Collagen XVII Shedding Suppresses Re-Epithelialization by Directing Keratinocyte Migration and Dampening mTOR Signaling

Collagen XVII promotes dormancy of colorectal cancer cells by activating mTORC2 signaling

Tumor dormancy is the underpinning for cancer relapse and chemoresistance, leading to massive cancer-related death in colorectal cancer (CRC). However, our comprehension of the mechanisms dictating tumor dormancy and strategies for eliminating dormant tumor cells remains restricted. In this study, we identified that collagen XVII (COL17A1), a hemidesmosomal transmembrane protein, can promote the dormancy of CRC cells. The upregulation of COL17A1 was observed to prolong quiescence periods and diminish drug susceptibility of CRC cells. Mechanistically, COL17A1 acts as a scaffold, enhancing the crosstalk between mTORC2 and Akt, thereby instigating the mTORC2-mediated dormant signaling. Notably, the activation of mTORC2 is contingent upon the intracellular domain of COL17A1, regardless of its ectodomain shedding. Our findings underscore a pivotal role of the COL17A1-mTORC2 axis in CRC dormancy, suggesting that mTORC2-specific inhibitors may hold therapeutic prospects for the eradication of dormant tumor cells.

Collagen 17A1 in the Urothelium Regulates Epithelial Cell Integrity and Local Immunologic Responses in Obstructive Uropathy

Collagen 17A1 (COL17A1), an epidermal hemidesmosome component, is ectopically induced in the urothelium of mouse and human renal pelvis (RP) in parallel with urinary tract-associated lymphoid structure development. Here, we found that COL17A1 was induced in obstructive uropathy-prone ureter of humans and cats. To ascertain its function, murine urinary organs with unilateral ureteral obstruction (UUO) were analyzed during 1 week after surgery. One day after UUO, COL17A1 expression increased in urothelial cells of RP and ureter, and was positively correlated with renal tubulointerstitial lesions. A portion of RP where the smooth muscle layer from the ureter was interrupted was sensitive to urothelium deciduation and COL17A1 induction, showing urine leaked from the RP lumen into the parenchyma. After urine stimulation, cultured immune cells expressed Cxcl2, also up-regulated in CD11b+ cells following COL17A1 stimulation. One day after UUO, CXCL2+ CD11b+ cells infiltrated the urothelium-disrupted area; however, these numbers were significantly lower in Col17a1-deficient mice. COL17A1+ urothelial cells partially co-expressed cytokeratin-14, a progenitor cell marker for urothelium, whereas Col17a1-deficient mice had lower numbers of cytokeratin-14+ cells. Gene Ontology analysis revealed that expression of epithelial- and immune-associated genes was up-regulated and down-regulated, respectively, in the ureter of Col17a1-deficient mice 4 days after UUO. Thus, COL17A1 maintains urothelium integrity by regulating urothelial cell adhesion, proliferation, and differentiation, and activates local immune responses during obstructive uropathy in mammals.

The Impact of Ultrashort Pulse Laser Structuring of Metals on In-Vitro Cell Adhesion of Keratinocytes

Besides the need for biomaterial surface modification to improve cellular attachment, laser-structuring is favorable for designing a new surface topography for external bone fixator pins or implants. The principle of this study was to observe how bioinspired (deer antler) laser-induced nano-microstructures influenced the adhesion and growth of skin cells. The goal was to create pins that allow the skin to attach to the biomaterial surface in a bacteria-proof manner. Therefore, typical fixator metals, steel, and titanium alloy were structured using ultrashort laser pulses, which resulted in periodical nano- and microstructures. Surface characteristics were investigated using a laser scanning microscope and static water contact angle measurements. In vitro studies with human HaCaT keratinocytes focused on cell adhesion, morphology, actin formation, and growth within 7 days. The study showed that surface functionalization influenced cell attachment, spreading, and proliferation. Micro-dimple clusters on polished bulk metals (DC20) will not hinder viability. Still, they will not promote the initial adhesion and spreading of HaCaTs. In contrast, additional nanostructuring with laser-induced periodic surface structures (LIPSS) promotes cell behavior. DC20 + LIPSS induced enhanced cell attachment with well-spread cell morphology. Thus, the bioinspired structures exhibited a benefit in initial cell adhesion. Laser surface functionalization opens up new possibilities for structuring, and is relevant to developing bioactive implants in regenerative medicine.

Collagen XVII regulates tumor growth in pancreatic cancer through interaction with the tumor microenvironment

Expression of the gene for collagen XVII (COL17A1) in tumor tissue is positively or negatively associated with patient survival depending on cancer type. High COL17A1 expression is thus a favorable prognostic marker for breast cancer but unfavorable for pancreatic cancer. This study explored the effects of COL17A1 expression on pancreatic tumor growth and their underlying mechanisms. Analysis of published single-cell RNA-sequencing data for human pancreatic cancer tissue revealed that COL17A1 was expressed predominantly in cancer cells rather than surrounding stromal cells. Forced expression of COL17A1 did not substantially affect the proliferation rate of the mouse pancreatic cancer cell lines KPC and AK4.4 in vitro. However, in mouse homograft tumor models in which KPC or AK4.4 cells were injected into syngeneic C57BL/6 or FVB mice, respectively, COL17A1 expression promoted or suppressed tumor growth, respectively, suggesting that the effect of COL17A1 on tumor growth was influenced by the tumor microenvironment. RNA-sequencing analysis of tumor tissue revealed effects of COL17A1 on gene expression profiles (including the expression of genes related to cell proliferation, the immune response, Wnt signaling, and Hippo signaling) that differed between C57BL/6-KPC and FVB-AK4.4 tumors. Our data thus suggest that COL17A1 promotes or suppresses cancer progression in a manner dependent on the interaction of tumor cells with the tumor microenvironment.

