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Masayuki Amagai

Publications and source records attributed to Masayuki Amagai.

At least 19 recordsLinked to original sources
PubMed2026

Postzygotic biallelic inactivation of FDFT1 underlies solitary lesion formation in porokeratosis of Mibelli.

BACKGROUND: Porokeratosis reflects clonal expansion of keratinocytes with biallelic inactivation of mevalonate-cholesterol biosynthesis pathway genes. In disseminated porokeratosis (DP), lesions arise through independent somatic second hits in carriers of heterozygous germline pathogenic variants, whereas porokeratosis of Mibelli (PM) is usually solitary, and its molecular basis remains incompletely defined. OBJECTIVE: To elucidate the molecular basis of solitary PM. METHODS: We analyzed blood and lesional epidermis from seven patients with solitary PM within a 156-patient porokeratosis cohort using deep sequencing, copy-number/SNP profiling, and methylation analysis. RESULTS: Solitary PM plaques were larger and more irregular than the annular DP lesions. No pathogenic germline variants were detected in MVK, PMVK, MVD, FDPS, or FDFT1. Three patients had somatic biallelic genetic inactivation of FDFT1 through putative deleterious variants and/or focal microdeletions. The remaining four showed FDFT1 promoter hypermethylation with loss of heterozygosity (LOH) at the FDFT1 locus due to copy-neutral LOH or a monoallelic 8p deletion, consistent with early monoallelic epigenetic silencing, followed by genetic loss of the remaining active allele. In one patient, part of the plaque expanded centrifugally over 7.5 years. CONCLUSION: Solitary PM can be driven by postzygotic, lesion-restricted, biallelic inactivation of FDFT1 through genetic or epigenetic mechanisms within a single epidermal clone, promoting clonal expansion. This model may explain the tendency toward solitary PM lesions. The low probability of acquiring postzygotic biallelic inactivation without germline predisposition may underlie solitary PM and suggest a low recurrence risk for offspring, unlike DP driven by germline heterozygosity.

General dermatology↗
PubMed2006

T helper type 2-biased natural killer cell phenotype in patients with pemphigus vulgaris.

Pemphigus vulgaris (PV) is an autoantibody-mediated bullous disease, but the role of natural killer (NK) cells in its pathogenic process has never been examined in detail. Circulating CD56+ CD3- NK cells as well as CD69+-activated NK cells were increased in PV patients compared with healthy controls and patients with other autoantibody-mediated autoimmune diseases, including immune thrombocytopenic purpura and myasthenia gravis. Gene expression analysis of highly purified NK cells demonstrated an increased expression of IL-10 and decreased expression of IL-12Rbeta2, perforin, and granzyme B ex vivo in PV patients versus healthy controls. The NK cells from PV patients also showed impaired signal transducer and activator of transduction4 phosphorylation upon in vitro IL-12 stimulation. Moreover, NK cells from PV patients exhibited reduced IL-10 production in response to in vitro stimulation with IL-2/IL-12. Finally, IL-5 expression in NK cells was exclusively detected ex vivo in PV patients with active disease, and was lost in subsequent analyses performed during disease remission. Together these findings suggest that NK cells contribute to a T helper type 2-biased immune response in PV patients through impaired IL-12 signaling and an upregulation of IL-10 and IL-5.

Adult↗
PubMed2006

Synergistic pathogenic effects of combined mouse monoclonal anti-desmoglein 3 IgG antibodies on pemphigus vulgaris blister formation.

