Tadalafil Enhances Immune Signatures in Response to Neoadjuvant Nivolumab in Resectable Head and Neck Squamous Cell Carcinoma

PURPOSE

We hypothesize that the addition of the phosphodiesterase-5 inhibitor tadalafil to the PD-1 inhibitor nivolumab, is safe and will augment immune-mediated antitumor responses in previously untreated squamous cell carcinoma of the head and neck (HNSCC).

PATIENTS AND METHODS

We conducted a two-arm multi-institutional neoadjuvant randomized trial in any-stage resectable HNSCC (NCT03238365). Patients were stratified at randomization by human papillomavirus (HPV) status. Patients in both arms received nivolumab 240 mg intravenously on days 1 and 15 followed by surgery on day 28. Those in the combination therapy arm also received tadalafil 10 mg orally once daily for 4 weeks. Imaging, blood, and tumor were obtained pretreatment and posttreatment for correlative analysis.

RESULTS

Neoadjuvant therapy was well-tolerated with no grade 3 to 5 adverse events and no surgical delays. Twenty-five of 46 (54%) evaluable patients had a pathologic treatment response of ≥20%, including three (7%) patients with a complete pathologic response. Regardless of HPV status, tumor proliferation rate was a negative predictor of response. A strong pretreatment T-cell signature in the HPV-negative cohort was a predictor of response. Tadalafil altered the immune microenvironment, as evidenced by transcriptome data identifying enriched B- and natural killer cell gene sets in the tumor and augmented effector T cells in the periphery.

CONCLUSIONS

Preoperative nivolumab ± tadalafil is safe in HNSCC and results in more than 50% of the patients having a pathologic treatment response of at least 20% after 4 weeks of treatment. Pretreatment specimens identified HPV status-dependent signatures that predicted response to immunotherapy while posttreatment specimens showed augmentation of the immune microenvironment with the addition of tadalafil.

Pathologic and radiographic responses in a window of opportunity for durvalumab plus metformin trial for squamous cell carcinoma of the head and neck (HNSCC)

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Background: Durvalumab is a human monoclonal IgG1 antibody directed against programmed death-ligand 1 (PD-L1). PD-1/PD-L1 immune checkpoint inhibition (ICI) shows promise in HNSCC, but durable responses have been seen in only a fraction of patients. Metformin, a biguanide oral anti-hyperglycemic, has shown promise in altering immunity within the tumor microenvironment (TME) towards a stronger anti-tumor distribution of immune cells. We aimed to investigate the combined effect of metformin and durvalumab in patients with HNSCC. Methods: This was a single-center prospective phase 1, window of opportunity clinical trial in which previously untreated patients with any stage resectable HNSCC were randomized 3:1 to durvalumab + metformin (Arm A) or durvalumab alone (Arm B) during a four-week period between diagnosis and surgical resection. Six patients were included in a safety lead-in of durvalumab and metformin and an additional 32 patients were randomized. The primary endpoint was immune cell polarization. Here we report pathologic and radiographic effect. Pathologic effect was graded independently by two pathologists. Radiographic effect was evaluated using the immune-related Response Criteria (irRC). Results: Thirty-eight patients were enrolled (29 Arm A, 9 Arm B). Three patients withdrew consent prior to intervention (2 Arm A, 1 Arm B) and were excluded from analysis. AJCC 8th edition staging was as follows: Stage I (n = 21), Stage II (n = 2), Stage III (n = 3), Stage IVa (n = 6), Stage IVb (n = 3). Primary tumor sites included the oropharynx (n = 20, all p16+), oral cavity (n = 11), larynx (n = 2), maxillary sinus (n = 1), and unknown (n = 1). Pathologic effect was observed in 55% (18/33) of evaluable patients: 60% in Arm A vs 37.5% in Arm B (p = 0.418). 40% of patients with involved lymph nodes had discordance of pathologic effect at the primary site versus lymph node. Radiographic response based on irRC among 30 evaluable patients included 1 CR, 1 PR, 24 SD, and 4 PD. There was a significant correlation between pathologic effect and radiographic disease control, defined as CR, PR, and SD (p = 0.021), but no correlation when looking only at radiographic responders (p = 0.925). No patients experienced Grade 3–4 treatment or immune-related adverse events or a delay in surgery due to trial participation. All patients remained resectable. Conclusions: Our data demonstrate that the study intervention was well-tolerated in HNSCC patients. There was a trend towards an increased proportion of pathologic responders in the group receiving metformin. Additional studies targeting the TME are needed to further elucidate whether synergistic effects between metformin and durvalumab were seen in this patient cohort. Clinical trial information: NCT03618654.

Feasibility study for clinical application of caspase-3 inhibitors in Pemphigus vulgaris

The potentially severe side effects of systemic corticosteroids and immunosuppressants used in Pemphigus vulgaris (PV) call for novel therapeutic approaches. In this context, pharmacological inhibition of major pathogenic signalling effectors represents a promising alternative. However, we have also shown that overinhibition of effectors required for epidermal homeostasis can exacerbate PV pathophysiology implicating transepidermal keratinocyte fragility. A feedforward target validation therefore preferentially includes studies on knockout mouse models. We previously reported on successful amelioration of PV blisters following inhibition of non-apoptotic, low-level caspase-3. Here, we use conditional, keratinocyte-specific caspase-3-deficient mice (casp3^EKO ) to demonstrate (i) absence of keratinocyte fragility upon injection of the potent Dsg3-specific antibody AK23 and (ii) amelioration of blistering on the background of known signalling effectors. Our results provide the experimental proof of concept justifying translation of the caspase-3 inhibitor approach into PV clinical trials.

Metformin Clinical Trial in HPV+ and HPV- Head and Neck Squamous Cell Carcinoma: Impact on Cancer Cell Apoptosis and Immune Infiltrate

Background: Metformin, an oral anti-hyperglycemic drug which inhibits mitochondrial complex I and oxidative phosphorylation has been reported to correlate with improved outcomes in head and neck squamous cell carcinoma (HNSCC) and other cancers. This effect is postulated to occur through disruption of tumor-driven metabolic and immune dysregulation in the tumor microenvironment (TME). We report new findings on the impact of metformin on the tumor and immune elements of the TME from a clinical trial of metformin in HNSCC.

Methods: Human papilloma virus—(HPV–) tobacco+ mucosal HNSCC samples (n = 12) were compared to HPV+ oropharyngeal squamous cell carcinoma (OPSCC) samples (n = 17) from patients enrolled in a clinical trial. Apoptosis in tumor samples pre- and post-treatment with metformin was compared by deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Metastatic lymph nodes with extra-capsular extension (ECE) in metformin-treated patients (n = 7) were compared to archival lymph node samples with ECE (n = 11) for differences in immune markers quantified by digital image analysis using co-localization and nuclear algorithms (PD-L1, FoxP3, CD163, CD8).

