Hailey-Hailey disease is caused by mutations in ATP2C1 encoding a novel Ca(2+) pump

PMR1/SPCA Ca2+ pumps and the role of the Golgi apparatus as a Ca2+ store

Besides the well-known sarco/endoplasmic-reticulum Ca(2+)-transport ATPases (SERCA), animal cells contain a much less characterized P-type Ca(2+)-transport ATPase: the PMR1/SPCA Ca(2+)/Mn(2+)-transport ATPase. SPCA is mainly targeted to the Golgi apparatus. Phylogenetic analysis indicates that it might be more closely related to a putative ancestral Ca(2+) pump than SERCA. SPCA supplies the Golgi apparatus, and possibly other more distal compartments of the secretory pathway, with the Ca(2+) and Mn(2+) necessary for the production and processing of secretory proteins. In the lactating mammary gland, SPCA appears to be the primary pump responsible for supplementing the milk with high (60-100 mM) Ca(2+). It could also play a role in detoxification of cells overloaded with Mn(2+). Mutations in the human gene encoding the SPCA pump ( ATP2C1) result in Hailey-Hailey disease, a keratinocyte disorder characterized by incomplete cell adhesion. Recent observations show that the Golgi apparatus can function as a Ca(2+) store, which can be involved in setting up cytosolic Ca(2+) oscillations.

[Disseminated M. Hailey-Hailey]

Along with the typical intertriginous localization of Hailey-Hailey disease, generalized cutaneous involvement may also occur. Besides nonspecific triggers, genetic factors are considered to be responsible. Mutations of the ATP2C1 gene have been identified as causative factors in this genetic disease. No direct genotype-phenotype correlation between a specific mutation and the disseminated variant of Hailey-Hailey disease has been demonstrated.

Glycopeptide export from the endoplasmic reticulum into cytosol is mediated by a mechanism distinct from that for export of misfolded glycoprotein

When glycoproteins formed in the endoplasmic reticulum (ER) are misfolded, they are generally translocated into the cytosol for ubiquitination and are subsequently degraded by the proteasome. This system, the so-called ER-associated glycoprotein degradation, is important for eukaryotes to maintain the quality of glycoproteins generated in the ER. It has been established in yeast that several distinct proteins are involved in this translocation and degradation processes. Small glycopeptides formed in the ER are exported to the cytosol in a similar manner. This glycopeptide export system is conserved from yeast to mammalian cells, suggesting its basic biological significance for eukaryotic cells. These two export systems (for misfolded glycoproteins and glycopeptides) share some properties, such as a requirement for ATP and involvement of Sec61p, a central membrane protein presumably forming a dislocon channel for export of proteins. However, the machinery of glycopeptide export is poorly understood. In this study, various mutants known to have an effect on export/degradation of misfolded glycoproteins were examined for glycopeptide export activity with a newly established assay method. Surprisingly, most of the mutants were found not to exhibit a defect in glycopeptide export. The only gene that was found to be required on efficient export of both types of substrates was PMR1, the gene encoding the medial-Golgi Ca(2+)/Mn(2+)-ion pump. These results provide evidence that although the systems involved in export of misfolded glycoproteins and glycopeptides share some properties, they have exhibited distinct differences.

Molecular physiology of the SERCA and SPCA pumps

Intracellular Ca(2+)-transport ATPases exert a pivotal role in the endoplasmic reticulum and in the compartments of the cellular secretory pathway by maintaining a sufficiently high lumenal Ca(2+) (and Mn(2+)) concentration in these compartments required for an impressive number of vastly different cell functions. At the same time this lumenal Ca(2+) represents a store of releasable activator Ca(2+) controlling an equally impressive number of cytosolic functions. This review mainly focuses on the different Ca(2+)-transport ATPases found in the intracellular compartments of mainly animal non-muscle cells: the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) pumps. Although it is not our intention to treat the ATPases of the specialized sarcoplasmic reticulum in depth, we can hardly ignore the SERCA1 pump of fast-twitch skeletal muscle since its structure and function is by far the best understood and it can serve as a guide to understand the other members of the family. In a second part of this review we describe the relatively novel family of secretory pathway Ca(2+)/Mn(2+) ATPases (SPCA), which in eukaryotic cells are primarily found in the Golgi compartment.