Mechanotransduction through hemidesmosomes during aging and longevity

Hemidesmosomes are structural protein complexes localized at the interface of tissues with high mechanical demand and shear forces. Beyond tissue anchoring, hemidesmosomes have emerged as force-modulating structures important for translating mechanical cues into biochemical and transcriptional adaptation (i.e. mechanotransduction) across tissues. Here, we discuss the recent insights into the roles of hemidesmosomes in age-related tissue regeneration and aging in C. elegans, mice and humans. We highlight the emerging concept of preserved dynamic mechanoregulation of hemidesmosomes in tissue maintenance and healthy aging.

Junctional epithelium and hemidesmosomes: Tape and rivets for solving the "percutaneous device dilemma" in dental and other permanent implants

The percutaneous device dilemma describes etiological factors, centered around the disrupted epithelial tissue surrounding non-remodelable devices, that contribute to rampant percutaneous device infection. Natural percutaneous organs, in particular their extracellular matrix mediating the "device"/epithelium interface, serve as exquisite examples to inspire longer lasting long-term percutaneous device design. For example, the tooth's imperviousness to infection is mediated by the epithelium directly surrounding it, the junctional epithelium (JE). The hallmark feature of JE is formation of hemidesmosomes, cell/matrix adhesive structures that attach surrounding oral gingiva to the tooth's enamel through a basement membrane. Here, the authors survey the multifaceted functions of the JE, emphasizing the role of the matrix, with a particular focus on hemidesmosomes and their five main components. The authors highlight the known (and unknown) effects dental implant - as a model percutaneous device - placement has on JE regeneration and synthesize this information for application to other percutaneous devices. The authors conclude with a summary of bioengineering strategies aimed at solving the percutaneous device dilemma and invigorating greater collaboration between clinicians, bioengineers, and matrix biologists.

The basement membrane in epidermal polarity, stemness, and regeneration

The epidermis is a specialized epithelium that constitutes the outermost layer of the skin, and it provides a protective barrier against environmental assaults. Primarily consisting of multilayered keratinocytes, the epidermis is continuously renewed by proliferation of stem cells and the differentiation of their progeny, which undergo terminal differentiation as they leave the basal layer and move upward toward the surface, where they die and slough off. Basal keratinocytes rest on a basement membrane at the dermal-epidermal junction that is composed of specific extracellular matrix proteins organized into interactive and mechanically supportive networks. Firm attachment of basal keratinocytes, and their dynamic regulation via focal adhesions and hemidesmosomes, is essential for maintaining major skin processes, such as self-renewal, barrier function, and resistance to physical and chemical stresses. The adhesive integrin receptors expressed by epidermal cells serve structural, signaling, and mechanosensory roles that are critical for epidermal cell anchorage and tissue homeostasis. More specifically, the basement membrane components play key roles in preserving the stem cell pool, and establishing cell polarity cues enabling asymmetric cell divisions, which result in the transition from a proliferative basal cell layer to suprabasal cells committed to terminal differentiation. Finally, through a well-regulated sequence of synthesis and remodeling, the components of the dermal-epidermal junction play an essential role in regeneration of the epidermis during skin healing. Here too, they provide biological and mechanical signals that are essential to the restoration of barrier function.

Tapping basement membrane motifs: Oral junctional epithelium for surface-mediated soft tissue attachment to prevent failure of percutaneous devices

