Ebstein, F. | Search bioRxiv

bioRxiv2020

Immunoproteasome impairment via β5i/LMP7-deletion leads to sustained pancreatic injury and delayed recovery from experimental pancreatitis.

Background & AimsUncovering potential new targets involved in pancreas recovery may permit the development of new therapies and improvement of pancreatitis treatment. One disease mechanism comprises the endoplasmic reticulum stress response and a key regulator to prevent proteotoxic stress in an inflammatory context is the immunoproteasome, an induced form of the constitutive proteasome. Our aim was therefore to investigate the role of the immunoproteasome in acute pancreatitis. MethodsAcute pancreatitis was induced in wild type and LMP7-/- mice and several biochemical parameters for disease severity were addressed, including protease activities and histology of pancreatic damage. Real-time PCR was used to measure pro-inflammation and unfolded protein response. Serum IL-6 was detected by cytometric bead assay. Western blotting was used to quantify the ratio of ubiquitin-protein conjugates as well as unfolded protein response activation. Immunofluorescence identified leukocytes infiltration as well as ubiquitin-protein conjugates in the pancreas. ResultsIn this study, we demonstrate that the {beta}5i/LMP7-subunit deletion correlates with persistent pancreatic damage. Interestingly, immunoproteasome-deficient mice unveil increased activity of pancreatic enzymes as well as higher secretion of Interleukin-6 and transcript expression of the Interleukin IL-1{beta}, IFN-{beta} cytokines and the CXCL-10 chemokine. Thereafter, acinar cell death was increased, which appears to be due to the greater accumulation of ubiquitin-protein conjugates and prolonged unfolded protein response. ConclusionsOur findings suggest that the immunoproteasome plays a protective role in acute pancreatitis via its role in the clearance of damaged proteins and the balance of ER-stress responses in pancreatic acini as well as in macrophages cytokine production.

physiology↗

bioRxiv2019

Proteasome subunit PSMC3 variants cause neurosensory syndrome combining deafness and cataract due to proteotoxic stress

Whole-genome sequencing was performed on patients with severe deafness and early-onset cataracts as part of a neurological, sensorial and cutaneous novel syndrome. A unique deep intronic homozygous variant in the PSMC3 gene (c.1127+337A>G, p.Ser376Argfs15*), encoding the 26S proteasome ATPase ring subunit 5 (Rpt5) was identified leading to the transcription of a cryptic exon. Patients fibroblasts exhibited impaired protein homeostasis characterized by accumulation of ubiquitinated proteins suggesting severe proteotoxic stress. Indeed, the TCF11/Nrf1 transcriptional pathway allowing proteasome recovery after proteasome inhibition is permanently activated in the patients fibroblasts. Upon chemical proteasome inhibition this pathway is however impaired. These cells were unable to compensate for proteotoxic stress although a higher proteasome content. Two different zebrafish studies led to inner ear development anomalies as well as cataracts. PSMC3 proteasome subunit dysfunction leads to various neurological manifestations, early onset cataracts and deafness and suggest that Rpt5 plays a major role in inner ear, lens and central nervous system development.

genetics↗