Selective effects of calcium chelators on anterograde and retrograde protein transport in the cell

Calcium plays a regulatory role in several aspects of protein trafficking in the cell. Both vesicle fusion and vesicle formation can be inhibited by the addition of calcium chelators. Because the effects of calcium chelators have been studied predominantly in cell-free systems, it is not clear exactly which transport steps in the secretory pathway are sensitive to calcium levels. In this regard, we have studied the effects of calcium chelators on both anterograde and retrograde protein transport in whole cells. Using both cytochemical and biochemical analyses, we find that the anterograde-directed exit of vesicular stomatitis virus G protein and the retrograde-directed exit of Shiga toxin from the Golgi apparatus are both inhibited by calcium chelation. The exit of vesicular stomatitis virus G from a pre-Golgi compartment and the exit of Shiga toxin from an endosomal compartment are sensitive to the membrane-permeant calcium chelator 1,2-bis(2-amino phenoxy)ethane-N,N,N',N'-tetraacetic acid-tetrakis (acetoxymethyl ester) (BAPTA-AM). By contrast, endoplasmic reticulum exit and endocytic internalization from the plasma membrane are not affected by BAPTA. Together, our data show that some, but not all, trafficking steps in the cell may be regulated by calcium. These studies provide a framework for a more detailed analysis of the role of calcium as a regulatory agent during protein transport.

Ca(2+) regulation in differentiating lens cells in culture

In the ocular lens, cataract formation is associated with an elevated intracellular Ca(2+) concentration (Ca(2+)(i)) resulting from the loss of lens cell Ca(2+) regulation. The mechanisms regulating Ca(2+)(i) have been characterized previously in lens epithelial cells, but have not been well characterized in the more differentiated lens fiber cells. The mechanisms regulating Ca(2+)(i) in clusters of fiber-like cells (lentoids) in a sheep lens primary cell culture system in which the epithelial cells differentiate into enlarged fiber-like cells were investigated. Only approximately 50% of the lentoids responded to thapsigargin and/or agonists (ATP and epinephrine), compared to>95% of the epithelial cells. Remarkably, most (90%) lentoids exhibited a resting cytosolic Ca(2+)(i) that was approximately three-fold greater than that in epithelial cells (approximately 100n M). This elevated resting cytosolic Ca(2+)(i) was not affected by thapsigargin treatment, but decreased upon removal of extracellular Ca(2+) or addition of the Ca(2+) channel blocker Gd(3+) (5mM ). These results suggest that a plasma membrane Ca(2+) channel is more active in lentoids than in epithelial cells. Indeed, when plasma membrane cation channel activity was monitored by Mn(2+) influx and quenching of fura-2 fluorescence, quenching was faster in lentoids than epithelial cells. Following thapsigargin treatment, capacitative Ca(2+) entry was activated in epithelial cells but not lentoids. In conclusion, during differentiation in primary cell culture, lens cells lose their ability to respond to agonists and exhibit an elevated resting Ca(2+)(i) that was dependent on the activation of a Ca(2+) influx pathway. The results of this study support the possibility that a sustained elevation in resting Ca(2+)(i) is one of the factors controlling lens cell differentiation, possibly by triggering events such as calpain activation.

Mutation analysis of ATP2C1 gene in Taiwanese patients with Hailey-Hailey disease

BACKGROUND

Hailey-Hailey disease (HHD) is an autosomal dominant disorder with recurrent eruption of vesicles and bullae involving predominantly the neck, groin and axillary regions. Histopathology shows suprabasal cleavage in epidermal cells. Recent studies have revealed that HHD is caused by mutations in the ATP2C1 gene encoding a novel Ca2+ pump.

OBJECTIVES

To analyse the mutations of the ATP2C1 gene in Taiwanese patients with HHD.

METHODS

In total, five familial and two sporadic cases of HHD were retrieved from the medical records. The diagnosis of HHD was made based on the characteristic clinical features and histopathological evidence. All 27 exons and flanking intron boundaries were amplified by polymerase chain reaction and products analysed by direct sequencing.

RESULTS

We identified six novel mutations and one reported mutation: three deletion mutations (nt884-904del, 1459delCTCA, 1975delA), two non-sense mutations (R39X, R783X), one mis-sense mutation (A730T) and one splicing mutation (483 + 2T-->A). The non-sense mutation R39X had been reported previously; the other six mutations are novel mutations.

