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At least 343 records · Page 19Linked to original sources
PubMed2006

Beta 4 integrin amplifies ErbB2 signaling to promote mammary tumorigenesis.

Amplification of the ErbB2 locus, which encodes a receptor tyrosine kinase, is common in aggressive breast tumors and correlates with poor prognosis. The mechanisms underlying ErbB2-mediated breast carcinoma progression remain incompletely defined. To examine the role of the signaling and cell-adhesion receptor beta 4 integrin during ErbB2-mediated tumorigenesis, we introduced a targeted deletion of the beta 4 signaling domain into a mouse model of ErbB2-induced mammary carcinoma. Loss of beta 4 signaling suppresses mammary tumor onset and invasive growth. Ex vivo studies indicate that beta 4 forms a complex with ErbB2 and enhances activation of the transcription factors STAT3 and c-Jun. STAT3 contributes to disruption of epithelial adhesion and polarity, while c-Jun is required for hyperproliferation. Finally, deletion of the beta 4 signaling domain enhances the efficacy of ErbB2-targeted therapy. These results indicate that beta 4 integrin promotes tumor progression by amplifying ErbB2 signaling and identify beta 4 as a potential target for molecular therapy of breast cancer.

Animals↗
PubMed2004

Infantile hemangioma is a proliferation of beta 4-negative endothelial cells adjacent to HLA-DR-positive cells with dendritic cell morphology.

Although hemangioma is referred as to the most common tumor in infancy, the underlying pathogenetic events and the biologic origin of this benign vascular neoplasm have remained obscure. By using immunohistochemistry on frozen sections of infantile hemangiomas, we show here that proliferating endothelial cells abundantly expressed alpha(v)beta(3) but lacked beta(4) integrins. Instead, regressing and involuting infantile hemangiomas due to treatment with IFN-alpha showed positive staining of beta(4) integrin, which might point to the angiogenic significance of beta(4) integrin in infantile hemangiomas. Moreover, immunofluorescence analysis revealed the existence of HLA-DR(+), mostly CD68(+) and partly DC-SIGN/CD209(+) cells with dendritic cell morphology in the intimate vicinity of hemangiomatous vessels. Such cells were also detected in the dermal microvascular unit in normal skin. The coupled occurrence of vascular structures and perivascular cells that were stained positive with markers of monocyte or macrophage or dendritic cells might suggest that the development of infantile hemangioma is a result of vasculogenesis, that is, the formation of primitive blood vessels from angioblasts, rather than of angiogenesis, that is, the sprouting of capillaries from preexisting vessels.

Adolescent↗
PubMed1997

Cloning and sequence of the cDNA encoding the beta 4 integrin subunit in rat peripheral nerve.

beta 4 and alpha 6 integrin subunits dimerize to form an adhesion receptor that is necessary to nucleate hemidesmosomes and to anchor epithelial cells to their basal laminae. beta 4 is also expressed in Schwann cell (which do not contain hemidesmosomes) in peripheral nerve, where it may function in the formation or maintenance of myelin. The cDNA for beta 4 integrin has been cloned from epithelia-derived human and mouse tissues. We cloned cDNAs encoding beta 4 integrin from libraries derived from rat peripheral nerve, and determined the complete nucleotide sequence encoding the signal peptide and mature protein. Comparison of the deduced amino acid (aa) sequence revealed 95.1% and 87.5% identity with the mouse and human epithelia-derived sequences, respectively. The amino acid sequence of postulated signal transduction domains in beta 4 was 100% identical among rat, mouse, and human. Our cDNA clones included two of the four postulated alternatively spliced variants previously described in epithelial clones. Despite the potentially diverse functions of beta 4 integrin in Schwann cells and keratinocytes, the cDNAs for nerve-derived beta 4 integrin are highly similar to those cloned from epithelia.

Amino Acid Sequence↗
PubMed2003

Cleavage of corneal basement membrane components by ethanol exposure in laser-assisted subepithelial keratectomy.