Results: HPV–, tobacco + HNSCC (mean Δ 13.7/high power field) specimens had a significantly higher increase in apoptosis compared to HPV+ OPSCC specimens (mean Δ 5.7/high power field) (p < 0.001). Analysis of the stroma at the invasive front in ECE nodal specimens from both HPV—HNSCC and HPV+ OPSCC metformin treated specimens showed increased CD8+ effector T cell infiltrate (mean 22.8%) compared to archival specimens (mean 10.7%) (p = 0.006). Similarly, metformin treated specimens showed an increased FoxP3+ regulatory T cell infiltrate (mean 9%) compared to non-treated archival specimens (mean 5%) (p = 0.019).

Conclusions: This study presents novel data demonstrating that metformin differentially impacts HNSCC subtypes with greater apoptosis in HPV—HNSCC compared to HPV+ OPSCC. Moreover, we present the first in vivo human evidence that metformin may also trigger increased CD8+ Teff and FoxP3+ Tregs in the TME, suggesting an immunomodulatory effect in HNSCC. Further research is necessary to assess the effect of metformin on the TME of HNSCC.

Palmitoylation of Desmoglein 2 Is a Regulator of Assembly Dynamics and Protein Turnover

Desmosomes are prominent adhesive junctions present between many epithelial cells as well as cardiomyocytes. The mechanisms controlling desmosome assembly and remodeling in epithelial and cardiac tissue are poorly understood. We recently identified protein palmitoylation as a mechanism regulating desmosome dynamics. In this study, we have focused on the palmitoylation of the desmosomal cadherin desmoglein-2 (Dsg2) and characterized the role that palmitoylation of Dsg2 plays in its localization and stability in cultured cells. We identified two cysteine residues in the juxtamembrane (intracellular anchor) domain of Dsg2 that, when mutated, eliminate its palmitoylation. These cysteine residues are conserved in all four desmoglein family members. Although mutant Dsg2 localizes to endogenous desmosomes, there is a significant delay in its incorporation into junctions, and the mutant is also present in a cytoplasmic pool. Triton X-100 solubility assays demonstrate that mutant Dsg2 is more soluble than wild-type protein. Interestingly, trafficking of the mutant Dsg2 to the cell surface was delayed, and a pool of the non-palmitoylated Dsg2 co-localized with lysosomal markers. Taken together, these data suggest that palmitoylation of Dsg2 regulates protein transport to the plasma membrane. Modulation of the palmitoylation status of desmosomal cadherins can affect desmosome dynamics.

Palmitoylation of plakophilin is required for desmosome assembly

Desmosomes are prominent adhesive junctions found in various epithelial tissues. The cytoplasmic domains of desmosomal cadherins interact with a host of desmosomal plaque proteins, including plakophilins, plakoglobin and desmoplakin, which, in turn, recruit the intermediate filament cytoskeleton to sites of cell-cell contact. Although the individual components of the desmosome are known, mechanisms regulating the assembly of this junction are poorly understood. Protein palmitoylation is a posttranslational lipid modification that plays an important role in protein trafficking and function. Here, we demonstrate that multiple desmosomal components are palmitoylated in vivo. Pharmacologic inhibition of palmitoylation disrupts desmosome assembly at cell-cell borders. We mapped the site of plakophilin palmitoylation to a conserved cysteine residue present in the armadillo repeat domain. Mutation of this single cysteine residue prevents palmitoylation, disrupts plakophilin incorporation into the desmosomal plaque and prevents plakophilin-dependent desmosome assembly. Finally, plakophilin mutants unable to become palmitoylated act in a dominant-negative manner to disrupt proper localization of endogenous desmosome components and decrease desmosomal adhesion. Taken together, these data demonstrate that palmitoylation of desmosomal components is important for desmosome assembly and adhesion.

Reduced fibulin-2 contributes to loss of basement membrane integrity and skin blistering in mice lacking integrin α3β1 in the epidermis

Deficient epidermal adhesion is a hallmark of blistering skin disorders and chronic wounds, implicating integrins as potential therapeutic targets. Integrin α3β1, a major receptor in the epidermis for adhesion to laminin-332 (LN-332), has critical roles in basement membrane (BM) organization during skin development. In the current study we identify a role for α3β1 in promoting stability of nascent epidermal BMs through induction of fibulin-2, a matrix-associated protein that binds LN-332. We demonstrate that mice lacking α3β1 in the epidermis display ruptured BM beneath neo-epidermis of wounds, characterized by extensive blistering. This junctional blistering phenocopies defects reported in newborn α3-null mice, as well as in human patients with α3 gene mutations, indicating that the developmental role of α3β1 in BM organization is recapitulated during wound healing. Mice lacking epidermal α3β1 also have reduced fibulin-2 expression, and fibulin-2-null mice display perinatal skin blisters similar to those in α3β1-deficient mice. Interestingly, α3-null wound epidermis or keratinocytes also show impaired processing of the LN-332 γ2 chain, although this defect was independent of reduced fibulin-2 and did not appear to cause blistering. Our findings indicate a role for integrin α3β1 in BM stability through fibulin-2 induction, both in neonatal skin and in adult wounds.

Intense pulsed light photorejuvenation: a histological and immunohistochemical evaluation

BACKGROUND

The use of intense pulsed light (IPL) for facial rejuvenation had been the topic of many studies. However, few of them discussed quantitative changes in extracellular matrix proteins after IPL therapy.

OBJECTIVE

To objectively quantify the histological changes in extracellular matrix proteins after IPL treatment for facial wrinkles.

METHODS

Biopsy specimens were obtained from the periocular area of six volunteers of Fitzpatrick skin type III-IV and Glogau's class I-III wrinkles. They were subjected to three months of IPL treatment (six sessions at two-week intervals). Using histological and immunostaining analysis coupled with computerized morphometric analysis, quantitative evaluation of collagen types I, III and VII, newly synthesized collagen, total elastin and tropoelastin was performed for skin biopsies at baseline, end of treatment, and three months post-treatment.

RESULTS

Clinical assessment of volunteers did not show clinically noticeable improvement in facial wrinkles after IPL treatment. Furthermore, quantitative evaluation of extracellular matrix proteins showed no statistically significant changes (P>0.05) in response to IPL treatment

CONCLUSION

Although 50 percent of volunteers showed mild improvement in skin texture at the end of IPL treatment, none of them reported improvement in skin tightening or wrinkles. No statistically significant histological changes were observed three months post IPL treatment.

Radiofrequency facial rejuvenation: evidence-based effect

BACKGROUND

Multiple therapies involving ablative and nonablative techniques have been developed for rejuvenation of photodamaged skin. Monopolar radiofrequency (RF) is emerging as a gentler, nonablative skin-tightening device that delivers uniform heat to the dermis at a controlled depth.

OBJECTIVE

We evaluated the clinical effects and objectively quantified the histologic changes of the nonablative RF device in the treatment of photoaging.

METHODS

Six individuals of Fitzpatrick skin type III to IV and Glogau class I to II wrinkles were subjected to 3 months of treatment (6 sessions at 2-week intervals). Standard photographs and skin biopsy specimens were obtained at baseline, and at 3 and 6 months after the start of treatment. We performed quantitative evaluation of total elastin, collagen types I and III, and newly synthesized collagen using computerized histometric and immunohistochemical techniques. Blinded photographs were independently scored for wrinkle improvement.

