Efficient removal of black henna tattoos.

BACKGROUND/OBJECTIVES: Para-phenylenediamine, a dye frequently added to henna tattoos to create the black color, is a potent contact allergen. Severe contact dermatitis may arise within days even after the first application. Our objective was to develop a method for rapid and complete removal of para-phenylenediamine-containing black henna tattoos from the skin, an important problem many physicians are confronted with, but for which no simple method exists. METHODS: A database search revealed polyethylene glycol 400, described in removal of ortho-phenylenediamine from contaminated skin. We therefore investigated its use in removal of the structurally related ortholog para-phenylenediamine present in black henna tattoos. RESULTS: A protocol was established involving repeated cycles of rinsing of the skin with polyethylene glycol 400 solution. In 5 patients, one of whom had already developed a severe blistering contact dermatitis and another a mild erosive dermatitis, black henna tattoos were successfully removed. Removal was completed in a single session of 1 hour or less, depending on tattoo size, with a maximum of 6 rinse cycles. CONCLUSIONS: We provide a simple and safe method for rapid and effective removal of black henna tattoos. This procedure requires no special equipment and can be applied in virtually any setting.

Hereditary angioedema in a single family with specific mutations in both plasminogen and SERPING1 genes.

BACKGROUND: Hereditary angioedema (HAE) is a group of genetic diseases characterized by recurrent, painful and potentially lethal tissue swelling. The most common form results from mutations in the SERPING1 gene, leading to reduced function of complement 1 inhibitor (C1-INH). Rarer forms with normal C1-INH may arise from mutations in the coagulation factor F12 gene, but mostly the genetic background is unknown. Recently, a novel HAE mutation in the plasminogen (PLG) gene was shown. PATIENTS AND METHODS: We analyzed the various clinical manifestations of HAE in 14 related patients using clinical data, biochemical analysis for C1-INH and C4 as well as gene sequencing. RESULTS: Patients' symptoms were assigned to two different forms of HAE. In ten patients suffering from swelling of the lips or tongue but not of the extremities, a mutation in the PLG gene (c.988A>G) was found whereas in the only four patients with swelling of the gastrointestinal tract and extremities, a mutation in the SERPING1 gene (c.1480C>T) was identified. In two cases this was additional to PLG c.988A>G. CONCLUSIONS: This unique finding of two different HAE-specific mutations in a large family not only explains the divergent phenotypes but also supports a genotype-phenotype correlation showing that abdominal attacks and swelling of the extremities are common with HAE-C1-INH but unusual with HAE-PLG.

Peptide binding by catalytic domains of the protein disulfide isomerase-related protein ERp46.

The protein disulfide isomerase (PDI) family member ERp46/endoPDI/thioredoxin domain-containing protein 5 is preferentially expressed in a limited number of tissues, where it may function as a survival factor for nitrosative stress in vivo. It is involved in insulin production as well as in adiponectin signaling and interacts specifically with the redox-regulatory endoplasmic reticulum proteins endoplasmic oxidoreductin 1α (Ero1α) and peroxiredoxin-4. Here, we show that ERp46, although lacking a PDI-like redox-inactive b'-thioredoxin domain with its hydrophobic substrate binding site, is able to bind to a large pool of peptides containing aromatic and basic residues via all three of its catalytic domains (a(0), a and a'), though the a(0) domain may contain the primary binding site. ERp46, which shows relatively higher activity as a disulfide-reductase than as an oxidase/isomerase in vitro compared to PDI and ERp57, possesses chaperone activity in vivo, a property also shared by the C-terminal a' domain. A crystal structure of the a' domain is also presented, offering a view of possible substrate binding sites within catalytic domains of PDI proteins.

Crystal structure and functional analysis of the protein disulfide isomerase-related protein ERp29.