Pemphigus vulgaris (PV) is an autoimmune blistering disease caused by anti-desmoglein 3 (Dsg3) IgG antibodies. Previously, we generated an active mouse model for PV by adoptive transfer of splenocytes from immunized or naive Dsg3(-/-) mice. In this study, we isolated 10 anti-Dsg3 IgG mAbs (NAK-series) from PV model mice generated by transfer of naive Dsg3(-/-) splenocytes. We characterized their epitopes using domain-swapped and point-mutated Dsg1/Dsg3 molecules and examined their pathogenic activities in blister formation in three different assays. In a passive transfer model using neonatal mice, eight of 10 NAK mAbs showed pathogenic activity when injected together with half the minimum pathogenic dose of anti-Dsg1 IgG autoantibodies from pemphigus foliaceus (PF) patients. None of the mAbs could induce the PV phenotype when individual hybridoma clones were inoculated by peritoneal injection into adult Rag2(-/-) mice. NAK mAbs displayed a range of potency in an in vitro dissociation assay using primary cultured mouse keratinocytes. Interestingly, when multiple hybridoma clones recognizing different epitopes were inoculated in combination, recipient mice developed the PV phenotype. In vitro dissociation assays confirmed that combined NAK mAbs had synergistic pathogenic effects. These findings indicate that although an individual anti-Dsg3 IgG is not sufficient to cause blistering in adult mice, several together can induce the PV phenotype. These mAbs will provide a valuable tool to investigate the molecular mechanisms of blister formation, mimicking the effects of the polyclonal IgG antibodies found in patients.

Aging↗
PubMed2006

Tolerance induction by the blockade of CD40/CD154 interaction in pemphigus vulgaris mouse model.

Pemphigus vulgaris (PV) is an autoimmune blistering disease caused by IgG autoantibodies against desmoglein 3 (Dsg3). We have recently developed an active disease mouse model for PV by adoptive transfer of splenocytes from Dsg3(-/-) mice. The purpose of this study was to determine the role of CD40/CD154 interaction in the pathogenic antibody production and development of the disease in PV model mice. When anti-CD154 monoclonal antibody (mAb) was administered to recipient mice prior to adoptive transfer, anti-CD154 mAb almost completely blocked the anti-Dsg3 IgG production and prevented blister formation. The blockade of CD40/CD154 interaction induced tolerance against Dsg3 as the suppression of antibody production was observed through day 70, and it was maintained even after challenge by immunization with recombinant mouse Dsg3 or by adoptive transfer of immunized Dsg3(-/-) splenocytes. Furthermore, the tolerance to Dsg3 was transferable because cotransfer of splenocytes from anti-CD154 mAb-treated mice and naïve Dsg3(-/-) splenocytes significantly suppressed anti-Dsg3 IgG production in recipient mice. In contrast, when anti-CD154 mAb was injected after the mice had developed the PV phenotype, no significant suppression of the production of anti-Dsg3 IgG was observed. These findings indicate that the CD40/CD154 interaction is essential for the induction of pathogenic anti-Dsg3 IgG antibodies and that antigen-specific immune-regulatory cells induced by anti-CD154 mAb would hold a therapeutic option for autoimmune diseases.

Animals↗
PubMed2006

Non-pathogenic anti-desmoglein 3 IgG autoantibodies in Fogo Selvagem.

The endemic form of pemphigus foliaceus, fogo selvagem, is caused by IgG autoantibodies directed against desmoglein 1 (Dsg1). Hilario-Vargas and his colleagues describe a high prevalence of IgG autoantibodies against Dsg3, the target antigen of pemphigus vulgaris, in a Brazilian population where fogo selvagem is endemic, although those patients do not develop any apparent clinical phenotype of pemphigus vulgaris.

Autoantibodies↗
PubMed2006

Pathogenic monoclonal antibody against desmoglein 3 augments desmoglein 3 and p38 MAPK phosphorylation in human squamous carcinoma cell line.

Pemphigus vulgaris is an autoimmune blistering disease characterized by cell-cell detachment of epidermal cells. Autoantibody against desmoglein (Dsg) 3, a transmembrane glycoprotein that mediates the association of desmosomes, plays a major role in blistering in pemphigus vulgaris (PV). The mechanisms of autoantibody-induced acantholysis have not been clarified. We previously reported that PV-IgG induces phosphorylation of Dsg3, decreases Dsg3 on the cell surface and forms Dsg3-depleted desmosomes in cultured keratinocytes, and that cell treatment with a potent pathogenic monoclonal antibody against Dsg3 (AK23 mAb) decreases the amount of Dsg3 in cultured keratinocytes. Although the precise mechanisms remain unclear, we have proposed the involvement of intracellular signal transduction resulting from the binding of autoantibodies to Dsg3. In this study, we examined whether AK23 mAb augments phosphorylation of Dsg3 and p38 mitogen-activating protein kinase (MAPK) in a human squamous cell line, DJM-1 cells. AK23 mAb increased serine phosphorylation of Dsg3 and augmented activation levels of p38 MAPK. These results indicate that antibodies bind to Dsg3, but not other antigens, in the IgG fraction and can induce activation of signal transduction.