RESULTS

RF produced noticeable clinical results, with high satisfaction and corresponding facial skin improvement. Compared with the baseline, there was a statistically significant increase in the mean of collagen types I and III, and newly synthesized collagen, while the mean of total elastin was significantly decreased, at the end of treatment and 3 months posttreatment.

LIMITATIONS

A limitation of this study is the small number of patients, yet the results show a significant improvement.

CONCLUSIONS

Although the results may not be as impressive as those obtained by ablative treatments, RF is a promising treatment option for photoaging with fewer side effects and downtime.

Electro-optical Synergy Technique: A New and Effective Nonablative Approach to Skin Aging

OBJECTIVES

Electro-optical synergy technology is one of the most recently described methods for nonablative skin rejuvenation. The aim of this study is to evaluate the effects of electro-optical synergy on connective tissue composition by histological and immunohistochemical techniques coupled with computerized morphometric analysis.

DESIGN

A prospective clinical study.

PARTICIPANTS

Six volunteers with Fitzpatrick skin types 3 to 4 and Glogau class I to II wrinkles were subjected to three months (6 sessions at 2-week intervals) of electro-optical synergy treatment.

MEASUREMENTS

Standard photographs and skin biopsies were obtained at baseline as well as three and six months after the start of treatment. The authors performed quantitative evaluation of total elastin, tropoelastin, collagen types I, III, and VII, and newly synthesized collagen.

RESULTS

Noticeable clinical and histological improvement was observed after electro-optical synergy treatment. A statistically significant increase in the means of collagen types I, III, and VII, as well as newly synthesized collagen, together with increased levels of tropoelastin, were detected, while the mean level of total elastin was significantly decreased at the end of treatment and three months post-treatment.

CONCLUSION

Electro-optical synergy is an effective treatment for contouring facial skin laxity. This modality stimulates the repair processes and reverses the clinical, as well as the histopathological, signs of aging with the advantage of being a relatively risk-free procedure with minimal patient recovery time.

Compound heterozygous desmoplakin mutations result in a phenotype with a combination of myocardial, skin, hair, and enamel abnormalities

Desmoplakin (DP) anchors the intermediate filament cytoskeleton to the desmosomal cadherins and thereby confers structural stability to tissues. In this study, we present a patient with extensive mucocutaneous blisters, epidermolytic palmoplantar keratoderma, nail dystrophy, enamel dysplasia, and sparse woolly hair. The patient died at the age of 14 years from undiagnosed cardiomyopathy. The skin showed hyperplasia and acantholysis in the mid- and lower epidermal layers, whereas the heart showed extensive fibrosis and fibrofatty replacement in both ventricles. Immunofluorescence microscopy showed a reduction in the C-terminal domain of DP in the skin and oral mucosa. Sequencing of the DP gene showed undescribed mutations in the maternal and paternal alleles. Both mutations affected exon 24 encoding the C-terminal domain. The paternal mutation, c.6310delA, leads to a premature stop codon. The maternal mutation, c.7964 C to A, results in a substitution of an aspartic acid for a conserved alanine residue at amino acid 2655 (A2655D). Structural modeling indicated that this mutation changes the electrostatic potential of the mutated region of DP, possibly altering functions that depend on intermolecular interactions. To conclude, we describe a combination of DP mutation phenotypes affecting the skin, heart, hair, and teeth. This patient case emphasizes the importance of heart examination of patients with desmosomal genodermatoses.

Extracellular matrix in cutaneous ageing: the effects of 0.1% copper-zinc malonate-containing cream on elastin biosynthesis

Cutaneous ageing, as visualized at the exposed areas of skin, reflects dramatic alterations in the structure and function of the extracellular matrix of connective tissues. Among them, the elastic fibre network, which is responsible for the physiological elasticity and resilience of normal skin, undergoes degradative changes leading to loss of functional elastic fibres. A potential strategy to counteract these degenerative changes entails topical application of a compound that may lead to regeneration of the elastic fibre network. In this study, we have evaluated the effects of a bi-metal, 0.1% copper-zinc malonate-containing cream that has been shown to efface wrinkles in clinical trials. An effect on elastin biosynthesis and elastic tissue accumulation in skin biopsies was observed in 21 female patients with photoaged facial skin, as measured at baseline and at 6 weeks of treatment. Histopathological evaluation revealed evidence of elastic fibre regeneration, including those extending perpendicularly towards the dermo-epidermal junction within the papillary dermis. Elastin biosynthesis, measured by semi-quantitative immunofluorescence with an antibody recognizing only the newly synthesized, uncrosslinked tropoelastin molecules, suggested statistically significant enhancement of elastin biosynthesis by the bi-metal compound when applied twice daily. Accumulation of elastic fibres was confirmed by assay of desmosine, an elastin-specific crosslink compound. These results suggest that the bi-metal, 0.1% copper-zinc malonate-containing cream has the propensity to increase elastin synthesis in human skin in vivo, and that regeneration of elastic fibres may contribute to wrinkle effacement in female patients with photoaged facial skin.

Decreased Plakophilin-1 Expression Promotes Increased Motility in Head and Neck Squamous Cell Carcinoma Cells

Desmosomes are prominent cell-cell adhesive junctions found in a variety of epithelial tissues, including the oral epithelium. The transmembrane core of the desmosome is composed of the desmosomal cadherins that interact extracellularly to mediate cell-cell adhesion. The cytoplasmic domain of desmosomal cadherins interact with plaque proteins that in turn interact with the keratin intermediate filament cytoskeleton. Plakophilin 1 is a major desmosomal plaque component that functions to recruit intermediate filaments to sites of cell-cell contact via interactions with desmoplakin. Decreased assembly of desmosomes has been reported in several epithelial cancers. We examined plakophilin-1 expression in an esophageal squamous cell carcinoma tissue microarray and found that plakophilin-1 expression inversely correlates with tumor grade. In addition, we sought to investigate the effect of plakophilin-1 expression on desmosome assembly and cell motility in oral squamous cell carcinoma cell lines. Cell lines expressing altered levels of plakophilin-1 were generated and the ability of these cells to recruit desmoplakin to sites of cell-cell contact was examined. Our results show that decreased expression of plakophilin-1 results in decreased desmosome assembly and increased cell motility and invasion. These data lead us to propose that loss of plakophilin-1 expression during head and neck squamous cell carcinoma (HNSCC) progression may contribute to an invasive phenotype.