CONCLUSIONS

These results demonstrate that a spectrum of ATP2C1 gene mutations is present in Taiwanese HHD patients.

Functional expression in yeast of the human secretory pathway Ca(2+), Mn(2+)-ATPase defective in Hailey-Hailey disease

The discovery and biochemical characterization of the secretory pathway Ca(2+)-ATPase, PMR1, in Saccharomyces cerevisiae, has paved the way for identification of PMR1 homologues in many species including rat, Caenorhabditis elegans, and Homo sapiens. In yeast, PMR1 has been shown to function as a high affinity Ca(2+)/Mn(2+) pump and has been localized to the Golgi compartment where it is important for protein sorting, processing, and glycosylation. However, little is known about PMR1 homologues in higher organisms. Loss of one functional allele of the human gene, hSPCA1, has been linked to Hailey-Hailey disease, characterized by skin ulceration and improper keratinocyte adhesion. We demonstrate that expression of hSPCA1 in yeast fully complements pmr1 phenotypes of hypersensitivity to Ca(2+) chelators and Mn(2+) toxicity. Similar to PMR1, epitope-tagged hSPCA1 also resides in the Golgi when expressed in yeast or in chinese hamster ovary cells. (45)Ca(2+) transport by hSPCA1 into isolated yeast Golgi vesicles shows an apparent Ca(2+) affinity of 0.26 microm, is inhibitable by Mn(2+), but is thapsigargin-insensitive. In contrast, heterologous expression of vertebrate sarcoplasmic reticulum and plasma membrane Ca(2+)-ATPases in yeast complement the Ca(2+)- but not Mn(2+)-related phenotypes of the pmr1-null strain, suggesting that high affinity Mn(2+) transport is a unique feature of the secretory pathway Ca(2+)-ATPases.

Hailey-Hailey disease: molecular and clinical characterization of novel mutations in the ATP2C1 gene

Hailey-Hailey disease is an autosomal dominant skin disorder characterized by suprabasal cell separation (acantholysis) of the epidermis. Mutations in ATP2C1, the gene encoding a novel, P-type Ca2+-transport ATPase, were recently found to cause Hailey-Hailey disease. In this study, we used conformation-sensitive gel electrophoresis to screen all 28 translated exons of ATP2C1 in 24 Hailey-Hailey disease families and three sporadic cases with the disorder. We identified 22 different mutations, 18 of which have not previously been reported, in 25 probands. The novel mutations comprise three nonsense, six insertion/deletion, three splice-site, and six missense mutations and are distributed throughout the ATP2C1 gene. Six mutations were found in multiple families investigated here or in our previous study. Haplotype analysis revealed that two of these are recurrent mutations that have not been inherited from a common ancestor. Comparison between genotype and phenotype in 23 families failed to yield any clear correlation between the nature of the mutation and clinical features of Hailey-Hailey disease. The extensive interfamilial and intrafamilial phenotypic variability observed suggests that modifying genes and/or environmental factors may greatly influence the clinical features of this disease.

Mutations of ATP2C1 in Japanese patients with Hailey-Hailey disease: intrafamilial and interfamilial phenotype variations and lack of correlation with mutation patterns

We report herein mutations of ATP2C1 in 11 Japanese patients with Hailey-Hailey disease gene (including five previously reported) and compare the mutation pattern with clinical phenotypes. Patients with missense mutations and some of those with mutations causing premature termination showed erythema and erosions primarily at intertriginous areas. In two families with unique mutations, one with an in-frame three amino acid deletion plus an eight amino acid insertion and one with a two base pair deletion predicted to cause premature truncation, some affected individuals had unique clinical features -- generalization of Hailey-Hailey disease and generalized skin eruption resembling keratotic papules in Darier's disease -- but other affected individuals did not, suggesting the presence of severe intrafamilial phenotype variations. Our findings suggest that differences in clinical phenotypes are probably related to factors other than the type of causative mutation.

