Generalized dominant epidermolysis bullosa simplex: decreased activity of a gelatinolytic protease in cultured fibroblasts as a phenotypic marker

Pancreatic trypsin activates human promatrix metalloproteinase-2

In contrast to the prevalent view in the literature hitherto, the present study shows that pancreatic trypsin can activate human promatrix metalloproteinase-2 (proMMP-2). It is shown that trypsin's ability to activate proMMP-2 is dependent on various environmental factors such as the level of exogenously added Ca(2+) and Brij-35, temperature, as well as trypsin concentration. The activation occurred as a sequential processing of the proenzyme, initially generating an active 62kDa species. This was followed by successive truncation of the C-terminal domain, giving rise to active species of 56kDa, 52kDa and 50kDa. Tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) prevented the trypsin-mediated C-terminal truncation, without affecting the generation of the 62kDa species, while the presence of EDTA increased the rate of the trypsin-mediated activation of proMMP-2. MALDI-TOF MS analysis of the 50kDa form indicated that trypsin generated active forms with either Lys87 or Trp90 as the N-terminal residue and Arg538 as a C-terminal residue. The trypsin-activated MMP-2 was active in solution against both synthetic and physiologic substrates, and the steady-state kinetic coefficients k(cat), K(m) and k(cat)/K(m) were determined for the enzyme activated either by APMA, membrane-type 1 matrix metalloproteinase (MT1-MMP) or trypsin. The trypsin-activated MMP-2 exhibited slightly lower k(cat) and k(cat)/K(m) values as well as a slightly higher K(i) value against TIMP-1 compared to the enzyme activated by APMA or MT1-MMP. Docking studies of TIMP-1 revealed that the slightly weaker binding of the inhibitor to the trypsin-activated MMP-2 could be attributed to its shorter N terminus (Lys87/Trp90 versus Tyr81), as Phe83 and Arg86 interacted directly with the inhibitor. Our results suggest that the trypsin-activated MMP-2 possesses the catalytic and regulatory potential to be of significance in vivo.

The cytoskeleton and disease: genetic disorders of intermediate filaments

Specialized cytoskeletons play many fascinating roles, including mechanical integrity and wound-healing in epidermal cells, cell polarity in simple epithelia, contraction in muscle cells, hearing and balance in the inner ear cells, axonal transport in neurons, and neuromuscular junction formation between muscle cells and motor neurons. These varied functions are dependent upon cytoplasmic networks of actin microfilaments (6 nm), intermediate filaments (10 nm) and microtubules (23 nm), and their many associated proteins. In this chapter, I review what is known about the cytoskeletons of intermediate filaments and their associated proteins. I focus largely on epidermal cells, which devote most of their protein-synthesizing machinery to producing an extensive intermediate filament network composed of keratin. Recent studies have shown that many of the devastating human disorders that arise from degeneration of this cell type have as their underlying basis either defects in the genes encoding keratins or abnormalities in keratin IF networks. I discuss what we know about the functions of IFs, and how the link to genetic disease has enhanced this understanding.

Anchoring fibrils, collagen VII, and neutral metalloproteases in recessive dystrophic epidermolysis bullosa inversa

Structure of the anchoring fibrils, expression of collagen VII, and gelatinolytic activity in skin fibroblasts were assessed in six patients with epidermolysis bullosa dystrophica (EBD) inversa and in control groups consisting of probands with other EBD subtypes and healthy individuals. All six patients with EBD inversa, as well as the patients with generalized non-mutilating and localized EBD, showed positive staining with antibodies to collagen VII, the major anchoring fibril protein. Four patients with severe generalized mutilating EBD exhibited negative staining. Ultrastructurally, normal anchoring fibrils were demonstrable in uninvolved skin of patients with localized, inversa, and generalized non-mutilating subtypes. At the same time, a high degree of variability was observed in the amount and quality of anchoring fibrils in the various stages of lesional skin, including co-existence of normal and partially degraded anchoring fibrils. Of all 12 patients only one localized and two inversa cases showed an increased gelatinolytic activity in vitro. However, the high activity was associated with neither the severity of the disease nor the inversa subtype. In addition, intact collagen VII could be extracted from the dermis of one inversa patient. The present data show no correlation between increased in vitro gelatinolytic activity and abnormalities of the anchoring fibrils or collagen VII in skin of patients with recessive EBD, and therefore suggest molecular heterogeneity of the causative pathogenetic mechanisms.

