complex physiological and biochemical study of the role of signaling pathways in the intestinal stem cells (ISCs) and their undifferentiated progenitor cells enteroblasts (EB), which causes some physiological and metabolic consequences. These manipulations affected the stress resistance, feeding and fecundity rate, metabolic processes, and lifespan of Drosophila.
Bipartite Gal4-UAS system was used to generate the experimental fly lines with the inhibition or activation of signaling pathways TOR, IS, and overexpression of Myc transcription factor in ISCs and EB. We found, that both, inhibition and activation of TOR and IS signaling pathways, as well as Myc coexpression in ISCs, decreased Drosophila lifespan. Experimental females were more sensitive to oxidative stress and starvation. We found, low-calorie diet extended the lifespan in flies with activated TOR signaling in ISCs. Moreover, malnutrition increased the survival of females with inr knockdown in ISCs.
A decreased of feeding and fecundity rate was observed in females with IS inhibition in ISCs, and the tendency of increase of these parameters was detected in females with IS activation. On the contrary to IS, the TOR pathway activation did not affect fertility, but reduced appetite, while inhibition did not affect appetite, but led to increased fertility. It was also demonstrated, that Myc coexpression reduced these physiological parameters. We found lower glucose concentrations in fly body and hemolymph when signaling pathways were inhibited, and significantly higher when activated. Interestingly, the inhibition of TOR and IS in ISCs and EB reduced the contents of stored glycogen and triglycerides (TAG), but TOR and IS inhibition in the EB significantly increased these traits. We also showed an important role of genes of DILP-AKH system in the modulation of metabolic processes in response to the TOR/IS/Myc inhibition/activation in ISCs and EB.
Measurements of gut integrity with the” Smurf” assay showed that perturbation of TOR/IS/Myc did not affect tissue integrity. However, our experimental study established, that TOR/IS/Myc functions in close coordination with JAK/STAT, EGFR, JNK, and insulin signaling for the control of homeostasis of ISCs. This interaction occurs at the level of signaling ligands. For the first time, the mechanisms have been established in which the signaling system TOR/IS/Myc acts in a small population of stem cells and affect metabolism and physiological processes. Besides, physiological effects from inhibition/activation of signaling pathways on the state of the organism Drosophila were first detected. Therefore, the obtained data reveal new interesting prospects in the studies of physiology and metabolic processes of the fruit fly.
