Mami Yamamoto

Neutral Cysteine Protease Bleomycin Hydrolase Is Essential for the Breakdown of Deiminated Filaggrin into Amino Acids

Filaggrin is a component of the cornified cell envelope and the precursor of free amino acids acting as a natural moisturizing factor in the stratum corneum. Deimination is critical for the degradation of filaggrin into free amino acids. In this study, we tried to identify the enzyme(s) responsible for the cleavage of deiminated filaggrin in vitro. First, we investigated citrulline aminopeptidase activity in the extract of newborn rat epidermis by double layer fluorescent zymography and detected strong activity at neutral pH. Monitoring the citrulline-releasing activity, we purified an enzyme of 280 kDa, comprised of six identical subunits of 48 kDa. The NH2 terminus of representative tryptic peptides perfectly matched the sequence of rat bleomycin hydrolase (BH). The enzyme released various amino acids except Pro from β-naphthylamide derivatives and hydrolyzed citrulline-β-naphthylamide most effectively. Thus, to break down deiminated filaggrin, another protease would be required. Among proteases tested, calpain I degraded the deiminated filaggrin effectively into many peptides of different mass on the matrix-assisted laser desorption/ionization-time of flight mass spectrum. We confirmed that various amino acids including citrulline were released by BH from those peptides. On the other hand, caspase 14 degraded deiminated filaggrin into a few peptides of limited mass. Immunohistochemical analysis of normal human skin revealed co-localization of BH and filaggrin in the granular layer. Collectively, our results suggest that BH is essential for the synthesis of natural moisturizing factors and that calpain I would play a role as an upstream protease in the degradation of filaggrin.

Keratinocytes synthesize enteropeptidase and multiple forms of trypsinogen during terminal differentiation.

Members of the trypsin-like and chymotrypsin-like kallikrein family are important in the desquamation process. In this study, we isolated cDNA clones encoding trypsinogen 4 (brain trypsinogen) and a previously unreported isoform of trypsinogen from a human keratinocyte cDNA library. The nucleotide sequence of the new isoform only differs from those of trypsinogen 3 (mesotrypsinogen) and trypsinogen 4 in an exon encoding the N-terminal region, indicating that this isoform is an alternative splicing variant of the mesotrypsinogen gene PRSS3. Both isoforms contained the sequence DDDDK-I, a putative cleavage site for activation by enteropeptidase. Thus, after activation, mesotrypsin would be produced. Immunohistochemical and in situ hybridization studies revealed that trypsinogens were expressed and localized in the upper epidermis, especially in the granular layer. In cultured keratinocytes, enteropeptidase mRNA was expressed at the confluent stage, and its expression was strongly upregulated after air exposure. Interestingly, it was synthesized and localized only at the granular layer, suggesting that the generation of active mesotrypsin is restricted to this layer. The enteropeptidase-cleavage product was also found at the same layer. When a skin equivalent model was cultured in the medium without air exposure, the cornified layer was not formed, and many cells expressed trypsinogens and enteropeptidase. Those cells were found to be TUNEL positive. Because mesotrypsin is resistant to naturally occurring trypsin inhibitors, confined expression of the isoforms of mesotrypsinogens and enteropeptidase may indicate that mesotrypsin is involved in keratinocyte terminal differentiation.

Quantification of activated and total caspase-14 with newly developed ELISA systems in normal and atopic skin

BACKGROUND Activation of caspase-14 occurs during terminal differentiation of keratinocytes and may play a role in filaggrin degradation. Therefore, down-regulation of caspase-14 may lead to impaired barrier function. OBJECTIVE To compare the levels of active and total caspase-14 in healthy subjects in various age groups and in patients with atopic dermatitis (AD), using two enzyme-linked immunoassay (ELISA) systems. METHODS We established four clones of monoclonal antibodies to caspase-14 and used clone 3 as the immobilizing antibody. A cleavage site-directed antibody, h14D146 [4] was used for specific quantification of active caspase-14 in extracts of tape-stripped corneocytes. Total caspase-14 was measured with a commercial antibody, H-99. RESULTS The amount of caspase-14 remained constant (ca. 0.1% of extractable proteins) in healthy males from their twenties to their fifties. Caspase-14 was mostly in active form (71-94%) in these extracts. In contrast, caspase-14 level and active caspase-14 ratio were significantly decreased in females in their fifties and sixties. Contents of free amino acids were decreased in females in their sixties, and transepidermal water loss was increased in females in their forties and sixties. In patients with AD, active caspase-14 was markedly down-regulated compared to age-matched controls in both lesional (7.5%) and non-lesional skin (10.6%). Staining of active caspase-14 was considerably weaker in non-lesional skin and was hardly detectable in lesional skin with parakeratosis. CONCLUSION Our new ELISA systems are effective tools to quantify activation of caspase-14. Our results indicate a role of caspase-14 in epidermal barrier function.