Epidermolysis bullosa simplex: expression of gelatinase activity in cultured human skin fibroblasts

We have measured the baseline level of gelatinase in fibroblast-conditioned medium from 41 Scandinavian individuals. They comprised 12 healthy persons, 11 individuals with the skin disorder dominant epidermolysis bullosa simplex (DEBS), 16 patients with other types of epidermolysis bullosa (EB) and 2 siblings with prolidase deficiency. These results divide the cell strains into those with low and those with high activity levels. Although this dual biochemical trait occurred in all the groups of individuals, the high-activity trait was more frequent among the DEBS patients. The localized DEBS forms showed an elevated activity level, in contrast to the previously reported generalized DEBS Köbner forms. Although a high level was found in some individuals with other EB forms, the high incidence in four families with localized DEBS Weber-Cockayne (eight of eight) and a single family with generalized DEBS--mottled pigmentation (two of two) may result from a close linkage between an EB gene and a gene responsible for the biochemical trait. In addition, in the single complete family tested, the level of gelatinase activity in cultured fibroblasts seemed to be regulated by codominant alleles or genes. A raised baseline level of gelatinase activity in cultured skin fibroblasts may be the result of either an altered expression of gelatinase or an allelic variant of this enzyme with increased specific activity. Further studies of gelatinase in cultured fibroblasts may provide insight into the regulatory mechanism and genetics behind this activity and allow formal linkage studies versus DEBS.

Head and neck manifestations of epidermolysis bullosa

Although considerable attention has focused on the pathophysiology and external dermatologic consequences of epidermolysis bullosa (EB), head and neck mucosal manifestations pose specific management problems. The otolaryngologic aspects of EB, with emphasis on involvement and treatment of the ears, oral cavity and teeth, larynx and trachea, and pharynx and esophagus, are reviewed. Guidelines are presented for specialized dental, anesthetic, and nutritional management in patients with this potentially fatal disease.

A function for keratins and a common thread among different types of epidermolysis bullosa simplex diseases

Previously we demonstrated that transgenic mice expressing a mutant keratin in the basal layer of their stratified squamous epithelia exhibited a phenotype bearing resemblance to a subclass (Dowling Meara) of a heterogeneous group of human skin disorders known as epidermolysis bullosa simplex (EBS) (Vassar, R., P. A. Coulombe, L. Degenstein, K. Albers, E. Fuchs. 1991. Cell. 64:365-380.). The extent to which subtypes of EBS diseases might be genetically related is unknown, although they all exhibit skin blistering as a consequence of basal cell cytolysis. We have now examined transgenic mice expressing a range of keratin mutants which perturb keratin filament assembly to varying degrees. We have generated phenotypes which include most subtypes of EBS, demonstrating for the first time that at least in mice, these diseases can be generated by different mutations within a single gene. A strong correlation existed between the severity of the disease and the extent to which the keratin filament network was disrupted, implicating perturbations in keratin networks as an essential component of these diseases. Some keratin mutants elicited subtle perturbations, with no signs of the tonofilament clumping typical of Dowling-Meara EBS and our previous transgenic mice. Importantly, basal cell cytolysis still occurred, thereby uncoupling cytolysis from the generation of large, insoluble cytoplasmic protein aggregates. Moreover, cell rupture occurred in a narrowly defined subnuclear zone, and seemed to involve three factors: (a) filament perturbation, (b) the columnar shape of the basal cell, and (c) physical trauma. This work provides the best evidence to date for a structural function of a cytoplasmic intermediate filament network, namely to impart mechanical integrity to the cell in the context of its tissue.