PURPOSE: To determine the anatomic cleavage plane after exposure to 20% ethanol for approximately 20 to 25 seconds to create an epithelial flap in laser-assisted subepithelial keratectomy (LASEK). SETTING: Ocular Surface Research & Education Foundation, Miami, Florida, and Hermann Eye Center Refractive Surgery Center, Houston, Texas, USA. METHODS: Immunofluorescence staining using monoclonal antibodies against laminin 5, collagen VII, and integrins beta(1) and beta(4) was performed to determine the anatomic location of the cleavage plane in an epithelial flap created by 20-second exposure to 20% ethanol in cadaver eyes and in epithelial flaps obtained from LASEK patients. RESULTS: Immunofluorescence staining to laminin 5 and integrin beta(4) was patchy in the lifted flap and the remaining corneal basement membrane. Immunostaining to collagen VII, the main component of anchoring fibrils, remained exclusively in the corneal bed. Immunostaining to integrin beta(1), present in the pericellular location of all epithelial cell layers, remained exclusively in the epithelial flap. This finding was consistent in cadaver corneas and LASEK epithelial flaps. CONCLUSIONS: The cleavage plane of the ethanol-induced corneal epithelial flap is located between the lamina lucida and the lamina densa of the basement membrane, where integrin beta(4) interacts with laminin 5 to form hemidesmosomes.

Antibodies, Monoclonal↗
PubMed1997

Integrators of epidermal growth and differentiation: distinct functions for beta 1 and beta 4 integrins.

Mammalian epithelia are critically dependent on interactions with components in the underlying basal lamina for proper morphogenesis and function. Substratum attachment is essential for survival, proliferation, movement, and differentiation; detachment compromises the cell's ability to perform these functions, often resulting in human disease. Interactions with the extracellular matrix are mediated through transmembrane integrin receptors that transmit signals to the cytoskeleton and to signaling molecules within the proliferating cells of the epithelium. In the past year, novel insights have emerged regarding the specific role of integrins in their attachment to extracellular matrix and in their signal transduction pathways within the epidermis.

Animals↗
PubMed2001

Retooling of the beta 4 integrin in tumor cells--ligands lost and kinase gained.

In carcinoma cells, the beta 4 integrin functions in a ligand-independent manner to promote proliferation, migration, and invasion. An interesting new paper describes a mechanism whereby the beta 4 integrin cytoplasmic tail becomes an integrin ligand-independent adaptor protein for the Met receptor tyrosine kinase, thereby enhancing the mitogenic, morphogenic, and motogenic properties of Met.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Organotypic keratinocyte coculture using normal human serum: an immunomorphological study at light and electron microscopic levels.

Organotypic human skin equivalents of keratinocytes and fibroblasts embedded in collagen matrix have been the subject of studies dealing with various culture conditions. Development of standardized living skin equivalents using defined culture media containing respective supplements can provide important instruments of investigation in skin biology. In addition, tissue engineering has created human skin substitutes for treatment of acute and chronic wounds. In our study, we generate a modified organotypic human skin equivalent using normal human serum instead of fetal calf serum (FCS). This living skin equivalent shows regular stratification of the epidermis and the dermal-epidermal junction zone at the light and electron microscopic level after 1 and 3 weeks of coculture. Indirect immunofluorescence reveals regular expression of differentiation antigens and the major structural proteins collagen IV, laminin 5 and the integrin chains alpha 6 and beta 4 at the dermo-epidermal junction zone. Immunoelectron microscopy demonstrates expression of collagen IV, alpha 6 and beta 4 integrin after 1 and 3 weeks of coculture. This organotypic skin model could be the basis for autologous skin grafting for acute or chronic wounds using autologous serum as well as patients' keratinocytes and fibroblasts, thus minimizing the risk of transmitting infectious agents.

Animals↗
PubMed1996

Epithelial detachment due to absence of hemidesmosomes in integrin beta 4 null mice.

Integrins are heterodimeric transmembrane glycoproteins which are engaged in a variety of cellular functions, such as adhesion, migration and differentiation1. The integrin alpha 6 beta 4 is expressed on squamous epithelia, on subsets of endothelial cells, immature thymocytes and on Schwann cells and fibroblasts in the peripheral nervous system. In stratified epithelia, alpha 6 beta 4 is concentrated in specialised adhesion structures, called hemidesmosomes, which are implicated in the stable attachment of the basal cells to the underlying basement membrane by connecting the intermediate filaments with the extracellular matrix. The nature of the interactions between the various hemidesmosomal proteins, that lead to the formation of hemidesmosome is poorly understood. To study the contribution of the integrin alpha 6 beta 4 in hemidesmosome formation and their anchoring properties, we inactivated the beta 4 gene in mice by targeted gene disruption. Homozygous beta 4 null mice died shortly after birth and displayed extensive detachment of the epidermis and other squamous epithelia. The dramatically reduced adhesive properties of the skin was accompanied by the absence of hemidesmosomes at the basal surface of keratinocytes. No evidence was found for impaired T-cell development, nor for defects in myelination in the peripheral nervous system.