Teeth, long-lasting percutaneous organs, feature soft tissue attachment through adhesive structures, hemidesmosomes, in the junctional epithelium basement membrane adjacent to teeth. This soft tissue attachment prevents bacterial infection of the tooth despite the rich - and harsh - microbial composition of the oral cavity. Conversely, millions of percutaneous devices (catheters, dental, and orthopedic implants) fail from infection yearly. Standard of care antibiotic usage fuels antimicrobial resistance and is frequently ineffective. Infection prevention strategies, like for dental implants, have failed in generating durable soft tissue adhesion - like that seen with the tooth - to prevent bacterial colonization at the tissue-device interface. Here, inspired by the impervious natural attachment of the junctional epithelium to teeth, we synthesized four cell adhesion peptide (CAPs) nanocoatings, derived from basement membranes, to promote percutaneous device soft tissue attachment. The two leading nanocoatings upregulated integrin-mediated hemidesmosomes, selectively increased keratinocyte proliferation compared to fibroblasts, which cannot form hemidesmosomes, and expression of junctional epithelium adhesive markers. CAP nanocoatings displayed marked durability under simulated clinical conditions and the top performer CAP nanocoating was validated in a percutaneous implant murine model. Basement membrane CAP nanocoatings, inspired by the tooth and junctional epithelium, may provide an alternative anti-infective strategy for percutaneous devices to mitigate the worldwide threat of antimicrobial resistance. STATEMENT OF SIGNIFICANCE: Prevention and management of medical device infection is a significant healthcare challenge. Overzealous antibiotic use has motivated alternative material innovations to prevent infection. Here, we report implant cell adhesion peptide nanocoatings that mimic a long-lasting, natural "medical device," the tooth, through formation of cell adhesive structures called hemidesmosomes. Such nanocoatings sidestep the use of antimicrobial or antibiotic elements to form a soft-tissue seal around implants. The top performing nanocoatings prompted expression of hemidesmosomes and defensive factors to mimic the tooth and was validated in an animal model. Application of cell adhesion peptide nanocoatings may provide an alternative to preventing, rather that necessarily treating, medical device infection across a range of device indications, like dental implants.

BP180/Collagen XVII: A Molecular View

BP180 is a type II collagenous transmembrane protein and is best known as the major autoantigen in the blistering skin disease bullous pemphigoid (BP). The BP180 trimer is a central component in type I hemidesmosomes (HD), which cause the adhesion between epidermal keratinocytes and the basal lamina, but BP180 is also expressed in several non-HD locations, where its functions are poorly characterized. The immunological roles of intact and proteolytically processed BP180, relevant in BP, have been subject to intensive research, but novel functions in cell proliferation, differentiation, and aging have also recently been described. To better understand the multiple physiological functions of BP180, the focus should return to the protein itself. Here, we comprehensively review the properties of the BP180 molecule, present new data on the biochemical features of its intracellular domain, and discuss their significance with regard to BP180 folding and protein-protein interactions.

EGFR-mediated epidermal stem cell motility drives skin regeneration through COL17A1 proteolysis

Skin regenerative capacity declines with age, but the underlying mechanisms are largely unknown. Here we demonstrate a functional link between epidermal growth factor receptor (EGFR) signaling and type XVII collagen (COL17A1) proteolysis on age-associated alteration of keratinocyte stem cell dynamics in skin regeneration. Live-imaging and computer simulation experiments predicted that human keratinocyte stem cell motility is coupled with self-renewal and epidermal regeneration. Receptor tyrosine kinase array identified the age-associated decline of EGFR signaling in mouse skin wound healing. Culture experiments proved that EGFR activation drives human keratinocyte stem cell motility with increase of COL17A1 by inhibiting its proteolysis through the secretion of tissue inhibitor of metalloproteinases 1 (TIMP1). Intriguingly, COL17A1 directly regulated keratinocyte stem cell motility and collective cell migration by coordinating actin and keratin filament networks. We conclude that EGFR-COL17A1 axis-mediated keratinocyte stem cell motility drives epidermal regeneration, which provides a novel therapeutic approach for age-associated impaired skin regeneration.

Collagen XVII inhibits breast cancer cell proliferation and growth through deactivation of the AKT/mTOR signaling pathway

Collagen XVII (COL17), a cell-matrix adhesion protein, has been found to be suppressed in breast cancer. Our previous data demonstrated a preventive role of COL17 in breast cancer invasiveness. The present study used the stable COL17-overexpressing MCF7 and MDA-MB-231 cells to reveal an anti-proliferative effect of COL17 on breast cancer cell through mTOR deactivation. Cell proliferation was negatively correlated with the expression level of COL17 in a concentration-dependent manner in both conventional and three-dimensional (3D) culture systems. The correlation was confirmed by decreased expression of the proliferative marker Ki67 in COL17-expressing cells. In addition, overexpression of COL17 reduced the clonogenicity and growth of the cells. We demonstrated that COL17 affects the AKT/mTOR signaling pathway by deactivation of AKT, mTOR and downstream effectors, particularly 4EBP1. Moreover, mice xenografted with high COL17-expressing cells exhibited delayed tumor progression and prolonged survival time. The high expression of COL17A1 gene encoding COL17 is associated with low-proliferation tumors, extended tumor-free period, and overall survival of breast cancer patients. In conclusion, our results revealed the novel function of COL17 using in vitro and in vivo models and elucidated the related pathway in breast cancer cell growth and proliferation.

Focal adhesion dynamics in cellular function and disease

Acting as a bridge between the cytoskeleton of the cell and the extra cellular matrix (ECM), the cell-ECM adhesions with integrins at their core, play a major role in cell signalling to direct mechanotransduction, cell migration, cell cycle progression, proliferation, differentiation, growth and repair. Biochemically, these adhesions are composed of diverse, yet an organised group of structural proteins, receptors, adaptors, various enzymes including protein kinases, phosphatases, GTPases, proteases, etc. as well as scaffolding molecules. The major integrin adhesion complexes (IACs) characterised are focal adhesions (FAs), invadosomes (podosomes and invadopodia), hemidesmosomes (HDs) and reticular adhesions (RAs). The varied composition and regulation of the IACs and their signalling, apart from being an integral part of normal cell survival, has been shown to be of paramount importance in various developmental and pathological processes. This review per-illustrates the recent advancements in the research of IACs, their crucial roles in normal as well as diseased states. We have also touched on few of the various methods that have been developed over the years to visualise IACs, measure the forces they exert and study their signalling and molecular composition. Having such pertinent roles in the context of various pathologies, these IACs need to be understood and studied to develop therapeutical targets. We have given an update to the studies done in recent years and described various techniques which have been applied to study these structures, thereby, providing context in furthering research with respect to IAC targeted therapeutics.