Intracutaneous botulinum toxin A versus ablative therapy of Hailey-Hailey disease--a case report

BACKGROUND

Hailey-Hailey disease is an autosomal-dominant blistering disease affecting the intertriginous skin. Dermabrasion and ablative laser treatment are known to be curative. Sweating is a common aggravating factor. Botulinum toxin A (BTXA) has been shown to inhibit sudoriferic nerves.

OBJECTIVE

To evaluate whether a treatment with BTXA induces remissions and can compete with ablative therapy. To compare dermabrasion with erbium:YAG laser therapy.

METHOD

Case report with side-by-side comparison. We used intracutaneous BTXA on both sides of the submammary region. Four days later a limited area of 25 cm(2) on each side was treated with either dermabrasion or erbium:YAG laser. The follow-up was 12 months.

RESULTS

Wound healing was complete within 7 days after erbium:YAG laser and two weeks after dermabrasion. Areas treated with BTXA alone also showed complete remission within two weeks. During a follow-up, no relapse occurred with either treatment.

CONCLUSION

BTXA is capable of inducing remissions of Hailey-Hailey disease without abrasion for at least 12 months. Among ablative treatments, erbium: YAG laser therapy leads to a more rapid wound closure than dermabrasion, with both causing complete remissions.

Molecular genetics of Ca(2+) stores and intracellular Ca(2+) signalling

An increasing number of studies based on recombinant cells and on mouse models that express an altered repertoire of some of the key components of the intracellular Ca(2+) release stores are becoming available as a result of molecular genetics techniques. Information from these studies, together with results from studies of human diseases caused by mutations in genes that encode proteins of the intracellular Ca(2+) stores, are providing a significant advancement in understanding the interactive nature of the molecular machinery that underlies intracellular Ca(2+) signalling and how the different components of the Ca(2+) stores contribute to the regulation of cellular functions.

Desmosomes: structure and function in normal and diseased epidermis

Desmosomes are important epidermal adhesion complexes that are characterized by a cell-specific expression of transmembrane cadherins and plaque-associated molecules. Desmosomes have so far, been implicated in three main disease types: autoimmune diseases that involve desmosome components (such as pemphigus vulgaris and pemphigus foliaceus), congenital diseases that affect intracellular calcium channels (such as Hailey-Hailey disease and Darier disease) and congenital diseases that directly affect desmosomal structural components. The identification of the first congenital defect affecting a desmosome component was in the gene for plakophilin I which caused an autosomal recessive skin fragility-ectodermal dysplasia syndrome with skin, hair and nail defects. Subsequently, either a haploinsufficiency of desmoplakin or a defect in desmoglein 1 was found to underlie the autosomal dominant condition Striate Palmoplantar Keratoderma. In addition, plakoglobin has been shown to be defective in Naxos disease, which results in a cardiomyopathy and growth of abnormal hair. These findings pave the way for the discovery of further cell cohesion-related diseases and will help to greatly increase our understanding of the specific function of desmosome and other epithelial junction components.

The Golgi PMR1 P-type ATPase of Caenorhabditis elegans. Identification of the gene and demonstration of calcium and manganese transport

In recent years, it has been well established that the Ca(2+) concentration in the lumen of intracellular organelles is a key determinant of cell function. Despite the fact that essential functions of the Golgi apparatus depend on the Ca(2+) and Mn(2+) concentration in its lumen, little is known on the transport system responsible for ion accumulation. The Golgi ion pump PMR1 has been functionally studied only in yeast. In humans, mutations in the orthologous gene ATP2C1 cause Hailey-Hailey disease. We report here the identification of the PMR1 homologue in the model organism Caenorhabditis elegans and after ectopic expression the direct study of its ion transport in permeabilized COS-1 cells. The C. elegans genome is predicted to contain a single PMR1 orthologue on chromosome I. We found evidence for alternative splicing in the 5'-untranslated region, but no indication for the generation of different protein isoforms. C. elegans PMR1 overexpressed in COS-1 cells transports Ca(2+) and Mn(2+) with high affinity into the Golgi apparatus in a thapsigargin-insensitive manner. Part of the accumulated Ca(2+) can be released by inositol 1,4,5-trisphosphate, in agreement with the idea that the Golgi apparatus is an inositol 1,4,5-trisphosphate-sensitive Ca(2+) store.

