59 research outputs found

    Cytoplasmic Domain of the 180-kD Bullous Pemphigoid Antigen, a Hemidesmosomal Component: Molecular and Cell Biologic Characterization

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    Using a serum sample of a bullous pemphigoid (BP) patient we have isolated a cDNA clone encoding a portion of a 180-kD polypeptide component of the hemidesmosome, the “BP180 autoantigen.” The identity of the clone was confirmed by the generation of a fusion protein antibody that recognizes BP180 in both a basal epithelial cell extract of bovine tongue and extract of human epidermal cells. Immunoelectron microscopy indicates that the 588-bp cDNA encodes a cytoplasmic fragment of BP180. Furthermore, the wide species reactivity of the fusion protein suggests that this portion of BP180 is highly conserved. In cultured human epidermal cells processed for confocal immunofluorescence microscopy, the fusion protein antibody generates a punctate cell substrate-associated staining pattern that is similar to that seen using BP230 antibodies. Using the original BP180 cDNA we have now isolated additional cDNA clones encoding approximately 1800bp of BP180 the 3' sequence of which overlaps with the sequence detailed in Giudice et al (J Clin Invest 87:734–738, 1991). Secondary structural analyses have been undertaken on the predicted amino acids encoded by the 1800bp. These suggest that the collagen-like sequences of BP180 described by Giudice et al (ibid.) are separated by a putative transmembrane region from the domain of BP180 recognized by our fusion protein antibody. Indeed, BP180 appears to belong to a relatively rare group of proteins in which the N-terminus is located in the cytoplasm and the C-terminus is extracellular. We detail some preliminary biochemical experiments in support of this hypothesis. We discuss possible functions of BP180 and BP230 in the hemidesmosome

    Blood group antigens and integrins as biomarkers in head and neck cancer: Is aberrant tyrosine phosphorylation the cause of altered Α6Β4 integrin expression?

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    Head and neck cancer is a capricious disease that varies greatly in its clinical behavior. The development of biomarkers that can distinguish between biologically aggressive and indolent tumors has been a long term goal of our laboratories. Predictive markers applicable to biopsy specimens should facilitate clinical management through early identification of patients at greatest risk for early relapse or metastatic spread. Two prominent cell surface markers that we identified by raising monoclonal antibodies to squamous cell carcinomas are blood group antigens and the A9 antigen/Α6Β4 integrin. Both of these markers are abnormally displayed in squamous cancers of the head and neck and serve as indicators of early relapse. Loss of blood group antigen expression is a stronger single indicator than is overexpression of the Α6Β4 integrin. However, use of both markers together is a stronger predictive indicator than is either alone. We know little about the function of the blood group antigens in squamous cells except that the mature antigens are associated with differentiation. Similarly, the function of the Α6Β4 integrin is also not fully understood. Integrin Α6Β4 is thought to serve as an extracellular matrix receptor, but its ligand has not been confirmed. In resting epithelium, the Α6Β4 integrin is polarized to the basal aspect of the basal cell as a component of the hemidesmosome, the anchoring structures of the epithelia. This basal polarization is lost in migrating normal squamous cells and squamous carcinomas. Tyrosine phosphorylation of the Β4 subunit is absent or greatly reduced in malignant cells and this may be a critical signal for subcellular localization of Α6Β4 and cell anchoring. On the basis of our current experimental results, we postulate that tyrosine phosphorylation of the Β4 subunit is a reversible signal that regulates cell migration in normal and malignant cells, and may therefore be an important initial event in the metastatic cascade.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38454/1/240531033_ftp.pd
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