The protein disulfide isomerase-related protein ERp29 is a putative chaperone involved in processing and secretion of secretory proteins. Until now, however, both the structure and the exact nature of interacting substrates remained unclear. We provide for the first time a crystal structure of human ERp29, refined to 2.9 A, and show that the protein has considerable structural homology to its Drosophila homolog Wind. We show that ERp29 binds directly not only to thyroglobulin and thyroglobulin-derived peptides in vitro but also to the Wind client protein Pipe and Pipe-derived peptides, although it fails to process Pipe in vivo. A monomeric mutant of ERp29 and a D domain mutant in which the second peptide binding site is inactivated also bind protein substrates, indicating that the monomeric thioredoxin domain is sufficient for client protein binding. Indeed, the b domains of ERp29 or Wind, expressed alone, are sufficient for binding proteins and peptides. Interacting peptides have in common two or more aromatic residues, with stronger binding for sequences with overall basic character. Thus, the data allow a view of the two putative peptide binding sites of ERp29 and indicate that the apparent, different processing activity of the human and Drosophila proteins in vivo does not stem from differences in peptide binding properties.

A possible biochemical link between NADPH oxidase (Nox) 1 redox-signalling and ERp72.

Emerging evidence indicates that Nox (NADPH oxidase) 1-generated ROS (reactive oxygen species) play critical regulatory roles in various cellular processes, yet little is known of direct targets for the oxidase. In the present study we show that one of the proteins selectively oxidized in response to Nox1-generated ROS was ERp72 (endoplasmic reticulum protein 72 kDa) with TRX (thioredoxin) homology domains. Oxidation of ERp72 by Nox1 resulted in an inhibition of its reductase activity. EGF treatment of cells stimulated the Nox1 activity and the activated Nox1 subsequently mediated EGF-induced suppression of the ERp72 reductase activity. Co-immunoprecipitation, GST (glutathione transferase) pulldown assays and mutational analysis, indicated that Nox1 associates with ERp72, which involves its N-terminus encompassing a Ca(2+)-binding site and the first TRX-like motif. Furthermore, confocal microscopy showed co-localization between Nox1 and ERp72 at the plasma membrane. These results suggest that Nox1 functionally associates with ERp72, regulating redox-sensitive signalling pathways in a cellular context.

CD137 ligand reverse signaling has multiple functions in human dendritic cells during an adaptive immune response.

T cell activation via dendritic cells (DC) is an important step in the adaptive immune response, which requires DC maturation, migration to lymph nodes and presentation of antigen to T cells. CD137 receptor expressed on activated T cells is a potent costimulatory molecule. Here, we investigated the functions of CD137 ligand (CD137L) in human monocyte-derived DC during an immune response. Cross-linking of CD137L on DC leads to cell maturation in an autocrine fashion, mostly via release of TNF-alpha. Reverse signaling of CD137L also mediates migration of DC via up-regulation of the CCR7 chemokine receptor, demonstrated by an in vivo MIP-3beta-dependent SCID mouse migration model. Finally, CD137L-activated DC induce differentiation of human T cells into potent Th1 effectors. Cocultivation of autologous T cells and CD137L-activated DC in an antigen-specific reaction leads to T cell proliferation and the release of IL-12p70 and IFN-gamma. These findings deliver new insights into the multiple effects of reverse signaling of CD137L in human DC during the initiation of an adaptive immune response, including the key features of DC maturation, migration and, ultimately, antigen-specific T cell differentiation.

Endobrevin/VAMP8 mediates exocytotic release of hexosaminidase from rat basophilic leukaemia cells.

Mast cells are important players in innate immunity and mediate allergic responses. Upon stimulation, they release biologically active mediators including histamine, cytokines and lysosomal hydrolases. We used permeabilized rat basophilic leukaemia cells as model to identify R-SNAREs (soluble NSF (N-ethylmaleimide-sensitive fusion protein)) mediating exocytosis of hexosaminidase from mast cells. Of a complete set of recombinant mammalian R-SNAREs, only vesicle associated membrane protein (VAMP8)/endobrevin consistently blocked hexosaminidase release, which was also insensitive to treatment with clostridial neurotoxins. Thus, VAMP8, which also mediates fusion of late endosomes and lysosomes, plays a major role in hexosaminidase release, strengthening the view that mast cell granules share properties of both secretory granules and lysosomes.

Conserved structural and functional properties of D-domain containing redox-active and -inactive protein disulfide isomerase-related protein chaperones.