Epidermolysis bullosa

Epidermolysis bullosa (EB) is an inherited, heterogeneous group of rare genetic dermatoses characterized by mucocutaneous fragility and blister formation, inducible by often minimal trauma. A broad phenotypic spectrum has been described, with potentially severe extracutaneous manifestations, morbidity and mortality. Over 30 subtypes are recognized, grouped into four major categories, based predominantly on the plane of cleavage within the skin and reflecting the underlying molecular abnormality: EB simplex, junctional EB, dystrophic EB and Kindler EB. The study of EB has led to seminal advances in our understanding of cutaneous biology. To date, pathogenetic mutations in 16 distinct genes have been implicated in EB, encoding proteins influencing cellular integrity and adhesion. Precise diagnosis is reliant on correlating clinical, electron microscopic and immunohistological features with mutational analyses. In the absence of curative treatment, multidisciplinary care is targeted towards minimizing the risk of blister formation, wound care, symptom relief and specific complications, the most feared of which - and also the leading cause of mortality - is squamous cell carcinoma. Preclinical advances in cell-based, protein replacement and gene therapies are paving the way for clinical successes with gene correction, raising hopes amongst patients and clinicians worldwide.

Transmembrane collagens-Unexplored mediators of epidermal-dermal communication and tissue homeostasis

Tissue homeostasis is maintained through constant, dynamic and heterogeneous communication between cells and their microenvironment. Proteins that are at the same time active at the intracellular, cell periphery and deeper extracellular levels possess the ability to, on the individual molecular level, influence the cells and their microenvironment in a bidirectional manner. The transmembrane collagens are a family of such proteins, which are of notable interest for tissue development and homeostasis. In skin, expression of all transmembrane collagens has been reported and deficiency of transmembrane collagen XVII manifests with distinct skin phenotypes. Nevertheless, transmembrane collagens in skin remain understudied despite the association of them with epidermal wound healing and dermal fibrotic processes. Here, we present an overview of transmembrane collagens and put a spotlight on them as regulators of epidermal-dermal communication and as potential players in fibrinogenesis.

Composition of hemidesmosomes in basal keratinocytes of normal buccal mucosa and oral lichen planus

Oral lichen planus (OLP) is a chronic inflammatory disease displaying ultrastructural disturbances in epithelial hemidesmosomes. The expression of several key hemidesmosomal components in OLP as well as in normal buccal mucosa is, however, unknown. The aim of the study was therefore to examine intracellular and extracellular components involved in hemidesmosomal attachment, in OLP (n = 20) and in normal buccal mucosa (n = 10), by immunofluorescence. In normal buccal mucosa, laminin-α3γ2, integrin-α6β4, CD151, collagen α-1(XVII) chain, and dystonin showed linear expression along the basal membrane, indicating the presence of type I hemidesmosomes. Plectin stained most epithelial cell membranes and remained unphosphorylated at S4642. In OLP, most hemidesmosomal molecules examined showed disturbed expression consisting of discontinuous increases, apicolateral location, and/or intracellular accumulation. Plectin showed S4642-phosphorylation at the basement membrane, and deposits of laminin-α3 and laminin-γ2 were found within the connective tissue. The disturbed expression of hemidesmosomal proteins in OLP indicates deficient attachment of the basal cell layer, which can contribute to detachment and cell death of basal keratinocytes seen in the disease.

The Pathobiology of Skin Aging: New Insights into an Old Dilemma

Long considered both physiologic and inevitable, skin aging is a degenerative phenomenon whereby both intrinsic and environmental factors conspire to produce an authentic disease. The consequences of this disorder are many and varied, ranging from atrophy and fragility to defective repair to deficient immunity and vulnerability to certain infections. The pathobiologic basis for skin aging remains poorly understood. At a cellular level, stem cell dysfunction and attrition appear to be key events, and both genetic and epigenetic factors are involved in a complex interplay that over time results in deterioration of our main protective interface with the external environment. Past and current understanding of the cellular and molecular intricacies of skin aging provide a foundation for future approaches designed to thwart the aging phenotype. Herein, the authors provide a review of current insights into skin aging, including the mechanisms of skin aging, the role of stem cells in skin aging and the implications of skin aging for the microbiome and for the development of cancer. Conquest of the oft overlooked disease of skin aging should have broad implications that transcend the integument and inform novel approaches to retarding aging and age-related dysfunction in those internal organs that youthful skin was designed to envelop and safeguard.

