Ryzhakov, G. | bioRxiv Science

bioRxiv2024

Structural basis of dual BACH1 regulation by SCFFBXO22 and SCFFBXL17

BTB and CNC homolog 1 (BACH1) is a master transcriptional regulator of the cellular oxidative stress response and pro-metastatic oncogene. Post-translational stability of BACH1 is tightly regulated by distinct F-box ubiquitin ligases, including SCFFBXO22 and SCFFBXL17. However, the molecular details have been elusive. Here, we reveal a structural switch in FBXO22 that controls the recognition of a three-dimensional degron in the BACH1 BTB domain, thus explaining its specificity for dimeric BACH1. We describe how cancer-associated mutations in FBXO22 modulate binding and ubiquitylation of BACH1. Further, we reveal that cancer-related mutations or cysteine-modifications destabilize the BTB domain and redirect BACH1 to FBXL17, where it is recognized as a monomer. This explains how complementary ligases post-translationally regulate BACH1 depending on the state of its BTB domain. Our findings provide mechanistic insights into the regulation of the oxidative stress response and may spur therapeutic strategies to targeting oxidative stress-related disorders and metastatic cancers.

biophysics↗

bioRxiv2020

PYK2 controls intestinal inflammation via activation of IRF5 in macrophages

Inflammatory bowel disease (IBD) is a group of inflammatory disorders of the gastro-intestinal tract caused by a complex combination of genetic and environmental factors. Interferon regulating factor 5 (IRF5) is a multifunctional regulator of immune responses, which plays a key pathogenic role in mouse colitis models and is a genetic risk factor for IBD. A screen of a protein kinase inhibitor library in macrophages revealed a list of putative IRF5 kinases. Among the top hits validated in multiple in vitro assays, protein-tyrosine kinase 2-beta (PTK2B or PYK2) was identified as the only IBD genetic risk factor, known to impact gene expression in myeloid cells1,2. Phospho-proteomics and mutagenesis analyses established that PYK2 directly phosphorylates and activates IRF5 at tyrosine (Y) 171. IRF5 nuclear translocation and recruitment to target genes was impaired in PYK2-deficient cells or in cells treated with PYK2 inhibitors. Importantly, macrophage transcriptomic signature under PYK2 inhibition phenocopied IRF5 deficiency. Treatment with a PYK2 inhibitor reduced pathology and inflammatory cytokine production in Helicobacter hepaticus + anti-IL-10R antibody induced colitis model. It also decreased levels of pro-inflammatory cytokines in human colon biopsies taken from patients with ulcerative colitis. Thus, we have identified a major role for PYK2 in regulating the inflammatory response and mapped its activity to the IRF5 innate sensing pathway, opening opportunities for therapeutic interference with it in IBD and other inflammatory conditions.

immunology↗