Animals↗
PubMed2006

Tissue transglutaminase expression promotes cell attachment, invasion and survival in breast cancer cells.

Distant metastasis is frequently observed in patients with breast cancer and is a major cause of cancer-related deaths in these patients. Currently, very little is known about the mechanisms that underlie the development of the metastatic phenotype in breast cancer cells. We previously found that metastatic breast cancer cells express high levels of tissue transglutaminase (TG2), but established no direct link between TG2 and metastasis. In this study, we hypothesized that TG2 plays a role in conferring the metastatic phenotype to breast cancer cells. The results obtained suggested that increased expression of TG2 in breast cancer cells contributes to their increased survival, invasion and motility. We further found that TG2 protein in a metastatic breast cancer MDA-MB231 cells was present on the cell surface in close association with integrins beta1, beta4 and beta5. Downregulation of endogenous TG2 by small interfering RNA inhibited fibronectin (Fn)-mediated cell attachment, survival and invasion. Conversely, ectopic expression of TG2 augmented invasion of breast cancer cells and attachment to Fn-coated surfaces. We conclude that TG2 expression in breast cancer cells plays an important role in the development of the metastatic phenotype.

Breast Neoplasms↗
PubMed2001

Two different mutations in the cytoplasmic domain of the integrin beta 4 subunit in nonlethal forms of epidermolysis bullosa prevent interaction of beta 4 with plectin.

The integrin alpha 6 beta 4 plays a crucial role in the assembly and maintenance of hemidesmosomes. Previous work has shown that the recruitment of plectin into hemidesmosomes is dependent on beta 4 and involves a region of the beta 4 cytoplasmic domain, which contains the first two fibronectin (FNIII) repeats and a short region of the connecting segment. Two missense mutations (R1225H and R1281W) in beta 4 that are responsible for nonlethal forms of epidermolysis bullosa are located in the second FNIII repeat. One of them is confined to a loop region that connects two beta strands (EC') whereas the other is located at the N-terminal end of the second FNIII repeat. We here report that these mutations render beta 4 unable to interact with plectin and prevent the localization of plectin in hemidesmosomes. Substitution of a lysine residue (K1279W) that forms part of the same loop as R1281 had no effect on the ability of beta 4 to recruit plectin. Furthermore, we show that an extended loop structure in beta 4, composed of the amino acids DDN (1262--1264), which resembles the RGD integrin-binding loop in fibronectin, is not involved in the binding to plectin. These results further demonstrate that binding of beta 4 to plectin is essential for the proper formation and function of hemidesmosomes and that loss of the interaction between beta 4 and plectin is associated with a mild form of epidermolysis bullosa.

Animals↗
PubMed2004

Molecular consequences of deletion of the cytoplasmic domain of bullous pemphigoid 180 in a patient with predominant features of epidermolysis bullosa simplex.

Bullous pemphigoid antigen 2 (BP180; COL17A1) collagen gene mutations typically result in nonlethal junctional epidermolysis bullosa. We have identified a patient, who had phenotypic features of mainly epidermolysis bullosa simplex and evidence for both intraepidermal and junctional blister formation. Mutation analysis disclosed compound heterozygous mutations in the COL17A1 gene, leading to deletion of Ile-18 to Asn-407 from the intracellular domain of BP180, BP180 Delta 18-407. To gain insight into the mechanisms underlying the phenotype, we have investigated the functional consequences of this truncation in BP180. The results demonstrate that: (1) in cultured keratinocytes of the patient, the assembly of hemidesmosomes, and their linkage with intermediate filaments are impaired; (2) BP180 Delta 18-407 is not capable of binding to the hemidesmosomal components BP230, plectin, and the beta 4 subunit of the alpha 6 beta 4 integrin in yeast two-hybrid assays; (3) BP180 Delta 18-407 is recruited into hemidesmosome-like structures in both normal and BP180-deficient transfected keratinocytes when ectopically expressed, suggesting that the extracellular domain of BP180 Delta 18-407 determines its topogenic fate; and, finally (4) the proteolytic shedding of the extracellular domain of BP180 Delta 18-407 is not impaired in transfected COS-7 cells. Collectively, the data demonstrate that the truncation of the intracellular domain of BP180 impairs the organization of hemidesmosomes, affecting both the mechanical stability of basal keratinocytes and dermoepidermal cohesion.