USP15 Enhances Re-epithelialization Through Deubiquitinating EIF4A1 During Cutaneous Wound Repair

Re-epithelialization is a fundamental process in wound healing that involves various cytokines and cells during cutaneous barrier reconstruction. Ubiquitin-specific peptidase 15 (USP15), an important member of the deubiquitinating enzymes (DUBs), removes ubiquitin chains from target proteins and maintains protein stability. However, the dynamic role of USP15 in epithelialization remains unclear. We aimed to investigate the regulatory function of USP15 in re-epithelialization. An excisional wound splinting model was established to evaluate the re-epithelialization rate in Usp15 knockout (KO) mice. Coimmunoprecipitation (Co-IP) and mass spectrum analyses were performed to identify USP15-interacting proteins. RNA-sequencing was performed for transcriptome analysis in keratinocytes and uploaded into NODE database (http://www.biosino.org/node, accession numbers: OEP000770 and OEP000763). First, a significant delay in epithelialization was observed in the Usp15 KO mice. Moreover, inhibition of cell migration and proliferation was observed in the USP15-silenced keratinocytes (HaCaTs). Moreover, we revealed for the first time that USP15 could interact with eukaryotic initiation factor 4A-1 (EIF4A1), thereby promoting translational efficacy in keratinocytes, which is essential for keratinocyte proliferation and migration. Conclusively, the USP15-EIF4A1 complex significantly accelerated re-epithelialization in wound healing. These observations helped elucidate the function and mechanisms of USP15 in modulating re-epithelialization in wound healing, providing a promising target for refractory wound treatment.

Skin proteomics - analysis of the extracellular matrix in health and disease

INTRODUCTION

The skin protects the human body from external insults and regulates water and temperature homeostasis. A highly developed extracellular matrix (ECM) supports the skin and instructs its cell functions. Reduced functionality of the ECM is often associated with skin diseases that cause physical impairment and also have implications on social interactions and quality of life of affected individuals.

AREAS COVERED

With a focus on the skin ECM we discuss how mass spectrometry (MS)-based proteomic approaches first contributed to establishing skin protein inventories and then facilitated elucidation of molecular functions and disease mechanisms.

EXPERT OPINION

MS-based proteomic approaches have significantly contributed to our understanding of skin pathophysiology, but also revealed the challenges in assessing the skin ECM. The numerous posttranslational modifications of ECM proteins, like glycosylation, crosslinking, oxidation, and proteolytic maturation in disease settings can be difficult to tackle and remain understudied. Increased ease of handling of LC-MS/MS systems and automated/streamlined data analysis pipelines together with the accompanying increased usage of LC-MS/MS approaches will ensure that in the coming years MS-based proteomic approaches will continue to play a vital part in skin disease research. They will facilitate the elucidation of molecular disease mechanisms and, ultimately, identification of new druggable targets.

Life before and beyond blistering: The role of collagen XVII in epidermal physiology

Type XVII collagen (COL17) is a transmembranous protein that is mainly expressed in the epidermal basal keratinocytes. Epidermal-dermal attachment requires COL17 expression at the hemidesmosomes of the epidermal basement membrane zone because congenital COL17 deficiency leads to junctional epidermolysis bullosa and acquired autoimmunity to COL17 induces bullous pemphigoid. Recently, in addition to facilitating epidermal-dermal attachment, COL17 has been reported to serve as a niche for hair follicle stem cells, to regulate proliferation in the interfollicular epidermis and to be present along the non-hemidesmosomal plasma membrane of epidermal basal keratinocytes. This review focuses on the physiological properties of COL17 in the epidermis, its role in maintaining stem cells and its association with signalling pathways. We propose possible solutions to unanswered questions in this field.

Amino acid substitution in the C-terminal domain of collagen XVII reduces laminin-332 interaction causing mild skin fragility with atrophic scarring

The behavior of a cell depends on how its adhesion molecules interact with the cellular microenvironment. Hemidesmosomal collagen XVII essentially contributes to cell adhesion and modulates keratinocyte directionality and proliferation during skin regeneration, however only little is known about the involved interactions. Here, we used keratinocytes from patients with junctional epidermolysis bullosa with late onset, which exclusively produce a collagen XVII mutant with the p.R1303Q mutation within its extracellular C-terminus. Although this mutant was normally expressed and targeted to the membrane and the expression of integrins α3β1, α6β4 and of laminin-332 was unchanged, the keratinocytes were less adhesive, showed migratory defects and decreased clonogenic growth. Since the p.R1303Q substitution is located within the predicted laminin-332 binding site of collagen XVII, we anticipated an altered collagen XVII-laminin-332 interaction. Indeed, the pR1303Q collagen XVII ectodomain showed decreased binding capability to laminin-332 and was less co-localized with pericellular laminin-332 molecules in cell culture. Thus, aberrant collagen XVII-laminin-332 interaction results in reduced cell adhesion, destabilized cell motility and decreased clonogenicity, which in turn lead to blister formation, delayed wound healing and skin atrophy.