Adjuvants, Immunologic↗
PubMed2006

[Desmoglein, the target molecule in autoimmunity and infection].

To form the human body and maintain the integrity of its complex tissues, individual cells need to hold tightly to each other. The desmosome is the major type of intercellular adhesive junction, and has desmoglein (Dsg), a cadherin type cell-cell adhesion molecule, as a transmembrane component. Dsg is now known to be targeted in autoimmune diseases, infectious diseases, as well as inherited diseases. Patients with pemphigus, an autoimmune blistering disease of the skin and mucous membrane, have IgG autoantibodies directed against Dsg1 and Dsg3. A subset of patients with pemphigus have Dsg1/Dsg4 crossreacting IgG autoantibodies. Exfoliative toxins produced by Staphylococcal aureus, which causes Staphylococcal Scalded Skin Syndrome (SSSS) and bullous impetigo, specifically digest Dsg1. A subset of patients with SSSS develop a low titer of anti-Dsg1 IgG autoantibodies. A mutation in DSG1 gene causes striate palmoplantar keratoderma and a mutation in DSG4 gene causes inherited hypotrichosis. It is not clear why so many diseases are clustered in desmogleins, but there must be a reason for this. Studies on desmogleins will provide an important framework to understand the mysteries between autoimmunity and infection.

Animals↗
PubMed2005

Desmoglein endocytosis and desmosome disassembly are coordinated responses to pemphigus autoantibodies.

Desmosomes are adhesive intercellular junctions prominent in the skin and heart. Loss of desmosome function is associated with severe congenital and acquired disorders characterized by tissue fragility. Pemphigus vulgaris (PV) is an autoimmune disorder in which antibodies are directed against the desmosomal adhesion molecule Dsg3, resulting in severe mucosal erosions and epidermal blistering. To define the mechanisms by which Dsg3 autoantibodies disrupt keratinocyte adhesion, the fate of PV IgG and various desmosomal components was monitored in primary human keratinocytes exposed to PV patient IgG. PV IgG initially bound to keratinocyte cell surfaces and colocalized with desmosomal markers. Within 6 h after PV IgG binding to Dsg3, electron microscopy revealed that desmosomes were dramatically disrupted and keratinocyte adhesion was severely compromised. Immunofluorescence analysis indicated that PV IgG and Dsg3 were rapidly internalized from the cell surface in a complex with plakoglobin but not desmoplakin. Dsg3 internalization was associated with retraction of keratin filaments from cell-cell borders. Furthermore, the internalized PV IgG-Dsg3 complex colocalized with markers for both endosomes and lysosomes, suggesting that Dsg3 was targeted for degradation. Consistent with this possibility, biotinylation experiments demonstrated that soluble Dsg3 cell surface pools were rapidly depleted followed by loss of detergent-insoluble Dsg3. These findings demonstrate that Dsg3 endocytosis, keratin filament retraction, and the loss of keratinocyte cell-cell adhesion are coordinated responses to PV IgG.

Autoantibodies↗
PubMed2005

Enzyme-linked immunosorbent assay using bacterial recombinant proteins of human BP230 as a diagnostic tool for bullous pemphigoid.

