ABSTRACT
Impaired proteasome activity due to genetic variants of certain subunits might lead to proteasome-associated autoinflammatory syndromes (PRAAS). Here we report a de novo heterozygous missense variant of the PSMB9 proteasome subunit gene in two unrelated Japanese infants resulting in amino acid substitution of the glycine (G) by aspartic acid (D) at position 156 of the encoded protein ß1i. In addition to PRAAS-like manifestations, these individuals suffer from pulmonary hypertension and immunodeficiency, which are distinct from typical PRAAS symptoms. The missense variant results in impaired immunoproteasome maturation and activity, yet ubiquitin accumulation is hardly detectable in the patients. A mouse model of the heterozygous human genetic variant (Psmb9G156D/+) recapitulates the proteasome defects and the immunodeficiency phenotype of patients. Structurally, PSMB9 G156D interferes with the ß-ring-ßring interaction of the wild type protein that is necessary for 20S proteasome formation. We propose the term, proteasome-associated autoinflammatory syndrome with immunodeficiency (PRAAS-ID), to indicate a separate category of autoinflammatory diseases, similar to, but distinct from PRAAS, that describes the patients in this study.
Subject(s)
Cysteine Endopeptidases/genetics , Hereditary Autoinflammatory Diseases/genetics , Hypertension, Pulmonary/genetics , Primary Immunodeficiency Diseases/genetics , Proteasome Endopeptidase Complex/metabolism , Animals , Cysteine Endopeptidases/metabolism , Disease Models, Animal , Female , Hereditary Autoinflammatory Diseases/diagnosis , Hereditary Autoinflammatory Diseases/immunology , Hereditary Autoinflammatory Diseases/pathology , Heterozygote , Humans , Hypertension, Pulmonary/diagnosis , Hypertension, Pulmonary/immunology , Infant, Newborn , Male , Mice , Mice, Transgenic , Mutation, Missense , Pedigree , Primary Immunodeficiency Diseases/diagnosis , Primary Immunodeficiency Diseases/immunology , Primary Immunodeficiency Diseases/pathology , Proteasome Endopeptidase Complex/genetics , SyndromeABSTRACT
Cholera toxin B (CTB) is a subunit of cholera toxin, a bacterial enterotoxin secreted by Vibrio cholerae and also functions as an immune adjuvant. However, it remains unclear how CTB activates immune cells. We here evaluated whether or how CTB induces production of a pro-inflammatory cytokine, interleukin-1ß (IL-1ß). CTB induced IL-1ß production not only from bone marrow-derived macrophages (BMMs) but also from resident peritoneal macrophages in synergy with O111:B4-derived lipopolysaccharide (LPS O111:B4) that can bind to CTB. Meanwhile, when prestimulated with O55:B5-derived LPS (LPS O55:B5) that fails to bind to CTB, resident peritoneal macrophages, but not BMMs, produced IL-1ß in response to CTB. The CTB-induced IL-1ß production in synergy with LPS in both peritoneal macrophages and BMMs was dependent on ganglioside GM1, which is required for internalization of CTB. Notably, not only the NLRP3 inflammasome but also the pyrin inflammasome were involved in CTB-induced IL-1ß production from resident peritoneal macrophages, while only the NLRP3 inflammasome was involved in that from BMMs. In response to CTB, a Rho family small GTPase, RhoA, which activates pyrin inflammasome upon various kinds of biochemical modification, increased its phosphorylation at serine-188 in a GM1-dependent manner. This phosphorylation as well as CTB-induced IL-1ß productions were dependent on protein kinase A (PKA), indicating critical involvement of PKA-dependent RhoA phosphorylation in CTB-induced IL-1ß production. Taken together, these results suggest that CTB, incorporated through GM1, can activate resident peritoneal macrophages to produce IL-1ß in synergy with LPS through novel mechanisms in which pyrin as well as NLRP3 inflammasomes are involved.