CTBP1 depletion on prostate tumors deregulates miRNA/mRNA expression and impairs cancer progression in metabolic syndrome mice

About 20% of prostate cancer (PCa) patients progress to metastatic disease. Metabolic syndrome (MeS) is a pathophysiological disorder that increases PCa risk and aggressiveness. C-terminal binding protein (CTBP1) is a transcriptional corepressor that is activated by high-fat diet (HFD). Previously, our group established a MeS/PCa mice model that identified CTBP1 as a novel link associating both diseases. Here, we integrated in vitro (prostate tumor cell lines) and in vivo (MeS/PCa NSG mice) models with molecular and cell biology techniques to investigate MeS/CTBP1 impact over PCa progression, particularly over cell adhesion, mRNA/miRNA expression and PCa spontaneous metastasis development. We found that CTBP1/MeS regulated expression of genes relevant to cell adhesion and PCa progression, such as cadherins, integrins, connexins, and miRNAs in PC3 xenografts. CTBP1 diminished PCa cell adhesion, membrane attachment to substrate and increased filopodia number by modulating gene expression to favor a mesenchymal phenotype. NSG mice fed with HFD and inoculated with CTBP1-depleted PC3 cells, showed a decreased number and size of lung metastases compared to control. Finally, CTBP1 and HFD reduce hsa-mir-30b-5p plasma levels in mice. This study uncovers for the first time the role of CTBP1/MeS in PCa progression and its molecular targets.

Enhancement of Cutaneous Wound Healing by Dsg2 Augmentation of uPAR Secretion

In addition to playing a role in adhesion, desmoglein 2 (Dsg2) is an important regulator of growth and survival signaling pathways, cell proliferation, migration and invasion, and oncogenesis. Although low-level Dsg2 expression is observed in basal keratinocytes and is downregulated in nonhealing venous ulcers, overexpression has been observed in both melanomas and nonmelanoma malignancies. Here, we show that transgenic mice overexpressing Dsg2 in basal keratinocytes primed the activation of mitogenic pathways, but did not induce dramatic epidermal changes or susceptibility to chemical-induced tumor development. Interestingly, acceleration of full-thickness wound closure and increased wound-adjacent keratinocyte proliferation was observed in these mice. As epidermal cytokines and their receptors play critical roles in wound healing, Dsg2-induced secretome alterations were assessed with an antibody profiler array and revealed increased release and proteolytic processing of the urokinase-type plasminogen activator receptor. Dsg2 induced urokinase-type plasminogen activator receptor expression in the skin of transgenic compared with wild-type mice. Wounding further enhanced urokinase-type plasminogen activator receptor in both epidermis and dermis with a concomitant increase in the prohealing laminin-332, a major component of the basement membrane zone, in transgenic mice. This study demonstrates that Dsg2 induces epidermal activation of various signaling cascades and accelerates cutaneous wound healing, in part, through urokinase-type plasminogen activator receptor-related signaling cascades.

Epidermolysis bullosa: Molecular pathology of connective tissue components in the cutaneous basement membrane zone

Epidermolysis bullosa (EB), a group of heritable skin fragility disorders, is characterized by blistering, erosions and chronic ulcers in the skin and mucous membranes. In some forms, the blistering phenotype is associated with extensive mutilating scarring and development of aggressive squamous cell carcinomas. The skin findings can be associated with extracutaneous manifestations in the ocular as well as gastrointestinal and vesico-urinary tracts. The phenotypic heterogeneity reflects the presence of mutations in as many as 20 different genes expressed in the cutaneous basement membrane zone, and the types and combinations of the mutations and their consequences at the mRNA and protein levels contribute to the spectrum of severity encountered in different subtypes of EB. This overview highlights the molecular genetics of EB based on mutations in the genes encoding type VII and XVII collagens as well as laminin-332. The mutations identified in these protein components of the extracellular matrix attest to their critical importance in providing stability to the cutaneous basement membrane zone, with implications for heritable and acquired diseases.

Matrix molecules and skin biology

An extracellular matrix (ECM) is a prerequisite for multicellular life. It is adapted to tissues and constantly undergoes changes to preserve microenvironmental homeostasis. The ECM acts as a structural scaffold that establishes tissue architecture and provides tensile strength. It has cell-instructive functions by serving as a reservoir and presenter of soluble agents, being directly signaling, integrating transmission of mechanical and biological cues, or serving as a co-factor potentiating signaling. The skin contains a highly developed, mechanically tough, but yet flexible ECM. The tissue-specific features of this ECM are largely attributed by minor ECM components. A large number of genetic and acquired ECM diseases with skin manifestations, provide an illustrative testament to the importance of correct assembly of the ECM for dermal homeostasis. Here, we will present the composition and features of the skin ECM during homeostasis and regeneration. We will discuss genetic and acquired ECM diseases affecting skin, and provide a short outlook to therapeutic strategies for them.

Extracellular matrix contribution to skin wound re-epithelialization

The ability of skin to act as a barrier is primarily determined by cells that maintain the continuity and integrity of skin and restore it after injury. Cutaneous wound healing in adult mammals is a complex multi-step process that involves overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodeling. Under favorable conditions, epidermal regeneration begins within hours after injury and takes several days until the epithelial surface is intact due to reorganization of the basement membrane. Regeneration relies on numerous signaling cues and on multiple cellular processes that take place both within the epidermis and in other participating tissues. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here we focus on the involvement of the extracellular matrix proteins that impact epidermal regeneration during wound healing.