Deregulation of keratinocyte differentiation and activation: a hallmark of venous ulcers

Epidermal morphology of chronic wounds differs from that of normal epidermis. Biopsies of non-healing edges obtained from patients with venous ulcers show thick and hyperproliferative epidermis with mitosis present in suprabasal layers. This epidermis is also hyper-keratotic and parakeratotic. This suggests incomplete activation and differentiation of keratinocytes. To identify molecular changes that lead to pathogenic alterations in keratinocyte activation and differentiation pathways we isolated mRNA from non-healing edges deriving from venous ulcers patients and determined transcriptional profiles using Affymetrix chips. Obtained transcriptional profiles were compared to those from healthy, unwounded skin. As previously indicated by histology, we found deregulation of differentiation and activation markers. We also found differential regulation of signalling molecules that regulate these two processes. Early differentiation markers, keratins K1/K10 and a subset of small proline-rich proteins, along with the late differentiation marker filaggrin were suppressed, whereas late differentiation markers involucrin, transgultaminase 1 and another subset of small proline-rich proteins were induced in ulcers when compared to healthy skin. Surprisingly, desomosomal and tight junction components were also deregulated. Keratinocyte activation markers keratins K6/K16/K17 were induced. We conclude that keratinocytes at the non-healing edges of venous ulcers do not execute either activation or differentiation pathway, resulting in thick callus-like formation at the edge of a venous ulcers.

Suprabasal Dsg2 expression in transgenic mouse skin confers a hyperproliferative and apoptosis-resistant phenotype to keratinocytes

Desmoglein 2 (Dsg2), a component of the desmosomal cell-cell adhesion structure, has been linked to invasion and metastasis in squamous cell carcinomas. However, it is unknown whether – and if so how – Dsg2 contributes to the malignant phenotype of keratinocytes. In this study, we addressed the consequences of Dsg2 overexpression under control of the involucrin promoter (Inv-Dsg2) in the epidermis of transgenic mice. These mice exhibited epidermal hyperkeratosis with slightly disrupted early and late differentiation markers, but intact epidermal barrier function. However, Inv-Dsg2 transgene expression was associated with extensive epidermal hyperplasia and increased keratinocyte proliferation in basal and suprabasal epidermal strata. Cultured Inv-Dsg2 keratinocytes showed enhanced cell survival in the anchorage-independent state that was critically dependent on EGF receptor activation and NF-κB activity. Consistent with the hyperproliferative and apoptosis-resistant phenotype of Inv-Dsg2 transgenic keratinocytes, we observed enhanced activation of multiple growth and survival pathways, including PI 3-kinase/AKT, MEK-MAPK, STAT3 and NF-κB, in the transgenic skin in situ. Finally, Inv-Dsg2 transgenic mice developed intraepidermal skin lesions resembling precancerous papillomas and were more susceptible to chemically induced carcinogenesis. In summary, overexpression of Dsg2 in epidermal keratinocytes deregulates multiple signaling pathways associated with increased growth rate, anchorage-independent cell survival, and the development of skin tumors in vivo.

Desmoglein 4 is expressed in highly differentiated keratinocytes and trichocytes in human epidermis and hair follicle

Desmosomes are critical for the tissue integrity of stratified epithelia and their appendages. Desmogleins (DSGs) and desmocollins (DSCs) are transmembrane desmosomal cadherins that interact extracellularly to link neighboring epithelial cells. We recently identified a new member of the DSG family, designated desmoglein 4, whose mutations cause hypotrichosis in human, mouse and rat. In this study, we analyzed in detail the expression domains of human desmoglein 4 protein (DSG4) in human skin relative to differentiation markers and other DSGs. Our results show that DSG4 protein is expressed in the more highly differentiated layers of the epidermis. This expression pattern in vivo is recapitulated in highly differentiated HaCaT human keratinocytes and normal human keratinocytes in vitro. In the human hair follicle, DSG4 is expressed specifically in the hair shaft cortex, the lower hair cuticle, and the upper inner root sheath (IRS) cuticle. Using a green fluorescent protein-tagged version of mouse or rat desmoglein 4 protein (Dsg4) and immuno-electron microscopy, we demonstrate that Dsg4 localizes to desmosomes both in vitro and in vivo. The highly specific expression pattern of DSG4 in the human hair follicle, combined with the phenotype of rodent models and human patients with desmoglein 4 mutations, underscores the importance of this adhesion molecule in the integrity of the hair shaft.

Delineation of diversified desmoglein distribution in stratified squamous epithelia: implications in diseases

Desmogleins play critical roles in cell adhesion and skin blistering diseases, as they are the target antigens of autoimmune antibodies and bacterial toxins. We recently cloned several novel members of the desmoglein gene family, bringing the number of desmogleins to four in the rat and human genomes and six in the mouse. Here, we have produced a monoclonal antibody to a cytoplasmic epitope of Dsg4, assessed its specificity and compared it to several existing Dsg1-3 antibodies. We also demonstrated cross-reactivity of commercially available and often used Dsg1 antibodies. Using these tools, we delineated the unique expression patterns of each desmoglein isoform in various human and mouse stratified squamous epithelia, including skin, hair, palm, and oral mucosa. Interestingly, in the epidermis, the expression of each desmoglein correlates with their gene arrangement in the cadherin locus. In human, Dsg4 was detected primarily in the granular and cornified cell layers of the epidermis, while present throughout all differentiated layers of the oral mucosa and palm, and in the matrix cells of anagen hair bulb. Similar pattern of expression for Dsg4 was observed in mouse, with the exception that it was expressed at significantly lower levels in the mouse epidermis. These results demonstrate the complexity of desmoglein gene expression and provide additional insights into the correlation between tissue expression patterns and disease phenotypes.

Differential structural properties and expression patterns suggest functional significance for multiple mouse desmoglein 1 isoforms

The four isoforms of desmosomal cadherin desmogleins (Dsg1-4) are expressed in epithelial tissues in a differentiation-specific manner. Extensive sequencing of the human genome has revealed only one copy of the Dsg1 gene. However, we recently cloned two novel additional mouse Dsg1 genes, Dsg1-beta and -gamma, which flank the original Dsg1-alpha on chromosome 18. Sequence conservation between the Dsg1 isoforms diverged significantly at exon 11, particularly in the region that encodes for the extracellular anchoring (EA) domains. Computational analysis revealed very low hydrophilic potential of the Dsg1-gamma EA compared with the corresponding sequences of Dsg1-alpha and -beta, suggesting that the Dsg1-gamma EA domain may have a stronger affinity to the cell membrane. We generated antibodies using synthetic peptides or recombinant proteins localized within the EA domains. These antibodies were tested for their specificity and were then used to demonstrate expression of Dsg1 isoforms in various tissues. In the epidermis, all Dsg1 isoforms were differentially expressed in the differentiating cell layers. In the hair follicle, all Dsg1 isoforms were present throughout the entire process of its development and cycling but the expression of Dsg1 isoforms is subject to significant hair cycle-dependent changes. Dsg1-beta and -gamma, but not Dsg1-alpha, were detected in the sebaceous gland epithelium and the stratified epithelium of the stomach. Finally, Dsg1-alpha and Dsg1-beta, but not Dsg1-gamma, are proteolytically cleaved by exfoliative toxin A. These results suggest that the developmental complexity of mouse tissues, including skin and hair, may play a significant role in the evolutionary driving force to maintain multiple Dsg1 genes in mouse.