BACKGROUND: By immunoblot analyses of normal human epidermal extracts, the 230kDa bullous pemphigoid antigen (BP230) is recognized by most bullous pemphigoid (BP) sera. We produced different recombinant glutathione-S-transferase-fusion proteins, which roughly presented N-terminal domain, central rod domain and C-terminal domain of human BP230. OBJECTIVE: In the present study, we developed an enzyme-linked immunosorbent assay (ELISA) using the recombinant proteins for detection of anti-BP230 IgG antibodies and assessed the usefulness of this assay in conjunction with an anti-BP180 ELISA to establish the diagnosis of BP. METHODS: Using the bacterial recombinant proteins of N-terminal and C-terminal domains, we developed an ELISA. A receiver-operating-characteristic (ROC) analysis was performed to determine a cut-off value for the BP230 ELISA. RESULTS: By this BP230 ELISA, 173 (72.4%) of 239 BP sera were positive, while only one (1.1%) of 94 sera from pemphigus vulgaris and pemphigus foliaceus patients was positive and all the 109 normal control sera were negative. Thus, the sensitivity and specificity of the BP230 ELISA were 72.4 and 99.5%, respectively. Interestingly, while 54 (84.4%) of 64 BP sera in active stage and 113 (64.6%) of 175 BP sera in remission were positive in BP180 ELISA, 37 (57.8%) of 64 BP sera in active stage and 136 (77.7%) of 175 BP sera in remission were positive in BP230 ELISA. These results indicate that the titer of anti-BP230 antibodies is not related with disease activity in some BP cases. Most significantly, by combining the results of BP230 ELISA and BP180 ELISA, 232 (97.1%) of 239 BP sera were positive. CONCLUSION: The combination of BP230 ELISA and BP180 ELISA is the highly sensitive method for the diagnosis of BP.

Autoantigens↗
PubMed2005

Staphylococcus hyicus exfoliative toxins selectively digest porcine desmoglein 1.

Virulent strains of Staphylococcus hyicus can cause exudative epidermitis in pigs. The major symptom of this disease is exfoliation of the skin in the upper stratum spinosum. Exfoliation of the skin is strongly associated with exfoliative toxin including ExhA, ExhB, ExhC, ExhD, SHETA, and SHETB. Recently, genes for ExhA, ExhB, ExhC and ExhD were cloned. Exfoliative toxins produced by S. aureus have been shown to selectively cleave human or mouse desmoglein 1, a desmosomal adhesion molecule, that when inactivated results in blisters. In this study, we attempted to identify the molecular target of Exhs in porcine skin. Each of recombinant Exhs injected in the skin of pigs caused superficial epidermal blisters or crust formation. Cell surface staining of desmoglein 1, but not that of desmoglein 3, was abolished when cryosections of normal porcine skin were incubated with one of Exhs suggesting that Exh selectively degrade porcine desmoglein 1. In vitro incubation of the recombinant extracellular domains of desmoglein 1 and desmoglein 3 of human, mouse or canine origin demonstrated that only mouse desmogleins 1alpha and 1beta were cleaved by ExhA and ExhC at high concentration. Furthermore, injection of ExhA and ExhC at high concentration caused superficial blisters in neonatal mice. These findings strongly suggest that Exhs cause blister formation of porcine skin by digesting porcine desmoglein 1 in a similar fashion to exfoliative toxins from S. aureus.

Animals↗
PubMed2005

Cutaneous type pemphigus vulgaris: a rare clinical phenotype of pemphigus.

Pemphigus is an autoimmune blistering disease of the skin, mucous membranes, or both. There are two main categories of pemphigus: pemphigus foliaceus (PF) and pemphigus vulgaris (PV). PV is further subdivided into mucosal dominant and mucocutaneous types, according to the extent of cutaneous lesions. These classes of pemphigus have distinct histopathologic and serologic findings, with most cases falling into these subtypes. We report 4 cases that clinically showed blisters and erosions in the skin only, without mucosal involvement. Histologic examination of cutaneous lesions demonstrated suprabasilar acantholysis, a typical finding for PV. These patients had predominant anti-desmoglein 1 (Dsg1) IgG autoantibodies as well as anti-Dsg3 IgG autoantibodies, as determined by enzyme-linked immunosorbent assay. The desmoglein compensation theory posits that this rare phenotype can be produced by pathogenically weak anti-Dsg3 IgG in the presence of potent anti-Dsg1 IgG autoantibodies. Thus, cutaneous type PV without apparent mucosal involvement is observed as a rare clinical and histologic expression of pemphigus. This expression can be a transient phenotype that may develop from, or evolve into, other subtypes of pemphigus.

Autoantibodies↗