Protein folding homeostasis - from mechanisms to interventions

The unfolded protein response by which cells adapt their endoplasmic reticulum (ER) to changing levels of ER-stress, globally promotes fitness in eukaryotes. However, the outcome of specific pathological processes associated with ER stress may be improved by modulating the activity of specific strands of the UPR. Here we shall focus on three promising yet understudied aspects of the response, in hope of uncovering details that will enable us to exploit failures of homeostasis in the UPR. All three involve enzymes that we hope to attack with modern tools of Cryo-EM, CRISPR-based gene editing, somatic cell genetics, small-molecule (metabol)omics and structure-based tool-compound discovery. The key ER chaperone BiP is regulated post-translationally by FICD-mediated AMPylation/deAMPylation. Understanding this bi-functional enzyme will provide a handle to manipulate conditions in the ER. Stress-mediated attenuation of protein synthesis hinges on phosphorylated eIF2 attenuating the nucleotide exchange factor eIF2B via a recently discovered allosteric mechanism. We will search for endogenous metabolites and chemical ligands that exploit this path to allosterically regulate eIF2B bi-directionally. The eIF2-directed holophosphatase that terminates signalling, has recently become accessible to structural studies; these we aim to deepen in hope of devising strategies to target this recalcitrant strand of the stress response pathway.