Spectrum of dominant mutations in the desmosomal cadherin desmoglein 1, causing the skin disease striate palmoplantar keratoderma

The adhesive proteins of the desmosome type of cell junction consist of two types of cadherin found exclusively in that structure, the desmogleins and desmocollins, coded by two closely linked loci on human chromosome 18q12.1. Recently we have identified a mutation in the DSG1 gene coding for desmoglein 1 as the cause of the autosomal dominant skin disease striate palmoplantar keratoderma (SPPK) in which affected individuals have marked hyperkeratotic bands on the palms and soles. In the present study we present the complete exon-intron structure of the DSG1 gene, which occupies approximately 43 kb, and intron primers sufficient to amplify all the exons. Using these we have analysed the mutational changes in this gene in five further cases of SPPK. All were heterozygotic mutations in the extracellular domain leading to a truncated protein, due either to an addition or deletion of a single base, or a base change resulting in a stop codon. Three mutations were in exon 9 and one in exon 11, both of which code for part of the third and fourth extracellular domains, and one was in exon 2 coding for part of the prosequence of this processed protein. This latter mutation thus results in the mutant allele synthesising only 25 amino acid residues of the prosequence of the protein so that this is effectively a null mutation implying that dominance in the case of this mutation was caused by haploinsufficiency. The most severe consequences of SPPK mutations are in regions of the body where pressure and abrasion are greatest and where desmosome function is most necessary. SPPK therefore provides a very sensitive measure of desmosomal function.

Cloning and characterization of human WDR10, a novel gene located at 3q21 encoding a WD-repeat protein that is highly expressed in pituitary and testis

Members of the steroid-thyroid-retinoid receptor superfamily regulate a spectrum of cellular functions, including metabolism and growth and differentiation. We sought to isolate novel members of this family by using degenerate oligonucleotide primers directed to sequences encoding the AF-2 domain of these molecules in a PCR-based approach. The AF-2 domain serves a critical function in recruiting coregulatory molecules and in transcriptional activation. We report the cloning and initial characterization of a novel gene, WDR10, which encodes a 140-kD protein that is highly expressed in pituitary and testis. This protein, WDR10p, contains an AF-2 domain as well as seven N-terminal WD repeats and is highly conserved through evolution. Chromosomal localization studies placed WDR10 at 3q21, near a locus for the Moebius syndrome, Hailey-Hailey disease, and rhodopsin, which is involved in several forms of retinitis pigmentosa. The expression pattern of WDR10 and its chromosomal location makes this novel gene a candidate gene for the hypogonadism associated with some forms of retinitis pigmentosa and the Moebius syndrome.

Two isoforms of sarco/endoplasmic reticulum calcium ATPase (SERCA) are essential in Caenorhabditis elegans

SERCA (Sarco/Endoplasmic Reticulum Calcium ATPase), a membrane bound Ca(2+)- /Mg(2+)- dependent ATPase that sequesters Ca(2+) into the SR/ER lumen, is one of the essential components for the maintenance of intracellular Ca(2+) homeostasis. Here we describe the identification and functional characterization of a C. elegans SERCA gene (ser-1). ser-1 is a single gene alternatively spliced at its carboxyl terminus to form two isoforms (SER-1A and SER-1B) and displays a high homology (70% identity, 80% similarity) with mammalian SERCAs. Green fluorescent protein (GFP) and whole-mount immunostaining analyses reveal that SER-1 expresses in neuronal cells, body-wall muscles, pharyngeal and vulval muscles, excretory cells, and vulva epithelial cells. Furthermore, SER-1::GFP expresses during embryonic stages and the expression is maintained through the adult stages. Double-stranded RNA injection (also known as RNAi) targeted to each SER-1 isoform results in severe phenotypic defects: ser-1A(RNAi) animals show embryonic lethality, whereas ser-1B(RNAi) results in L1 larval arrest phenotype. These findings suggest that both isoforms of C. elegans SERCA, like in mammals, are essential for embryonic development and post-embryonic growth and survival.