Targeting of Cell Surface Proteolysis of Collagen XVII Impedes Squamous Cell Carcinoma Progression

Squamous cell carcinoma (SCC) is one of the most common skin cancers and causes significant morbidity. Although the expression of the epithelial adhesion molecule collagen XVII (ColXVII) has been linked to SCC invasion, only little is known about its mechanistic contribution. Here, we demonstrate that ColXVII expression is essential for SCC cell proliferation and motility. Moreover, it revealed that particularly the post-translational modification of ColXVII by ectodomain shedding is the major driver of SCC progression, because ectodomain-selective immunostaining was mainly localized at the invasive front of human cutaneous SCCs, and exclusive expression of a non-sheddable ColXVII mutant in SCC-25 cells inhibits their matrix-independent growth and invasiveness. This cell surface proteolysis, which is strongly elevated during SCC invasion and metastasis, releases soluble ectodomains and membrane-anchored endodomains. Both released ColXVII domains play distinct roles in tumor progression: the endodomain induces proliferation and survival, whereas the ectodomain accelerates invasiveness. Furthermore, specific blockage of shedding by monoclonal ColXVII antibodies repressed matrix-independent growth and invasion of SCC cells in organotypic co-cultures. Thus, selective inhibition of ColXVII shedding may offer a promising therapeutic strategy to prevent SCC progression.

BP180 Is Critical in the Autoimmunity of Bullous Pemphigoid

Bullous pemphigoid (BP) is by far the most common autoimmune blistering dermatosis that mainly occurs in the elderly. The BP180 is a transmembrane glycoprotein, which is highly immunodominant in BP. The structure and location of BP180 indicate that it is a significant autoantigen and plays a key role in blister formation. Autoantibodies from BP patients react with BP180, which leads to its degradation and this has been regarded as the central event in BP pathogenesis. The consequent blister formation involves the activation of complement-dependent or -independent signals, as well as inflammatory pathways induced by BP180/anti-BP180 autoantibody interaction. As a multi-epitope molecule, BP180 can cause dermal-epidermal separation via combining each epitope with specific immunoglobulin, which also facilitates blister formation. In addition, some inflammatory factors can directly deplete BP180, thereby leading to fragility of the dermal-epidermal junction and blister formation. This review summarizes recent investigations on the role of BP180 in BP pathogenesis to determine the potential targets for the treatment of patients with BP.

IgE autoreactivity in bullous pemphigoid: eosinophils and mast cells as major targets of pathogenic immune reactants

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune disease characterized by tense blisters that are usually preceded by urticarial eruptions. Affected patients exhibit IgG and/or IgE autoantibodies against BP180 and/or BP230. Their relative importance in disease pathogenesis has not been fully elucidated.

OBJECTIVES

The aim of this study was to provide a better characterization of the circulating and tissue-resident IgE in patients with BP at the serological, structural and functional levels.

METHODS

Sera (n = 19) and skin (n = 33) from patients with BP were analysed via enzyme-linked immunosorbent assay (ELISA) and immunofluorescence, respectively.

RESULTS

The results obtained show that many patients with BP exhibit elevated IgE levels in the serum and in the skin. In the skin, it is very rarely and only sparsely found along the basement membrane zone, but is prominently present on mast cells and eosinophils. At least a portion of these IgE antibodies are BP-specific, as evidenced by serum ELISA and by the colocalization of BP180 and FcεRI-bound IgE on mast cells and/or eosinophils. An important role of these immune reactants can be inferred from our additional finding that cross-linking of IgE, derived from BP sera, on FcεRI-expressing rat basophils with BP180 results in robust degranulation of these cells.

CONCLUSIONS

We propose the existence of a disease pathway alternative to IgG and complement that may well be responsible for some of the clinical features of this autoimmune disease.

Identification of tissue damage, extracellular matrix remodeling and bacterial challenge as common mechanisms associated with high-risk cutaneous squamous cell carcinomas

In this study we used a genetic extracellular matrix (ECM) disease to identify mechanisms associated with aggressive behavior of cutaneous squamous cell carcinoma (cSCC). cSCC is one of the most common malignancies and usually has a good prognosis. However, some cSCCs recur or metastasize and cause significant morbidity and mortality. Known factors that are associated with aggressiveness of cSCCs include tumor grading, size, localization and microinvasive behavior. To investigate molecular mechanisms that influence biologic behavior we used global proteomic and histologic analyses of formalin-fixed paraffin-embedded tissue of primary human cSCCs. We compared three groups: non-recurring, non-metastasizing low-risk sporadic cSCCs; metastasizing sporadic cSCCs; and cSCCs from patients with recessive dystrophic epidermolysis bullosa (RDEB). RDEB is a genetic skin blistering and ECM disease caused by collagen VII deficiency. Patients commonly suffer from high-risk early onset cSCCs that frequently metastasize. The results indicate that different processes are associated with formation of RDEB cSCCs compared to sporadic cSCCs. Sporadic cSCCs show signs of UV damage, whereas RDEB cSCCs have higher mutational rates and display tissue damage, inflammation and subsequent remodeling of the dermal ECM as tumor initiating factors. Interestingly the two high-risk groups - high-risk metastasizing sporadic cSCCs and RDEB cSCCs - are both associated with tissue damage and ECM remodeling in gene-ontology enrichment and Search Tool for the Retrieval of Interacting Genes/Proteins analyses. In situ histologic analyses validate these results. The high-risk cSCCs also show signatures of enhanced bacterial challenge. Histologic analyses confirm correlation of bacterial colonization with worse prognosis. Collectively, this unbiased study - performed directly on human patient material - reveals that common microenvironmental alterations linked to ECM remodeling and increased bacterial challenges are denominators of high-risk cSCCs. The proteins identified here could serve as potential diagnostic markers and therapeutic targets in high-risk cSCCs.