Upstream determinants of estrogen receptor-alpha regulation of metastatic tumor antigen 3 pathway

Although recent studies have shown a role of estrogen receptor-alpha (ER) in the regulation of epithelial-to-mesenchymal transition via MTA3, the role of upstream determinants of ER regulation of MTA3 and the underlying molecular mechanism remains unknown. Here we show that MTA3 gene regulation by ER is influenced by dynamic changes in levels of nuclear coregulators. MTA3 promoter has a functional ER element half-site with which MTA1 and HDACs interact under basal conditions. Upon estrogen stimulation, these corepressors are derecruited with concomitant recruitment of ER, leading to increased MTA3 transcription and expression. Genetic inactivation of MTA1 pathway promotes the ability of ER to up-regulate MTA3 expression, whereas knockdown of ER enhances MTA1 association with MTA3 gene. Modulation of ER functions, by corepressors (i.e. MTA1 and MTA1s) or coactivators (i.e. AIB1 and PELP1/MNAR), alters ER recruitment to MTA3 chromatin, MTA3 transcription, and expression of downstream epithelial-to-mesenchymal transition components. These studies provide novel insights into the transregulation of the MTA3 gene and reveal novel roles of upstream determinants in modifying the outcome of MTA3 axis and cell differentiation.

Desmoglein 4 in hair follicle differentiation and epidermal adhesion: evidence from inherited hypotrichosis and acquired pemphigus vulgaris

Cell adhesion and communication are interdependent aspects of cell behavior that are critical for morphogenesis and tissue architecture. In the skin, epidermal adhesion is mediated in part by specialized cell-cell junctions known as desmosomes, which are characterized by the presence of desmosomal cadherins, known as desmogleins and desmocollins. We identified a cadherin family member, desmoglein 4, which is expressed in the suprabasal epidermis and hair follicle. The essential role of desmoglein 4 in skin was established by identifying mutations in families with inherited hypotrichosis, as well as in the lanceolate hair mouse. We also show that DSG4 is an autoantigen in pemphigus vulgaris. Characterization of the phenotype of naturally occurring mutant mice revealed disruption of desmosomal adhesion and perturbations in keratinocyte behavior. We provide evidence that desmoglein 4 is a key mediator of keratinocyte cell adhesion in the hair follicle, where it coordinates the transition from proliferation to differentiation.

Novel member of the mouse desmoglein gene family: Dsg1-beta

Desmosomes are major intercellular adhesion junctions that provide stable cell-cell contacts and mechanical strength to epithelial tissues by anchoring cytokeratin intermediate filaments of adjacent cells. Desmogleins (Dsg) are transmembrane core components of the desmosomes, and belong to the cadherin supergene family of calcium-dependent adhesion molecules. Currently, there are three known isoforms of Dsgs (Dsg1, Dsg2, and Dsg3), encoded by distinct genes that are differentially expressed to determine their tissue specificity and differentiation state of epithelial cells. In this study, we cloned a novel mouse desmoglein gene sharing high homology to both mouse and human Dsg1. We propose to designate the previously published mouse Dsg1 gene as Dsg1-alpha and the new gene as Dsg1-beta. Analysis of intron/exon organization of the Dsg1-alpha and Dsg1-beta genes revealed significant conservation. The full-length mouse Dsg1-beta cDNA contains an open reading frame of 3180 bp encoding a precursor protein of 1060 amino acids. Dsg1-beta protein shares 94% and 76% identity with mouse Dsg1-alpha and human DSG1, respectively. RT-PCR using a multitissue cDNA panel demonstrated that while Dsg1-alpha mRNA was expressed in 15- to 17-day-old embryos and adult spleen and testis, Dsg1-beta mRNA was detected in 17-day-old embryos only. To assess subcellular localization, a FLAG-tagged expression construct of Dsg1-beta was transiently expressed in epithelial HaCaT cells. Dsg1-beta-FLAG was found at the cell-cell border and was recognized by the anti-Dsg1/Dsg2 antibody DG3.10. In summary, we have cloned and characterized a novel member of the mouse desmoglein gene family, Dsg1-beta.

Loss of cell adhesion in Dsg3bal-Pas mice with homozygous deletion mutation (2079del14) in the desmoglein 3 gene

Pemphigus encompasses a group of autoimmune blistering diseases with circulating pathogenic autoantibodies recognizing several proteins, including the desmosomal cadherin, desmoglein 3. Targeted disruption of the Dsg3 gene by homologous recombination (Dsg3tm1stan) in mouse results in fragility of the skin and oral mucous membranes, analogous to the human disease. In addition, the Dsg3tm1stan mice develop phenotypic runting and hair loss, identical to that of the mouse mutant, Dsg3bal-2J. The Dsg3bal-2J mice are homozygous for a 1 bp insertion (2275insT) in the Dsg3 gene resulting in a nonfunctional Dsg3 mRNA. In this study, we characterized an allelic mutation, Dsg3bal-Pas, with clinical features similar to those in Dsg3bal-2J. We have identified a 14 bp deletion in exon 13 of the Dsg3 gene resulting in a frameshift and premature termination codon 7 bp downstream from the site of the deletion and causing a truncation of the desmoglein 3 polypeptide by 199 amino acids, eliminating virtually all of the intracellular domain. We demonstrate that, although a Dsg3 mRNA transcript was detectable in Dsg3bal-Pas skin, the corresponding protein for desmoglein 3 was completely absent in the oral mucosal epithelium of homozygous Dsg3bal-Pas compared with that of +/Dsg3bal-Pas mice. No significant changes in the expression of desmogleins 1 and 2 were detected. To elucidate a potential mechanism causing loss of cell adhesion in the Dsg3bal-Pas mice, we generated a myc-tagged truncated Dsg3bal-Pas desmoglein 3 protein and expressed it in keratinocytes. The myc-tagged truncated Dsg3bal-Pas desmoglein 3 protein was found predominantly in the cytoplasm possibly due to increased proteolytic degradation. Cell surface staining was also detected but was jagged, not linear along the cell-cell border like that observed for the full-length desmoglein 3. The expression of the myc-tagged truncated Dsg3bal-Pas desmoglein 3 protein resulted in a reduction in staining of other desmosomal proteins, including desmoglein 1 and 2, plakophilin 2, and plakoglobin. In addition, the cells expressing myc-tagged truncated Dsg3bal-Pas desmoglein 3 protein underwent dramatic changes in cell morphology and exhibited striking extensive filopodia. Collectively, these data showed that the perturbation of desmoglein 3 found in the Dsg3bal-Pas mice resulted in disadhesion of keratinocytes manifested with blistering phenotype.

