A case of periodic-fever-syndrome-like disorder with lipodystrophy, myositis, and autoimmune abnormalities

Proteostasis Perturbations and Their Roles in Causing Sterile Inflammation and Autoinflammatory Diseases

Proteostasis, a portmanteau of the words protein and homeostasis, refers to the ability of eukaryotic cells to maintain a stable proteome by acting on protein synthesis, quality control and/or degradation. Over the last two decades, an increasing number of disorders caused by proteostasis perturbations have been identified. Depending on their molecular etiology, such diseases may be classified into ribosomopathies, proteinopathies and proteasomopathies. Strikingly, most—if not all—of these syndromes exhibit an autoinflammatory component, implying a direct cause-and-effect relationship between proteostasis disruption and the initiation of innate immune responses. In this review, we provide a comprehensive overview of the molecular pathogenesis of these disorders and summarize current knowledge of the various mechanisms by which impaired proteostasis promotes autoinflammation. We particularly focus our discussion on the notion of how cells sense and integrate proteostasis perturbations as danger signals in the context of autoinflammatory diseases to provide insights into the complex and multiple facets of sterile inflammation.

Myositis with sarcoplasmic inclusions in Nakajo-Nishimura syndrome: a genetic inflammatory myopathy

AIMS

Nakajo-Nishimura syndrome (NNS) is an autosomal recessive disease caused by biallelic mutations in the PSMB8 gene that encodes the immunoproteasome subunit β5i. There have been only a limited number of reports on the clinicopathological features of the disease in genetically confirmed cases.

METHODS

We studied clinical and pathological features of three NNS patients who all carry the homozygous p.G201V mutations in PSMB8. Patients' muscle specimens were analysed with histology and immunohistochemistry.

RESULTS

All patients had episodes of typical periodic fever and skin rash, and later developed progressive muscle weakness and atrophy, similar to previous reports. Oral corticosteroid was used for treatment but showed no obvious efficacy. On muscle pathology, lymphocytes were present in the endomysium surrounding non-necrotic fibres, as well as in the perimysium perivascular area. Nearly all fibres strongly expressed MHC-I in the sarcolemma. In the eldest patient, there were abnormal protein aggregates in the sarcoplasm, immunoreactive to p62, TDP-43 and ubiquitin antibodies.

CONCLUSIONS

These results suggest that inflammation, inclusion pathology and aggregation of abnormal proteins underlie the progressive clinical course of the NNS pathomechanism.

Dysregulation of immunoproteasomes in autoinflammatory syndromes

Immunoproteasomes degrade ubiquitin-coupled proteins and play a role in creating peptides for presentation by MHC class I proteins. Studies of gene-deficient mice, in which each immunoproteasomal subunit was affected, have demonstrated that dysfunction of immunoproteasomes leads to immunodeficiency, i.e. reduced expression of MHC class I and attenuation of CD8 T-cell responses. Recent studies, however, have uncovered a new type of autoinflammatory syndrome characterized by fever, nodular erythema and progressive partial lipodystrophy that is caused by genetic mutations in immunoproteasome subunits. These mutations disturbed the assembly of immunoproteasomes, which led to reduced proteasomal activity and thus accumulation of ubiquitin-coupled proteins. Those findings suggest that immunoproteasomes function as anti-inflammatory machinery in humans. The discovery of a new type of autoinflammatory syndrome caused by dysregulated immunoproteasomes provides novel insights into the important roles of immunoproteasomes in inflammation as well as the spectrum of autoinflammatory diseases.

Dysfunctional immunoproteasomes in autoinflammatory diseases

Recent progress in DNA sequencing technology has made it possible to identify specific genetic mutations in familial disorders. For example, autoinflammatory syndromes are caused by mutations in gene coding for immunoproteasomes. These diseases include Japanese autoinflammatory syndrome with lipodystrophy, Nakajo-Nishimura syndrome, joint contractures, muscular atrophy, microcytic anemia, panniculitis-associated lipodystrophy syndrome, and chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature syndrome. Causal mutations of these syndromes are present in gene coding for subunits of the immunoproteasome. Importantly, a genetically modified mouse that lacks the catalytic subunit of immunoproteasomes does not always develop an autoinflammatory syndrome. Analysis of causal gene mutations, assessment of patients’ phenotypic changes, and appropriate animal models will be indispensable for clarifying the underlying mechanisms responsible for the development of autoinflammatory syndromes and establishing curative approaches.

Proteasome-associated autoinflammatory syndromes: advances in pathogeneses, clinical presentations, diagnosis, and management

The disease spectrum currently known as the proteasome-associated autoinflammatory syndromes (PRAAS) was first described in 1939 in patients who presented with recurrent fevers beginning in infancy or early childhood, which were accompanied by nodular erythema, a pernio-like rash, and joint contractures. Since then, several syndromes, such as chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature (CANDLE) syndrome, Nakajo-Nishimura syndrome (NNS), joint contractures, muscle atrophy, microcytic anemia and panniculitis-induced lipodystrophy (JMP) syndrome, and Japanese autoinflammatory syndrome with lipodystrophy (JASL), have been used to categorize patients with diseases within the same spectrum. Recently, independent studies have identified mutations in the human proteasome subunit β type 8 (PSMB8) gene, which result in a sustained inflammatory response in all syndromes. Further functional studies not only suggest a causative role of PSMB8 mutations but also imply that they represent one disease spectrum, referred to as PRAAS. In this paper, we review the clinical presentations and laboratory findings of PRAAS, as well as the most recent advances in pathogeneses, diagnosis, and treatment options for patients with diseases in this spectrum.