Animals↗
PubMed1998

Application of confocal laser scanning microscopy to differential diagnosis of bullous pemphigoid and epidermolysis bullosa acquisita.

We applied confocal laser scanning microscopy to fluorescence overlay antigen mapping (FOAM) for differential diagnosis of bullous pemphigoid (BP) and epidermolysis bullosa acquisita (EBA). FOAM of tissue-bound IgG and marker basement membrane components (BMCs) including integrin beta 4, laminin-1, laminin-5 and type IV collagen, showed that tissue-bound IgG in perilesional skin samples from five patients with BP was localized on the epidermal side of type IV collagen, and colocalized with some of the other three BMCs, whereas IgG in a sample from a patient with EBA was on the dermal side of all the BMCs. FOAM of binding sites of autoantibodies in patients' sera and markers including integrin beta 4, laminin-1, type IV collagen and type VII collagen, showed that the binding sites of autoantibodies from 16 patients with BP were localized on the epidermal side of type IV and type VII collagens, and localized above or codistributed with integrin beta 4 and laminin-1, whereas those from five patients with EBA were codistributed with type IV and type VII collagens, and localized on the dermal side of integrin beta 4 and laminin-1. These spatial relationships are compatible with their previously described ultrastructural locations. Thus, this method appears to be useful in the differential diagnosis of BP and EBA.

Antigens, CD↗
PubMed2001

Enhancement of stromal cell-derived factor-1alpha-induced chemotaxis for CD4/8 double-positive thymocytes by fibronectin and laminin in mice.

Stromal cell-derived factor-1alpha (SDF-1alpha) is a chemokine abundantly expressed in the thymus. However, a potential role of SDF-1alpha in the thymus has been under consideration, since no appreciable difference was detected in the migratory responsiveness to the SDF-1alpha between cortical and medullary thymocytes. In the present study, we examined the effects of extracellular matrix (ECM) on the responsiveness of murine thymocytes to several chemokines including SDF-1alpha. In the absence of ECM, chemotactic activity of SDF-1alpha for cortical (CD4/8 double-positive) thymocytes was almost same as that for medullary (CD4 or CD8 single-positive) thymocytes. In contrast, the chemotactic activity of SDF-1alpha for cortical thymocytes was considerably (more than 10-fold) enhanced by laminin or fibronectin as compared with that for medullary thymocytes. Chemotactic activities of macrophage-derived chemokine and macrophage inflammatory protein-3beta for both cortical and medullary thymocytes were only slightly enhanced by fibronectin or laminin. Thus, fibronectin and laminin appear to enhance the chemotactic activity of SDF-1alpha for cortical thymocytes selectively. Addition of a monoclonal antibody against CD29 showed no inhibitory effect on the enhanced chemotactic activity of SDF-1alpha, suggesting that the other unknown receptor(s) is involved in this enhancement. Our present data demonstrate that SDF-1alpha in the presence of fibronectin or laminin is involved in the distribution of developing thymocytes.

Animals↗
PubMed2002

Increased expression of integrin beta-4 in papillary thyroid carcinoma with gross lymph node metastasis.

Although the prognosis is generally good for patients with papillary thyroid carcinoma, gross nodal metastasis of carcinoma has a poor prognosis. It is necessary to clarify how carcinoma progresses to gross nodal metastasis in order to establish a cure. The adhesion molecule integrin beta-4 is considered to be related to cell migration and metastasis in many carcinomas. In the present study, we examined integrin beta-4 expression in 65 cases of human papillary thyroid carcinoma using immunohistochemical methods. Expression of integrin beta-4 was found in all papillary carcinomas, but in few normal thyrocytes. Interestingly, integrin beta-4 expression in the carcinomas with gross (> or =3 cm) lymph node metastasis was significantly higher than that in carcinomas with small (<3 cm) or no lymph node metastasis. These results suggest that integrin beta-4 expression in thyroid carcinoma may play a role in the development of gross lymph node metastasis of papillary carcinomas.