Interspecies conservation and differential expression of mouse desmoglein gene family

Epithelial cell adhesion is mediated by intercellular junctions, called desmosomes. Desmogleins (Dsg; Dsg1, Dsg2 and Dsg3) are calcium-dependent transmembrane adhesion components of the desmosomes. While Dsg1 and Dsg3 are mainly restricted to stratified squamous epithelia, Dsg2 is expressed in essentially all desmosome-containing epithelia. In the epidermis, Dsg2 and Dsg3 are expressed in the basal keratinocytes while Dsg1 is expressed throughout the upper differentiating cell layers. To date, in mouse, only Dsg3 has been characterized by molecular cloning. In this study, we have cloned and characterized the mouse Dsg1 and Dsg2 genes. The full-length mouse Dsg1 cDNA (5.5 kb) contains an open reading frame (ORF) of 3171 bp encoding a precursor protein of 1057 amino acids. The Dsg2 cDNA (6.3 kb) has an ORF of 3366 bp coding for a precursor protein of 1122 amino acids. Mouse Dsg2 protein shares 76% identity with human DSG2 but only 26% and 33% identity with mouse Dsg1 and Dsg3, respectively. Analysis of intron/exon organization of the desmoglein genes revealed significant conservation. However, the mRNA expression patterns of these desmogleins during mouse embryonic development and in various adult tissues are variable. While Dsg2 and Dsg3 are expressed in all developmental stages, Dsg1 expression is delayed until day 15 of mouse embryos. In adult mouse tissues, Dsg2 is widely expressed while the expression of Dsg1 and Dsg3 is restricted to select tissues. In summary, while desmogleins share high homology at both the gene and protein level, their expression is spatially and temporally regulated, potentially contributing to their significant role in cell-cell adhesion during development.

Metastasis-associated protein (MTA)1 enhances migration, invasion, and anchorage-independent survival of immortalized human keratinocytes

The human metastasis-associated gene (MTA1), a member of the nucleosome remodeling complex with histone deacetylase activity, is frequently overexpressed in biologically aggressive epithelial neoplasms. Here, we extend this observation to squamous carcinoma cells, which express high levels of MTA1 relative to normal or immortalized keratinocytes. To address functional aspects of MTA1 expression, we established variants of human immortalized keratinocytes (HaCaT cells) by expressing MTA1 cDNA in both the sense and antisense orientations. We demonstrate that (1) forced MTA1 expression enhances migration and invasion of immortalized keratinocytes; (2) MTA1 expression is necessary but not sufficient for cell survival in the anchorage independent state; (3) MTA1 contributes to expression of the anti-apoptotic Bcl-2 family member Bcl-x(L); (4) MTA1 expression in immortalized keratinocytes depends, in part, on activation of the epidermal growth factor receptor (EGFR). These results establish that, in keratinocytes, MTA1 expression contributes to several aspects of the metastatic phenotype including survival in the anchorage independent state, migration, and invasion.

Differential expression and subcellular distribution of the mouse metastasis-associated proteins Mta1 and Mta3

The human metastasis-associated gene (MTA1) is overexpressed in cell lines and tissues representing metastatic tumors. Here we report cloning of the mouse Mta1 as well as a novel structurally related mouse gene, Mta3. The mouse Mta1 protein shares 94 and 59% homology to the human MTA1 and mouse Mta3 proteins, respectively. Northern blotting analysis using an Mta1 cDNA probe revealed a prevalent 3 kb hybridization signal in all mouse tissues except the skeletal muscle while a smaller approximately 1.0 kb mRNA product was also detected in the heart. Mta3 transcripts (approximately 2 kb) were detected in most tissues with an additional approximately 6.2 kb signal detected in the brain. In vitro transcription/translation of the full-length Mta1 and Mta3 cDNAs generated products of the expected molecular masses, i.e. 80 and 60 kDa, respectively. To assess subcellular localization, green fluorescence protein (GFP)-tagged expression constructs of Mta1 and Mta3 and various deletion constructs of GFP-Mta1 were transiently expressed in Balb/MK keratinocytes. GFP-Mta1 was found exclusively in the nucleus while GFP-Mta3 was present in both the nucleus and cytoplasm. Compared to Mta3, the carboxy terminal end of Mta1 contains an additional nuclear localization signal (NLS) and a proline-rich Src homology 3 (SH3) ligand. The results of transient expression experiments of various Mta1 fragments containing these domains in different combinations indicated that nuclear localization of Mta1 depended on the presence of at least one NLS and one SH3 binding site. These SH3 ligands appeared to be functional as they facilitated interaction with the adaptor protein, Grb2, and the Src-family tyrosine kinase, Fyn.

Postnatal lethality of P-cadherin/desmoglein 3 double knockout mice: demonstration of a cooperative effect of these cell adhesion molecules in tissue homeostasis of stratified squamous epithelia

To investigate the cooperativity of different cell adhesion molecules in maintaining the structural integrity of the epidermis, we have generated mice deficient for both a classical cadherin, P-cadherin, and a desmosomal cadherin, desmoglein 3. In epithelial cells, P-cadherin is localized to the adherens junction, whereas desmoglein 3 is found in desmosomes. Previous studies have shown that these two junctional complexes are important for keratinocyte cell-cell adhesion. Both P-cadherin and desmoglein 3 expression are restricted to the basal and most immediate suprabasal cells of the epidermis, whereas both proteins are found throughout the oral mucosal epithelium. Although P-cadherin mutant mice have no apparent defect in epithelial cell adhesion, the desmoglein 3 mutant phenotype resembles that of patients with the autoimmune disease pemphigus vulgaris, in that the mice develop spontaneous mucous membrane blisters and trauma-induced skin blisters. The oral lesions in DSG3-/- mice reduce their food intake, resulting in a runted phenotype; however, most animals recover and live past weaning age. In contrast, animals mutant for both P-cadherin and desmoglein 3 die before weaning. The majority of the double mutant animals die around 1 wk after birth, apparently due to malnutrition. These studies suggest that loss of P-cadherin leads to a more severe desmoglein 3 mutant phenotype in the double knockout mice. This is the first in vivo evidence of possible synergism between a classical and desmosomal cadherin.

Pemphigus vulgaris and pemphigus foliaceus antibodies are pathogenic in plasminogen activator knockout mice

Previous studies have suggested that urokinase plasminogen activator is required for blister formation in pemphigus vulgaris and pemphigus foliaceus. Other studies, however, have shown that downregulation of plasminogen activator does not inhibit blisters induced by pemphigus immunoglobulin G. To eliminate the possibility that small amounts of urokinase plasminogen activator might be sufficient for blister formation, we passively transferred pemphigus immunoglobulin G to urokinase plasminogen activator knockout neonatal mice. Pemphigus foliaceus and pemphigus vulgaris immunoglobulin G caused gross blisters and acantholysis in the superficial and suprabasal epidermis, respectively, to the same degree in knockout and control mice, demonstrating that urokinase plasminogen activator is not absolutely required for antibody-induced blisters. Some studies have shown elevated tissue-type plasminogen activator in pemphigus lesions. Tissue-type plasminogen activator, however, is not necessary for blister formation, because pemphigus foliaceus and pemphigus vulgaris immunoglobulin G caused blisters to the same degree in tissue-type plasminogen activator knockout and control mice. To rule out that one plasminogen activator might compensate for the other in the knockout mice, we bred urokinase plasminogen activator, tissue-type plasminogen activator double knockouts. After passive transfer of pemphigus foliaceus and pemphigus vulgaris immunoglobulin G these mice blistered to the same degree as the single knockout and control mice, and histology indicated blisters at the expected level of the epidermis. These data definitively demonstrate that plasminogen activator is not necessary for pemphigus immunoglobulin G to induce acantholysis in the neonatal mouse model of pemphigus.