Kallikrein-related peptidase 5 functions in proteolytic processing of profilaggrin in cultured human keratinocytes

Background: Filaggrin is a skin barrier function-related factor processed from profilaggrin. The identity of human profilaggrin-processing enzymes remains unclear. Results: The protease kallikrein 5 (KLK5) specifically processed a recombinant human filaggrin fragment fused to a linker. Conclusion: KLK5 is potentially a key molecule in human profilaggrin maturation. Significance: KLK5 may function in formation of the skin barrier. Filaggrin protein is synthesized in the stratum granulosum of the skin and contributes to the formation of the human skin barrier. Profilaggrin is cleaved by proteolytic enzymes and converted to functional filaggrin, but its processing mechanism remains not fully elucidated. Kallikrein-related peptidase 5 (KLK5) is a major serine protease found in the skin, which is secreted from lamellar granules following its expression in the stratum granulosum and activated in the extracellular space of the stratum corneum. Here, we searched for profilaggrin-processing protease(s) by partial purification of epidermal extracts and found KLK5 as a possible candidate. We used high performance liquid chromatography coupled with electrospray tandem mass spectrometry to show that KLK5 cleaves profilaggrin. Furthermore, based on a proximity ligation assay, immunohistochemistry, and immunoelectron microscopy analysis, we reveal that KLK5 and profilaggrin co-localize in the stratum granulosum in human epidermis. KLK5 knockdown in normal cultured human epidermal keratinocytes resulted in higher levels of profilaggrin, indicating that KLK5 potentially functions in profilaggrin cleavage.

Bleomycin Hydrolase Is Regulated Biphasically in a Differentiation- and Cytokine-dependent Manner: RELEVANCE TO ATOPIC DERMATITIS

Loss-of-function mutation in the profilaggrin gene is a major risk factor for atopic dermatitis (AD). Previously, we showed that a neutral cysteine protease, bleomycin hydrolase (BH), has a role in generating natural moisturizing factors, and calpain I is an upstream protease in the filaggrin degradation pathway. Here, we investigated the transcriptional regulatory mechanisms of BH and the relevance of BH to AD. First, we cloned the 5′-flanking region of BH. Deletion analyses identified a critical region for BH promoter activity within −216 bp upstream. Electrophoretic mobility shift assay revealed that MZF-1, Sp-1, and interferon regulatory factor-1/2 could bind to this region in vitro. Moreover, site-directed mutagenesis of the MZF-1 and Sp-1 motifs markedly reduced BH promoter activity. These data indicate that BH expression is up-regulated via MZF-1 and Sp-1. Interestingly, a Th1 cytokine, IFN-γ, significantly reduced the expression of BH. Analyses with site-directed mutagenesis and small interference RNA supported the suppressing effect of IFN-γ on BH expression. On the other hand, a Th2 cytokine, IL-4, did not show any direct effect on BH expression. However, it down-regulated MZF-1 and Sp-1 in cultured keratinocytes, indicating that IL-4 could work as a suppressor in BH regulation. Lastly, we examined expression of BH in skins of patients with AD. BH activity and expression were markedly decreased in AD lesional skin, suggesting a defect of the filaggrin degradation pathway in AD. Our results suggest that BH transcription would be modulated during both differentiation and inflammation.

Kallikrein-related Peptidase-7 Regulates Caspase-14 Maturation during Keratinocyte Terminal Differentiation by Generating an Intermediate Form

Background: Caspase-14 activation is associated with keratinocyte terminal differentiation. Results: Kallikrein-related peptidase-7 (KLK7) generates an activation intermediate comprising 20- and 8-kDa subunits by cleavage after Tyr178 of procaspase-14. This intermediate cleaves procaspase-14 at Asp146, generating mature, active caspase-14. Conclusion: Caspase-14 maturation is mediated by KLK7 and an intermediate form of caspase-14. Significance: Caspase-14 has a unique activation mechanism. The maturation and activation mechanisms of caspases are generally well understood, except for those of caspase-14, which is activated at the onset of keratinocyte terminal differentiation. We investigated the possible involvement of epidermal proteases expressed in the late stage of differentiation, and found that the chymotrypsin-like serine protease kallikrein-related peptidase-7 (KLK7) cleaved procaspase-14 at Tyr178, generating an intermediate form that consists of a large (20 kDa) and a small subunit (8 kDa). We prepared an antibody directed to this cleavage site (h14Y178 Ab), and confirmed that it recognized a 20-kDa band formed when procaspase-14 was incubated with chymotrypsin or KLK7. We then constructed a constitutively active form of the intermediate, revC14-Y178. The substrate specificity of revC14-Y178 was completely different from that of caspase-14, showing broad specificity for various caspase substrates except WEHD-7-amino-4-trifluoromethylcoumarin (AFC), the preferred substrate of active, mature caspase-14. Km values for VEID-AFC, DEVD-AFC, LEVD-AFC, and LEHD-AFC were 0.172, 0.261, 0.504, and 0.847 μm, respectively. We confirmed that the mature form of caspase-14 was generated when procaspase-14 was incubated with KLK7 or revC14-Y178. Expression of constitutively active KLK7 in cultured keratinocytes resulted in generation of both the intermediate form and the mature form of caspase-14. Immunohistochemical analysis demonstrated that the intermediate form was localized at the granular layer. Our results indicate that regulation of procaspase-14 maturation during terminal differentiation is a unique two-step process involving KLK7 and an activation intermediate of caspase-14.