Point mutations in human keratin 14 genes of epidermolysis bullosa simplex patients: genetic and functional analyses

Previously we demonstrated that transgenic mice expressing mutant basal epidermal keratin genes exhibited a phenotype resembling a group of autosomal dominant human skin disorders known as epidermolysis bullosa simplex (EBS). EBS diseases affect approximately 1: 50,000 and are of unknown etiology, although all subtypes exhibit blistering arising from basal cell cytolysis. We now demonstrate that two patients with spontaneous cases of Dowling-Meara EBS have point mutations in a critical region in one (K14) of two basal keratin genes. To demonstrate function, we engineered one of these point mutations in a cloned human K14 cDNA, and showed that a K14 with an Arg-125----Cys mutation disrupted keratin network formation in transfected keratinocytes and perturbed filament assembly in vitro. Since we had previously shown that keratin network perturbation is an essential component of EBS diseases, these data suggest that the basis for the phenotype in this patient resides in this point mutation.

Blistering disorders in childhood

Many conditions present in childhood with vesicles and bullae, ranging from benign conditions to life-threatening diseases. This article reviews selected blistering disorders, with emphasis on new information that is helpful to the practicing physician. Entities that are discussed in this article include childhood zoster and fetal varicella syndrome, urticaria pigmentosa, scabies, bullous bug bites, lichen sclerosus et atrophicus, epidermolysis bullosa, and erythema multiforme.

Mutant keratin expression in transgenic mice causes marked abnormalities resembling a human genetic skin disease

To explore the relationship between keratin gene mutations and genetic disease, we made transgenic mice expressing a mutant keratin in the basal layer of their stratified squamous epithelia. These mice exhibited abnormalities in epidermal architecture and often died prematurely. Blistering occurred easily, and basal cell cytolysis was evidence at the light and electron microscopy levels. Keratin filament formation was markedly altered, with keratin aggregates in basal cells. In contrast, terminally differentiating cells made keratin filaments and formed a stratum corneum. Recovery of outer layer cells was attributed to down-regulation of mutant keratin expression and concomitant induction of differentiation-specific keratins as cells terminally differentiate, and the fact that these cells arose from basal cells developing at a time when keratin expression was relatively low. Collectively, the pathobiology and biochemistry of the transgenic mice and their cultured keratinocytes bore a resemblance to a group of genetic disorders known as epidermolysis bullosa simplex.

Epidermolysis bullosa

During the last 10 years, there has been considerable progress in the knowledge of epidermolysis bullosa, which has led to recognition of at least 18 different varieties. This review article attempts to classify these varieties and to emphasize the orodental findings in patients with epidermolysis bullosa.

Abnormal binding of lectin to the epidermal cell membranes in the skin of epidermolysis bullosa simplex

Epidermolysis bullosa (EB) simplex is a congenital disease that has blister formation following minor mechanical trauma to the skin. However, the least amount of information concerning the pathogenesis is known in this condition. One possibility is that there are structural abnormalities in epidermal cell membranes. In the present study, we examined the binding of lectins to epidermal cell membranes by ABC method. Biopsy skin specimens were obtained from patients with simplex, junctional and dystrophic forms of EB, and normal volunteers. In the case of EB simplex, the cell membranes of keratinocytes in the basal and spinous cell layers did not bind to soybean agglutinin in specimens from blister edges or mechanical traumatized areas. No differences were found in binding pattern between the other forms of EB and normal controls. This results suggest the presence of structural abnormalities in epidermis of EB simplex.

Gelatinase expression in generalized epidermolysis bullosa simplex fibroblasts

The use of gelatinase expression in dermal fibroblast cultures as a marker for generalized epidermolysis bullosa simplex (D-EBS-Köbner) has been tested. None of the 6 Köbner patients tested (from 3 families) produced reduced amounts of gelatinase compared with their healthy relatives and other control groups. This shows that a reduced production of gelatinase from dermal fibroblasts is not uniformly a marker for D-EBS-K.

Epidermolysis bullosa: a review

Epidermolysis bullosa is a group of inherited disorders characterized by blistering of the skin as a result of minor trauma. The disease can be divided into three anatomical categories: Epidermolytic, where blister cleavage occurs within the epidermis; Junctional, which has blister cleavage within the lamina lucida; and Dermolytic, where blister cleavage occurs below the basal lamina in the upper papillary dermis. Each of these three categories can be divided into several distinct entities based on clinical and histologic criteria. Basic biochemical studies have increased our understanding of several of these diseases, most notably recessive dystrophic epidermolysis bullosa. Although therapy for patients with EB is largely supportive, increased knowledge of the biochemistry of these disorders is making direct therapeutic interventions possible.