Explanations for the clinical and microscopic localization of lesions in pemphigus foliaceus and vulgaris

Patients with pemphigus foliaceus (PF) have blisters on skin, but not mucous membranes, whereas patients with pemphigus vulgaris (PV) develop blisters on mucous membranes and/or skin. PF and PV blisters are due to loss of keratinocyte cell-cell adhesion in the superficial and deep epidermis, respectively. PF autoantibodies are directed against desmoglein (Dsg) 1; PV autoantibodies bind Dsg3 or both Dsg3 and Dsg1. In this study, we test the hypothesis that coexpression of Dsg1 and Dsg3 in keratinocytes protects against pathology due to antibody-induced dysfunction of either one alone. Using passive transfer of pemphigus IgG to normal and DSG3(null) neonatal mice, we show that in the areas of epidermis and mucous membrane that coexpress Dsg1 and Dsg3, antibodies against either desmoglein alone do not cause spontaneous blisters, but antibodies against both do. In areas (such as superficial epidermis of normal mice) where Dsg1 without Dsg3 is expressed, anti-Dsg1 antibodies alone can cause blisters. Thus, the anti-desmoglein antibody profiles in pemphigus sera and the normal tissue distributions of Dsg1 and Dsg3 determine the sites of blister formation. These studies suggest that pemphigus autoantibodies inhibit the adhesive function of desmoglein proteins, and demonstrate that either Dsg1 or Dsg3 alone is sufficient to maintain keratinocyte adhesion.

Time course of the initial [Ca2+]i response to extracellular ATP in smooth muscle depends on [Ca2+]e and ATP concentration

In response to extracellular application of 50 microM ATP, all individual porcine aortic smooth muscle cells respond with rapid rises from basal [Ca2+]i to peak [Ca2+]i within 5 s. The time from stimulus to the peak of the [Ca2+]i response increases with decreasing concentration of ATP. At ATP concentrations of 0.5 microM and below, the time to the [Ca2+]i peak varies more significantly from cell to cell than at higher concentrations, and each cell shows complicated initiation and decay kinetics. For any individual cell, the lag phase before a response decreases with increasing concentration of ATP. An increase in lag time with decreasing ATP concentration is also observed in the absence of extracellular Ca2+, but the lag phase is more pronounced, especially at concentrations of ATP below 0.5 microM. Whole-cell patch-clamp electrophysiology shows that in porcine aortic smooth muscle cells, ATP stimulates an inward current carried mainly by Cl- ion efflux with a time course similar to the [Ca2+]i changes and no detectable current from an ATP-gated cation channel. A simple signal cascade initiation kinetics model, starting with nucleotide receptor activation leading to IP3-mediated Ca2+ release from IP3-sensitive internal stores, fits the data and suggests that the kinetics of the Ca2+ response are dominated by upstream signal cascade components.

Desmoglein 3 anchors telogen hair in the follicle

Little is known about the function of desmosomes in the normal structure and function of hair. Therefore, it was surprising that mice without desmoglein 3 (the autoantigen in pemphigus vulgaris) not only developed mucous membrane and skin lesions like pemphigus patients, but also developed hair loss. Analysis of this phenotype indicated that hair was normal through the first growth phase (‘follicular neogenesis’). Around day 20, however, when the hair follicles entered the resting phase of the hair growth cycle (telogen), mice with a targeted disruption of the desmoglein 3 gene (DSG3-/-) lost hair in a wave-like pattern from the head to the tail. Hair then regrew and was lost again in the same pattern with the next synchronous hair cycle. In adults, hair was lost in patches. Gentle hair pulls with adhesive tape showed that anagen (growing) hairs were firmly anchored in DSG3-/- mice, but telogen hairs came out in clumps compared to that of DSG3+/− and +/+ littermates in which telogen hairs were firmly anchored. Histology of bald skin areas in DSG3-/- mice showed cystic telogen hair follicles without hair shafts. Histology of hair follicles in early telogen, just before clinical hair loss occurred, showed loss of cell adhesion (acantholysis) between the cells surrounding the telogen club and the basal layer of the outer root sheath epithelium. Electron microscopy revealed ‘half-desmosomes’ at the plasma membranes of acantholytic cells. Similar acantholytic histology and ultrastructural findings have been previously reported in skin and mucous membrane lesions of DSG3-/- mice and pemphigus vulgaris patients. Immunoperoxidase staining with an antibody raised against mouse desmoglein 3 showed intense staining on the cell surface of keratinocytes surrounding the telogen hair club in normal mice. Similar staining was seen in human telogen hair with an anti-human desmoglein 3 antibody. Finally, a scalp biopsy from a pemphigus vulgaris patient showed empty telogen hair follicles. These data demonstrate that desmoglein 3 is not only critical for cell adhesion in the deep stratified squamous epithelium, but also for anchoring the telogen hair to the outer root sheath of the follicle and underscore the importance of desmosomes in maintaining the normal structure and function of hair.

Translocation of the zinc finger protein basonuclin from the mouse germ cell nucleus to the midpiece of the spermatozoon during spermiogenesis

Basonuclin was first described as a human keratinocyte zinc finger protein present in the nuclei of proliferative basal keratinocytes in the epidermis. It disappears from keratinocytes that have lost their proliferative ability and have entered terminal differentiation. We now report that basonuclin is present also in the germ cells of the mouse testis and ovary. Immunocytochemical staining detected basonuclin in the nuclei of spermatogonia and spermatocytes at various developmental stages. During spermiogenesis, it relocated from the nucleus to the midpiece of the flagellum of the spermatozoa. In the ovary, basonuclin was found mainly in the nuclei of developing oocytes. The dual presence of basonuclin in differentiated spermatozoa and oocytes suggests that it may play a role in their differentiation and the early development of an embryo.

The members of the plakin family of proteins recognized by paraneoplastic pemphigus antibodies include periplakin

Sera of patients with paraneoplastic pemphigus (PNP) characteristically immunoprecipitate five proteins, observations confirmed with the sera examined in this study. The proteins characterized thus far as autoantigens in PNP all belong to the plakin family of proteins and include desmoplakin, the 230 kDa bullous pemphigoid antigen, and envoplakin. The pattern of bands precipitated from metabolically labeled human keratinocyte extracts by each PNP serum was different, suggesting varying titers of antibodies against unique epitopes in various plakin family members. To further characterize this PNP antibody response, we produced fusion proteins of the homologous tail region of five plakin family members, including the recently cloned periplakin. Immunoblotting of equal amounts of each plakin tail-glutathione S-transferase fusion protein with PNP sera revealed a strong reaction with the envoplakin tail domain. Each sera also recognized periplakin, and certain sera recognized desmoplakin and plectin, and, weakly, bullous pemphigoid antigen 1. PNP sera were affinity purified with periplakin and envoplakin tail fusion proteins. Immunoprecipitation and immunoblotting with these affinity purified antibodies revealed shared as well as unique epitopes in the tail domains of these plakins. This study indicates that a homologous region in the carboxy-terminus of plakins, including the newly characterized periplakin, serves as an antigenic site in PNP.