Nakajo-Nishimura syndrome: an autoinflammatory disorder showing pernio-like rashes and progressive partial lipodystrophy

Nakajo-Nishimura syndrome (ORPHA2615; also registered as Nakajo syndrome in OMIM#256040) is a distinct inherited inflammatory and wasting disease, originally reported from Japan. This disease usually begins in early infancy with a pernio-like rash, especially in winter. The patients develop periodic high fever and nodular erythema-like eruptions, and gradually progress lipomuscular atrophy in the upper body, mainly the face and the upper extremities, to show the characteristic thin facial appearance and long clubbed fingers with joint contractures. So far about 30 cases have been reported from Kansai, especially Wakayama and Osaka, Tohoku and Kanto areas. At present, about 10 cases are confirmed to be alive only in the Kansai area, including one infant case in Wakayama. However, more cases are expected to be added in the near future. Although cause of the disease has long been undefined, a homozygous mutation of the PSMB8 gene, which encodes the β5i subunit of immunoproteasome, has been identified to be responsible in 2011. By analyses of the patients-derived cells and tissues, it has been suggested that accumulation of ubiquitinated and oxidated proteins due to immunoproteasome dysfunction causes hyperactivation of p38 mitogen-activated protein kinase and interleukin-6 overproduction. Since similar diseases with PSMB8 mutations have recently been reported from Europe and the United States, it is becoming clear that Nakajo-Nishimura syndrome and related disorders form proteasome disability syndromes, a new category of autoinflammatory diseases distributed globally.

Immunology in clinic review series; focus on autoinflammatory diseases: update on monogenic autoinflammatory diseases: the role of interleukin (IL)-1 and an emerging role for cytokines beyond IL-1

OTHER THEMES PUBLISHED IN THIS IMMUNOLOGY IN THE CLINIC REVIEW SERIES Allergy, Host Responses, Cancer, Type 1 diabetes and viruses, Metabolic diseases.

SUMMARY

The disease-based discovery of the molecular basis for autoinflammatory diseases has led not only to a rapidly growing number of clinically and genetically identifiable disorders, but has unmantled key inflammatory pathways such as the potent role of the alarm cytokine interleukin (IL)-1 in human disease. Following its initial failures in the treatment of sepsis and the moderate success in the treatment of rheumatoid arthritis, IL-1 blocking therapies had a renaissance in the treatment of a number of autoinflammatory conditions, and IL-1 blocking therapies have been Food and Drug Administration (FDA)-approved for the treatment of the autoinflammatory conditions: cryopyrin-associated periodic syndromes (CAPS). CAPS and deficiency of the IL-1 receptor antagonist (DIRA), both genetic conditions with molecular defects in the IL-1 pathway, have provided a pathogenic rationale to IL-1 blocking therapies, and the impressive clinical results confirmed the pivotal role of IL-1 in human disease. Furthermore, IL-1 blocking strategies have shown clinical benefit in a number of other genetically defined autoinflammatory conditions, and diseases with clinical similarities to the monogenic disorders and not yet identified genetic causes. The discovery that IL-1 is not only triggered by infectious danger signals but also by danger signals released from metabolically 'stressed' or even dying cells has extended the concept of autoinflammation to disorders such as gout, and those that were previously not considered inflammatory, such as type 2 diabetes, coronary artery disease, obesity and some degenerative diseases, and provided the conceptual framework to target IL-1 in these diseases. Despite the tremendous success of IL-1 blocking therapy, the use of these agents in a wider spectrum of autoinflammatory conditions has uncovered disease subsets that are not responsive to IL-1 blockade, including the recently discovered proteasome-associated autoinflammatory syndromes such as chronic atypical neutrophilic dermatitis with lipodystrophy and elevated temperatures (CANDLE), Japanese autoinflammatory syndrome with lipodystrophy (JASL), Nakajo-Nishimura syndrome (NNS) and joint contractures, muscle atrophy, panniculitis induced lipodystrophy (JMP), and urge the continued quest to characterize additional dysregulated innate immune pathways that cause autoinflammatory conditions.

Proteasome assembly defect due to a proteasome subunit beta type 8 (PSMB8) mutation causes the autoinflammatory disorder, Nakajo-Nishimura syndrome

Nakajo-Nishimura syndrome (NNS) is a disorder that segregates in an autosomal recessive fashion. Symptoms include periodic fever, skin rash, partial lipomuscular atrophy, and joint contracture. Here, we report a mutation in the human proteasome subunit beta type 8 gene (PSMB8) that encodes the immunoproteasome subunit β5i in patients with NNS. This G201V mutation disrupts the β-sheet structure, protrudes from the loop that interfaces with the β4 subunit, and is in close proximity to the catalytic threonine residue. The β5i mutant is not efficiently incorporated during immunoproteasome biogenesis, resulting in reduced proteasome activity and accumulation of ubiquitinated and oxidized proteins within cells expressing immunoproteasomes. As a result, the level of interleukin (IL)-6 and IFN-γ inducible protein (IP)-10 in patient sera is markedly increased. Nuclear phosphorylated p38 and the secretion of IL-6 are increased in patient cells both in vitro and in vivo, which may account for the inflammatory response and periodic fever observed in these patients. These results show that a mutation within a proteasome subunit is the direct cause of a human disease and suggest that decreased proteasome activity can cause inflammation.