The anticancer methylthioadenosine phosphorylase transition-state inhibitor induces autophagy in humanized yeast Open Access

Methylthioadenosine-DADMe immucillin-A (MTDIA) is a transition-state analog that potently inhibits 5’-methylthioadenosine phosphorylase (MTAP) at picomolar concentrations and elicits anti-tumour activity against lung, prostate, colon, cervical, head and neck, and triple-negative breast cancers in cell and animal models. The anticancer mechanisms of MTDIA involve elevated methylthioadenosine but are not fully understood. MEU1 is expressed in yeast and is functionally equivalent to the human MTAP. To gain further understanding we performed chemical genetic analyses via gene deletion and GFP-tagged protein libraries in yeast expressing the human equilibrative nucleoside transporter to permit MTDIA uptake. Genomic and proteomic analyses identified genes and proteins critical to MTDIA bioactivity. Network analysis of these genes and proteins revealed an important link to ribosomal function, which was confirmed with reduced abundance of ribosomal subunit proteins. Network analysis also implicated autophagy, which was confirmed with intracellular trafficking of GFP-Atg8 and phloxine B viability. A comparable effect occurred by deletion of yeast MEU1, indicating a single target for MTDIA in yeast. Overall, our yeast model reveals specific components of the ribosome and autophagy induction as integral mechanisms mediating the bioactivity of MTDIA.