Targeted disruption of the pemphigus vulgaris antigen (desmoglein 3) gene in mice causes loss of keratinocyte cell adhesion with a phenotype similar to pemphigus vulgaris

In patients with pemphigus vulgaris (PV), autoantibodies against desmoglein 3 (Dsg3) cause loss of cell-cell adhesion of keratinocytes in the basal and immediate suprabasal layers of stratified squamous epithelia. The pathology, at least partially, may depend on protease release from keratinocytes, but might also result from antibodies interfering with an adhesion function of Dsg3. However, a direct role of desmogleins in cell adhesion has not been shown. To test whether Dsg3 mediates adhesion, we genetically engineered mice with a targeted disruption of the DSG3 gene. DSG3 -/- mice had no DSG3 mRNA by RNase protection assay and no Dsg3 protein by immunofluorescence (IF) and immunoblots. These mice were normal at birth, but by 8-10 d weighed less than DSG3 +/- or +/+ littermates, and at around day 18 were grossly runted. We speculated that oral lesions (typical in PV patients) might be inhibiting food intake, causing this runting. Indeed, oropharyngeal biopsies showed erosions with histology typical of PV, including suprabasilar acantholysis and "tombstoning" of basal cells. EM showed separation of desmosomes. Traumatized skin also had crusting and suprabasilar acantholysis. Runted mice showed hair loss at weaning. The runting and hair loss phenotype of DSG3 -/- mice is identical to that of a previously reported mouse mutant, balding (bal). Breeding indicated that bal is coallelic with the targeted mutation. We also showed that bal mice lack Dsg3 by IF, have typical PV oral lesions, and have a DSG3 gene mutation. These results demonstrate the critical importance of Dsg3 for adhesion in deep stratified squamous epithelia and suggest that pemphigus autoantibodies might interfere directly with such a function.

Independent modes of propagation of calcium waves in smooth muscle cells

The purinergic agonist adenosine triphosphate (ATP) stimulates an initial transient followed by subsequent oscillations in cytosolic calcium ion concentration ([Ca2+]i) in individual porcine aortic smooth muscle cells. Using microinjection of fura-2 covalently coupled to dextran, we have analyzed in detail the spatial and temporal features of the oscillations. We have observed both cytoplasmic calcium waves and gradients within single cells. Single cells can contain multiple loci of initiation of oscillations. Independent oscillations in a single cell can have independent frequencies and these oscillations can propagate without interference across the same region of the cell, suggesting that they arise either from separately regulated stores of Ca2+ or a single Ca2+ store operated by two separate release mechanisms. The shape of the wave front and the manner of the waye's decay can vary from one oscillation to the next. Ca2+ signaling in individual arterial smooth muscle cells thus displays complex spatial and temporal organization.

Independent pathways regulate the cytosolic [Ca2+] initial transient and subsequent oscillations in individual cultured arterial smooth muscle cells responding to extracellular ATP

Stimulation with extracellular ATP causes a rapid initial transient rise followed by asynchronous periodic oscillations in cytosolic calcium ion activity ([Ca2+]i) in individual aortic smooth muscle cells in either HEPES-buffered or HCO3(-)-buffered saline. The dose at which one-half of the cells display an initial rise in cytosolic calcium is 0.11 microM ATP in the presence of external Ca2+ and 0.88 microM ATP in the absence of external Ca2+; the corresponding value for oscillations in the presence of external Ca2+ is 2.6 microM ATP. While the initial transient displays rapid desensitization, the oscillations persist for greater than 30 min in the continuous presence of ATP. The presence of the agonist ATP is also absolutely required for the maintenance of the oscillations, presumably to provide continuous activation of P2 purinoceptors. The average frequency of oscillation is approximately 0.9 min-1. The frequency depends only slightly on the concentration of ATP, and oscillations do not collapse into a prolonged elevated [Ca2+]i at high concentrations of ATP. Both Ca2+ influx and release from internal stores participate in the initial transient. Oscillations are not produced in the absence of external Ca2+ but are initiated upon the addition of external Ca2+ in the continued presence of ATP. Oscillations in progress are abolished by the removal of extracellular Ca2+ with one additional peak occurring after the Ca2+ removal. These data suggest that extracellular Ca2+ influx is required for the maintenance of the posttransient oscillations, presumably to provide the Ca2+ necessary for refilling intracellular Ca2+ pools that are the source of the oscillating [Ca2+]i. The Ca2+ influx is not regulated by voltage-gated Ca2+ channels. The data in this report are consistent with the view that the initial transient has contributions from two receptor-mediated pathways, and the oscillations are controlled either by a mechanism separate from the ones that control the initial transient or by steps whose control diverges before the point of desensitization.

The impenetrability of 5-(N-hexadecanoyl)aminofluoroscein through endothelial cell monolayers is dependent upon its solution properties, not the presence of tight junctions

The solution properties of two fluorescent lipophilic analogues were examined in conjunction with their ability to penetrate the tight junctions of bovine aortic endothelial cell monolayers. 5-(N-dodecanoyl)aminofluoroscein was shown to label both the apical and basolateral plasma membrane domains of confluent monolayers at 4 degrees C and pH 7.3, but 5-(N-hexadecanoyl)aminofluoroscein was shown to label only the apical membrane domain. When used under more soluble conditions at 20 degrees C and pH 8.5, both probes labeled apical and basolateral plasma membrane domains more equally. This indicates that solubility conditions, and not tight junctions, dictate the penetration of 5-(N-hexadecanoyl)aminofluoroscein from the apical to the basolateral plasma membrane domain.

Keratinocyte prostaglandin synthesis is enhanced by IL-1

Keratinocytes are a rich source of IL-1, a cytokine which stimulates prostaglandin synthesis in many cell types. The effects on arachidonic acid metabolism of this cytokine were therefore studied in cultured adult human keratinocytes. Exogenous IL-1 increased basal cellular prostaglandin synthesis (particularly PGE2) threefold. Increased PGE2 synthesis in response to IL-1 was inhibited by cycloheximide, suggesting a requirement for new protein synthesis. Irradiation of the keratinocytes with low-dose ultraviolet light B (UVB) resulted in the release of increased quantities of both IL-1 and PGE2. The amount of IL-1 released was sufficient to increase PGE2 synthesis when exogenously added to unstimulated cells, suggesting a causal relationship. The time course of accumulation of IL-1 and PGE2 in the medium of irradiated keratinocytes was also consistent with a cause-effect relationship. No feedback inhibition of IL-1 release by the increased PGE2 was detected as demonstrated by the observation that IL-1 production in response to UVB was not augmented by treatment with indomethacin or blunted by the exogenous addition of PGE2. These data suggest that keratinocyte IL-1 may be partially responsible for induction of keratinocyte PGE2 synthesis after UVB irradiation.