Identification of a novel p53 target, COL17A1, that inhibits breast cancer cell migration and invasion

p53 mutation is a marker of poor prognosis in breast cancers. To identify downstream targets of p53, we screened two transcriptome datasets, including cDNA microarrays of MCF10A breast epithelial cells with wild-type p53 or p53-null background, and RNA sequence analysis of breast invasive carcinoma. Here, we unveil ten novel p53 target candidates that are up-regulated after the induction of p53 in wild-type cells. Their expressions are also high in breast invasive carcinoma tissues with wild-type p53. The GO analysis identified epidermis development and ectoderm development, which COL17A1 participates, as significantly up-regulated by wild-type p53. The COL17A1 expressions increased in a p53-dependent manner in human breast cells and mouse mammary tissues. Reporter assay and ChIP assay identified intronic p53-binding sequences in the COL17A1 gene. The MDA-MB-231 cells that genetically over-express COL17A1 gene product exhibited reduced migration and invasion in vitro. Similarly, COL17A1 expression was decreased in metastatic tumors compared to primary tumors and normal tissues, even from the same patients. Moreover, high COL17A1 expression was associated with longer survival of patients with invasive breast carcinoma. In conclusion, we revealed that COL17A1 is a novel p53 transcriptional target in breast tissues that inhibits cell migration and invasion and is associated with better prognosis.

Amino acid duplication in the coiled-coil structure of collagen XVII alters its maturation and trimerization causing mild junctional epidermolysis bullosa

The function and stability of collagens depend on the accurate triple helix formation of three distinct polypeptide chains. Disruption of this triple-helical structure can result in connective-tissue disorders. Triple helix formation is thought to depend on three-stranded coiled-coil oligomerization sites within non-collagenous domains. However, only little is known about the physiological relevance of these coiled-coil structures. Transmembrane collagen XVII, also known as 180 kDa bullous pemphigoid antigen provides mechanical stability through the anchorage of epithelial cells to the basement membrane. Mutations in the collagen XVII gene, COL17A1, cause junctional epidermolysis bullosa (JEB), characterized by chronic trauma-induced skin blistering. Here we exploited a novel naturally occurring COL17A1 mutation, leading to an in-frame lysine duplication within the coiled-coil structure of the juxtamembranous NC16A domain of collagen XVII, which resulted in a mild phenotype of JEB due to reduced membrane-anchored collagen XVII molecules. This mutation causes structural changes in the mutant molecule and interferes with its maturation. The destabilized coiled-coil structure of the mutant collagen XVII unmasks a furin cleavage site that results in excessive and non-physiological ectodomain shedding during its maturation. Furthermore, it decreases its triple-helical stability due to defective coiled-coil oligomerization, which makes it highly susceptible to proteolytic degradation. As a consequence of altered maturation and decreased stability of collagen XVII trimers, reduced collagen XVII is incorporated into the cell membrane, resulting in compromised dermal-epidermal adhesion. Taken together, using this genetic model, we provide the first proof that alteration of the coiled-coil structure destabilizes oligomerization and impairs physiological shedding of collagen XVII in vivo.

Tension in Cancer

Integrins represent a large family of cell receptors that mediate adhesion to the extracellular matrix (ECM), thereby modulating a variety of cellular functions that are required for proliferation, migration, malignant conversion and invasiveness. During tumorigenesis the conversion of a tumor cell from sessile, stationary phenotype to an invasive phenotype requires the ability of tumor cells to interact with their environment in order to transduce signals from the ECM into the cells. Hence, there is increasing evidence that changes in the composition, topography and tension of tumor matrix can be sensed by integrin receptors, leading to the regulation of intracellular signalling events which subsequently help to fuel cancer progression. The fact that intracellular signals perceived from integrin ligand binding impact on almost all steps of tumor progression, including tumor cell proliferation, survival, metastatic dissemination and colonization of a metastatic niche, renders integrins as ideal candidates for the development of therapeutic agents. In this review we summarize the role of integrins in cancer with the special focus on cancer therapies and the recent progress that has been made in the understanding of “integrin-induced tension in cancer”. Finally, we conclude with clinical evidence for the role of integrin-mediated mechanotransduction in the development of therapy-resistant tumors.