JAK/STAT1 signaling promotes HMGB1 hyperacetylation and nuclear translocation

Abstract

Extracellular high-mobility group box (HMGB)1 mediates inflammation during sterile and infectious injury and contributes importantly to disease pathogenesis. The first critical step in the release of HMGB1 from activated immune cells is mobilization from the nucleus to the cytoplasm, a process dependent upon hyperacetylation within two HMGB1 nuclear localization sequence (NLS) sites. The inflammasomes mediate the release of cytoplasmic HMGB1 in activated immune cells, but the mechanism of HMGB1 translocation from nucleus to cytoplasm was previously unknown. Here, we show that pharmacological inhibition of JAK/STAT1 inhibits LPS-induced HMGB1 nuclear translocation. Conversely, activation of JAK/STAT1 by type 1 interferon (IFN) stimulation induces HMGB1 translocation from nucleus to cytoplasm. Mass spectrometric analysis unequivocally revealed that pharmacological inhibition of the JAK/STAT1 pathway or genetic deletion of STAT1 abrogated LPS-or type 1 IFN-induced HMGB1 acetylation within the NLS sites. Together, these results identify a critical role of the JAK/STAT1 pathway in mediating HMGB1 cytoplasmic accumulation for subsequent release, suggesting that the JAK/STAT1 pathway is a potential drug target for inhibiting HMGB1 release.damage-associated molecular pattern | cytokine | pathogen-associated molecular pattern | innate immunity | therapy H igh-mobility group box 1 (HMGB1), a ubiquitous DNAbinding protein, is a promiscuous sensor driving nucleic acidmediated immune responses and a pathogenic inflammatory mediator in sepsis, arthritis, colitis, and other disease syndromes (1-5). Immune cells actively release HMGB1 after activation by exposure to pathogen-associated molecular patterns or damageassociated molecular patterns, including lipopolysaccharide (LPS) and inflammasome agonists (1, 6, 7). High levels of extracellular HMGB1 accumulate in patients with infectious and sterile inflammatory diseases. Extracellular disulfide HMGB1 stimulates macrophages to release TNF and other inflammatory mediators by binding and signaling through Toll-like receptor (TLR)4. Reduced HMGB1 facilitates immune cell migration by interacting with the receptor for advanced glycation end products (RAGE) and CXCL12 (8-12), a process regulated by posttranslational redox-dependent mechanisms. Administration of neutralizing anti-HMGB1 mAbs or other HMGB1 antagonists significantly reduces the severity of inflammatory disease, promotes bacterial clearance during Pseudomonas aeruginosa or Salmonella typhimurium infection and attenuates memory impairment in sepsis survivors (1,(13)(14)(15). Together, these and other findings indicate the importance of a mechanistic understanding of HMGB1 release from activated immune cells and the regulatory signaling pathways controlling these processes.Most cytokines harbor a leader peptide that facilitates secretion through the endoplasmic reticulum-Golgi exocytotic route. HMGB1, which lacks a leader peptide, is released via unconventional protein secretion pathways (1, 6, 7). In quiescent cells, most ...

High Mobility Group Box Protein 1 (HMGB1): The Prototypical Endogenous Danger Molecule

“…Passive release, which occurs in the context of necrotic cell death, is nearly instantaneous. Active HMGB1 secretion is a much slower process that requires two essential steps: the initial step is to translocate nuclear HMGB1 to the cytoplasm, which depends on JAK-STAT signaling that will generate hyperacetylation of critical lysine residues located in the two NLS sites (26). This molecular modification of HMGB1 prevents the continuous bidirectional shuttle of HMGB1 between the cytoplasm and the nucleus and leads to cytoplasmic accumulation of hyperacetylated HMGB1.…”

Serum Amyloid A Stimulates PKR Expression and HMGB1 Release Possibly through TLR4/RAGE Receptors

“…Emerging evidence has revealed an important role for PKR (30) and STAT1 (28) in LPS-induced HMGB1 release. To evaluate this mechanism of SAA-mediated HMGB1 release, we examined the effects of TLR4/RAGE deficiency on SAAinduced activation of these signaling molecules.…”

“…The nucleus-to-cytoplasm translocation of HMGB1 is mediated by the STAT1-mediated acetylation of the HMGB1 nuclear-localization sequences (28). The extracellular HMGB1 release is regulated by caspase 1-and the doublestranded RNA-activated protein kinase R (PKR)-dependent inflammasome activation (29,30), pyroptosis (31) or necroptosis (32).…”

Leukocytes recruited by tumor-derived HMGB1 sustain peritoneal carcinomatosis

“…HMGB1 is passively released by dying cells and actively generated in inflammatory conditions: it acts in the extracellular environment as a prototypical DAMP/alarmin. [10][11][12][13] Little is known on the role of HMGB1 in peritoneal carcinogenesis. We have recently observed that HMGB1 released as a consequence of 5-fluorouracil based chemotherapy activates autophagic and apoptotic pathways and might contribute to the resistance of cancer cells to conventional chemotherapy.…”