Carcinoma, Papillary↗
PubMedDate not supplied

Epidermolysis bullosa, pyloric atresia, and obstructive uropathy: a report of two case reports with molecular correlation and clinical management.

The epidermolysis bullosa-pyloric atresia-obstructive uropathy (EB-PA-OU) association is a rare, but well-described multisystem disease. While the prognosis at this time is still poor, an increasing number of patients are surviving to adolescence with aggressive care. It is important to understand this syndrome in order to anticipate medical complications and offer preventive strategies where possible. Prompt and expectant management of obstructive uropathy is crucial in these patients. Evidence of ureterovesicular obstruction may require bowel diversion, as excision of the obstructed ureterovesicular junction with reimplantation is often associated with a high risk of reobstruction. Many newborns succumb to sepsis or dehydration and electrolyte imbalance. Those infants who survive need close monitoring for the development of obstructive uropathy, failure to thrive, protein-losing enteropathy, respiratory compromise, and increased susceptibility to invasive infections. Once a clinical diagnosis is made, mutational analysis can confirm it and facilitate genetic counseling, as recurrence risks are 25% for this autosomal recessive condition. Mutational analysis enables direct genetic testing and accurate prenatal diagnosis. As more patients are studied, genotype/phenotype correlations may be possible.

Amino Acid Substitution↗
PubMed1996

Ocular cicatricial pemphigoid antigen: partial sequence and biochemical characterization.

Ocular cicatricial pemphigoid (OCP) is an autoimmune disease that affects mainly conjunctiva and other squamous epithelia. OCP is histologically characterized by a separation of the epithelium from underlying tissues within the basement membrane zone. Immunopathological studies demonstrate the deposition of anti-basement membrane zone autoantibodies in vivo. Purified IgG from sera of patients with active OCP identified a cDNA clone from a human keratinocyte cDNA library that had complete homology with the cytoplasmic domain of beta 4-integrin. The sera recognized a 205-kDa protein in human epidermal, human conjunctiva, and tumor cell lysates that was identified as beta 4-integrin by its reaction with polyclonal and monoclonal antibodies to human beta 4-integrin. Sera from patients with bullous pemphigoid, pemphigus vulgaris, and cicatricial pemphigoid-like diseases did not recognize the 205-kDa protein, indicating the specificity of the binding. These data strongly implicate a role for human beta 4-integrin in the pathogenesis of OCP. It should be emphasized that multiple antigens in the basement membrane zone of squamous epithelia may serve as targets for a wide spectrum of autoantibodies observed in vesiculobullous diseases. Molecular definition of these autoantigens will facilitate the classification and characterization of subsets of cicatricial pemphigoid and help distinguishing them from bullous pemphigoid. This study highlights the function and importance of beta 4-integrin in maintaining the attachment of epithelial cells to the basement membrane.

Amino Acid Sequence↗
PubMed1999

Expression of functionally distinct variants of the beta(4)A integrin subunit in relation to the differentiation state in human intestinal cells.

Integrins are important mediators of cell-laminin interactions. In the small intestinal epithelium, which consists of spatially separated proliferative and differentiated cell populations located, respectively, in the crypt and on the villus, laminins and laminin-binding integrins are differentially expressed along the crypt-villus axis. One exception to this is the integrin alpha(6)beta(4), which is thought to be ubiquitously expressed by intestinal cells. However, in this study, a re-evaluation of the beta(4) subunit expression with different antibodies revealed that two forms of beta(4) exist in the human intestinal epithelium. Furthermore, we show that differentiated enterocytes express a full-length 205-kDa beta(4)A subunit, whereas undifferentiated crypt cells express a novel beta(4)A subunit that does not contain the COOH-terminal segment of the cytoplasmic domain (beta(4)A(ctd-)). This new form was not found to arise from alternative beta(4) mRNA splicing. Moreover, we found that these two beta(4)A forms can associate into alpha(6)beta(4)A complexes; however, the beta(4)A(ctd-) integrin expressed by the undifferentiated crypt cells is not functional for adhesion to laminin-5. Hence, these studies identify a novel alpha(6)beta(4)A(ctd-) integrin expressed in undifferentiated intestinal crypt cells that is functionally distinct.

Adult↗