Assignment of the gene for a new hereditary nail disorder, isolated congenital nail dysplasia, to chromosome 17p13

Isolated congenital nail dysplasia is an autosomal dominant disorder recently observed in a large family from southern Germany. The disorder is characterized by longitudinal streaks, thinning, and impaired formation of the nail plates leading to increased vulnerability of the free nail margins. In most cases, all fingernails and toenails are similarly involved with some accentuation of the thumb and great toenails. Histologic changes include hypergranulosis of the nail matrix and epithelial outgrowths from the nail bed. Patients do not show any alterations of hair growth and dentition, no malfunction of sweat glands and sensory organs, and no skeletal abnormalities. Isolated congenital nail dysplasia manifests from the first year of life with variable expressivity. In order to localize chromosomally the gene underlying isolated congenital nail dysplasia, linkage to the known keratin gene cluster regions on chromosomes 12q12 and 17q21 was ruled out first. The analysis of 150 microsatellite markers on various chromosomes mapped the isolated congenital nail dysplasia gene to the 6 cM interval between markers at D17S926 and D17S1528 on chromosome 17p13. Markers at D17S849, D17S 1840, and D17S1529 co-segregated completely with the isolated congenital nail dysplasia locus. The maximum two-point LOD score was found for the marker at D17S 1840 (Zmax = 6.72 at Thetamax = 0.00). The identified region harbors no currently known genes involved in skin or nail abnormalities. Isolated congenital nail dysplasia probably represents a novel isolated defect of nail development. The localization of this gene is, therefore, the first step towards the identification of a new factor in nail formation.

Sarco(endo)plasmic reticulum calcium pumps: recent advances in our understanding of structure/function and biology (review)

This review examines the structure and function of the sarco(endo)plasmic reticulum calcium pump (SERCA1a) in the light of the recent publication of the 2.6 A resolution structure of this protein, and looks at the increasing awareness of the key role played by SERCAs in calcium signalling. The roles played by the calcium pump isoforms, SERCA1a/b, SERCA2a/b and SERCA3a/b/c in cellular function are discussed, and the modulation of SERCA activity by phospholamban, sarcolipin and other modulatory influences is examined. The recent discoveries of human SERCA mutations leading to disease states is reviewed, and the insights into SERCA function using transgenic approaches are outlined.

Abnormal intracellular ca(2+)homeostasis and disease

A whole range of cell functions are regulated by the free cytosolic Ca(2+)concentration. Activator Ca(2+)from the extracellular space enters the cell through various types of Ca(2+)channels and sometimes the Na(+)/Ca(2+)-exchanger, and is actively extruded from the cell by Ca(2+)pumps and Na(+)/Ca(2+)-exchangers. Activator Ca(2+)can also be released from internal Ca(2+)stores through inositol trisphosphate or ryanodine receptors and is taken up into these organelles by means of Ca(2+)pumps. The resulting Ca(2+)signal is highly organized in space, frequency and amplitude because the localization and the integrated free cytosolic Ca(2+)concentration over time contain specific information. Mutations or functional abnormalities in the various Ca(2+)transporters, which in vitro seem to induce trivial functional alterations, therefore, often lead to a plethora of diseases. Skeletal-muscle pathology can be caused by mutations in ryanodine receptors (malignant hyperthermia, porcine stress syndrome, central-core disease), dihydropyridine receptors (familial hypokalemic periodic paralysis, malignant hyperthermia, muscular dysgenesis) or Ca(2+)pumps (Brody disease). Ca(2+)-pump mutations in cutaneous epidermal keratinocytes and cochlear hair cells lead to, skin diseases (Darier and Hailey-Hailey) and hearing/vestibular problems respectively. Mutated Ca(2+)channels in the photoreceptor plasma membrane cause vision problems. Hemiplegic migraine, spinocerebellar ataxia type-6, one form of episodic ataxia and some forms of epilepsy can be due to mutations in plasma-membrane Ca(2+)channels, while antibodies against these channels play a pathogenic role in all patients with the Lambert-Eaton myasthenic syndrome and may be of significance in sporadic amyotrophic lateral sclerosis. Brain inositol trisphosphate receptors have been hypothesized to contribute to the pathology in opisthotonos mice, manic-depressive illness and perhaps Alzheimer's disease. Various abnormalities in Ca(2+)-handling proteins have been described in heart during aging, hypertrophy, heart failure and during treatment with immunosuppressive drugs and in diabetes mellitus. In some instances, disease-causing mutations or abnormalities provide us with new insights into the cell biology of the various Ca(2+)transporters.