Effects of the gravitational vertical on the visual perception of reversible figures

We examined the effects of the gravitational vertical on the perception of reversible figures. Each reversible figure had two interpretations depending on whether it was viewed vertically in one orientation or upside down. When it was presented horizontally, the two interpretations alternated. Subjects were required to indicate which interpretation was perceived after briefly viewing the horizontal presentation on a head-mounted display. When the subject was upright, each interpretation occurred by chance. When the subject was lying on one side, the horizontal figure was generally perceived as if it was presented vertically with the side down. The results suggest that the perception of reversible figures is influenced by the gravitational vertical, which might be reconstructed by multimodal integration of vestibular, proprioceptive, and tactile inputs.

Identification of an S100A8 Receptor Neuroplastin-β and its Heterodimer Formation with EMMPRIN

We previously reported a positive feedback loop between S100A8/A9 and proinflammatory cytokines mediated by extracellular matrix metalloproteinase inducer, an S100A9 receptor. Here, we identify neuroplastin-β as an unreported S100A8 receptor. Neuroplastin-β and extracellular matrix metalloproteinase inducer form homodimers and a heterodimer, and they are co-localized on the surface of cultured normal human keratinocytes. Knockdown of both receptors suppressed cell proliferation and proinflammatory cytokine induction. Upon stimulation with S100A8, neuroplastin-β recruited GRB2 and activated extracellular signal-regulated kinase, resulting in keratinocyte proliferation. Keratinocyte proliferation in response to inflammatory stimuli was accelerated in involucrin promoter-driven S100A8 transgenic mice. Further, S100A8 and S100A9 were strongly up-regulated and co-localized in lesional skin of atopic dermatitis patients. Our results indicate that neuroplastin-β and extracellular matrix metalloproteinase inducer form a functional heterodimeric receptor for S100A8/A9 heterodimer, followed by recruitment of specific adaptor molecules GRB2 and TRAF2, and this signaling pathway is involved in activation of both keratinocyte proliferation and skin inflammation in atopic skin. Suppression of this pathway might have potential for treatment of skin diseases associated with chronic inflammation such as atopic dermatitis.

Discoid lupus erythematosus in a patient with scleroderma and hepatitis C virus infection

A 49-year-old Japanese woman presented with discoid lupus erythematosus (DLE) on the face. The presence of Raynaud’s phenomenon, swollen fingers, a high anti-nuclear antibody titer, and the results of a biopsy revealed limited-type systemic sclerosis (lSSc). The association of SSc with DLE is rare, although some single case reports have been published in Japan. Our patient was positive for hepatitis C virus infection. Racial predisposition and immune imbalance are proposed to have played a role in the development of these lesions in our case.

Plaque‐type cutaneous focal mucinosis

and electrolytes. BD is a multisystem disorder characterized by vasculitis. Colchicine and azathioprine have been used for mucocutaneous BD for a long time. However, when used over a long period of time, these drugs have serious side effects such as hepatic enzyme elevation, abdominal pain and pancytopenia. EC-MPS has a similar activity to those of immunosuppressive drugs but comparably few side effects. Mycophenolate mofetil was found to be ineffective in the treatment of mucocutaneous BD in a clinical trial. But in one case report, EC-MPS was found effective for refractory intestinal BD evaluated with enteroscopy. Treatment with EC-MPS in this group of patients with recalcitrant mucocutaneous BD leads to significant decrease in disease activity after six months of treatment in 10 patients. Moreover, side effects were mild and did not lead to discontinuation of therapy, but safety and recurrence rates need to be evaluated in a long-term follow-up study. Consequently, we suggest that new studies on MPS with other drugs will reveal new insights in treatment of mucocutaneous BD.