The structure and mode of binding of the endoplasmic reticulum protein disulfide isomerase-related proteins to their substrates is currently a focus of intensive research. We have recently determined the crystal structure of the Drosophila melanogaster protein disulfide isomerase-related protein Wind and have described two essential substrate binding sites within the protein, one within the thioredoxin b-domain and another within the C-terminal D-domain. Although a mammalian ortholog of Wind (ERp29/28) is known, conflicting interpretations of its structure and putative function have been postulated. Here, we have provided evidence indicating that ERp29 is indeed similar in both structure and function to its Drosophila ortholog. Using a site-directed mutagenesis approach, we have demonstrated that homodimerization of the b-domains is significantly reduced in vitro upon replacement of key residues at the predicted dimerization interface. Investigation of Wind-ERp29 fusion constructs showed that mutants of the D-domain of ERp29 prevent transport of a substrate protein (Pipe) in a manner consistent with the presence of a discrete, conserved peptide binding site in the D-domain. Finally, we have highlighted the general applicability of these findings by showing that the D-domain of a redox-active disulfide isomerase, from the slime mold Dictyostelium discoideum, can also functionally replace the Wind D-domain in vivo.

Structural elucidation of the PDI-related chaperone Wind with the help of mutants.

The structures of the PDI-related protein Wind (with a C-terminal His(6) tag) and the mutants Y53S, Y53F and Y55K have been determined and compared with the wild-type structure with the His(6) tag at the N-terminus. All five structures show the same mode of dimerization, showing that this was not an artefact introduced by the nearby N-terminal His(6) tag and suggesting that this dimer may also be the biologically active form. Although the mutants Y53S and Y55K completely abrogate transport of the protein Pipe (which appears to be the primary function of Wind in the cell), only subtle differences can be seen in the putative Pipe-binding region. The Pipe binding in the active forms appears to involve hydrophobic interactions between aromatic systems, whereas the inactive mutants may be able to bind more strongly with the help of hydrogen bonds, which could disturb the delicate equilibrium required for effective Pipe transport.

Mapping of a substrate binding site in the protein disulfide isomerase-related chaperone wind based on protein function and crystal structure.

The protein disulfide isomerase (PDI)-related protein Wind is essential in Drosophila melanogaster, and is required for correct targeting of Pipe, an essential Golgi transmembrane 2-O-sulfotransferase. Apart from a thioredoxin fold domain present in all PDI proteins, Wind also has a unique C-terminal D-domain found only in PDI-D proteins. Here, we show that Pipe processing requires dimeric Wind, which interacts directly with the soluble domain of Pipe in vitro, and we map an essential substrate binding site in Wind to the vicinity of an exposed cluster of tyrosines within the thioredoxin fold domain. In vitro, binding occurs to multiple sites within the Pipe polypeptide and shows specificity for two consecutive aromatic residues. A second site in Wind, formed by a cluster of residues within the D-domain, is likewise required for substrate processing. This domain, expressed separately, impairs Pipe processing by the full-length Wind protein, indicating competitive binding to substrate. Our data represent the most accurate map of a peptide binding site in a PDI-related protein available to date and directly show peptide specificity for a naturally occurring substrate.

Crystal structure and functional analysis of Drosophila Wind, a protein-disulfide isomerase-related protein.

In the developing Drosophila melanogaster embryo, dorsal-ventral patterning displays an absolute requirement for the product of the essential windbeutel gene, Wind. In homozygous windbeutel mutant flies, dorsal-ventral patterning fails to initiate because of the failure of the Golgi-resident proteoglycan-modifying protein, Pipe, to exit the endoplasmic reticulum, and this leads to the death of the embryo. Here, we describe the three-dimensional structure of Wind at 1.9-A resolution and identify a candidate surface for interaction with Pipe. This represents the first crystal structure of a eukaryotic protein-disulfide isomerase-related protein of the endoplasmic reticulum to be described. The dimeric protein is composed of an N-terminal thioredoxin domain and a C-terminal alpha-helical domain unique to protein-disulfide isomerase D proteins. Although Wind carries a CXXC motif that is partially surface accessible, this motif is redox inactive, and the cysteines are not required for the targeting of Pipe to the Golgi. However, both domains are required for targeting Pipe to the Golgi, and, although the mouse homologue ERp28 cannot replace the function of Wind, exchange of the Wind D-domain with that of ERp28 allows for efficient Golgi transport of Pipe.