Dictyostelium discoideum Sir2D modulates cell-type specific gene expression and is involved in autophagy

Abstract

Sirtuins (SIRTs) belong to class III histone deacetylases and require NAD for their activity. Their activity is associated with the nutritional status of the cell and they directly link cellular metabolic signalling to the state of protein post-translational modifications. Sirtuins play an important role in healthy aging, longevity and age-related diseases, as well as in cell survival mechanisms, such as autophagy. Here, we investigate the functions of Dictyostelium discoideum Sir2D which shows similarity to human SIRT1. This gene is expressed throughout growth and development. Overexpression of sir2D promotes cell proliferation and the corresponding fusion protein shows nuclear localization. To facilitate the study of the function of Sir2D, we created a sir2D knockout by gene disruption. This mutant exhibits inhibited cell proliferation and developmental defects, including smaller aggregates and multi-tipped structures. When developed as chimeras with wild-type cells, the sir2D cells show a reduced ability to form spores. Prespore and prestalk differentiation was also impaired in the mutant strain. Sir2D regulates the expression of several autophagic genes (Atgs) and the sir2D deficient strain shows reduced autophagic flux. In conclusion, Sir2D plays a role in cell differentiation, modulates the expression of both prespore and prestalk genes and participates in the process of autophagy.

A two-pore channel protein required for regulating mTORC1 activity on starvation

“…In other systems, RFP-GFP-Atg8 has been used to measure autophagic flux as the GFP signal is quenched on the fusion of the autophagosome with the lysosome. However, in agreement with other reports using this marker in Dictyostelium [36,37], very few red-only punctae were seen (Fig. 5d, Additional file 5: Figure S5).…”

“…However, in Dictyostelium cells (strain Ax4) expressing this marker, no RFP-only punctae have been seen unless the acidic vesicle pH is increased by incubation with weak bases, suggesting that in the absence of weak base, the pH may be low enough to quench even the RFP signal [36]. There is a single report suggesting a very low number of RFP-only punctae in Ax2 cells [37]. The low number we see here in Ax2 cells is consistent with these observations.…”

Legionella pneumophila Infection Rewires the Acanthamoeba castellanii Transcriptome, Highlighting a Class of Sirtuin Genes

“…We found that silencing of sir6f inhibited A. castellanii cell proliferation during infection but did not affect cell viability. This is consistent with Sir2D knockout strains of D. discoideum that show reduced cell proliferation (Lohia et al, 2017). However, sir6f silencing in A. castellanii did result in reduced L. pneumophila replication, suggesting that the upregulation of sir6f during L. pneumophila infection is advantageous to the pathogen, although the mechanism is unknown.…”

Autophagy and inflammation

“…Conversely, chemical inhibitors of autophagy will promote infection [80]. Additional studies have implicated the role of autophagy in defense against other microbial pathogens, such as Legionella pneumophila [81], Dictyostelium discoideum [82], Shigella [83] and so on.…”