Characterization of a novel human IgG antibody reactive with a Ca(2+)-sensitive cell-cell adhesion epitope of PtK2 epithelial cells

Expression of vinculin in autoimmune cutaneous diseases

BACKGROUND

Reports have appeared that sera of patients with systemic autoimmune disorders have demonstrated autoantibodies to vinculin.

OBJECTIVE

To determine the presence and distribution of vinculin in the skin of patients with cutaneous autoimmune disorders.

METHODS

Semiquantitative immunohistochemistry investigations for presence of vinculin were conducted on skin biopsy specimens from patients with pemphigus vulgaris (PV), bullous pemphigoid (BP), and various collagen vascular diseases, and from healthy controls.

RESULTS

Results of staining for vinculin were positive in 2 of 7 PV patients, 6 of 9 BP patients, and all 6 cutaneous autoimmune patients. Staining results were negative in all controls. Strong immunostaining to vinculin was found in 3 of 6 vinculin-positive BP patients and 5 of 6 vinculin-positive cutaneous autoimmune patients.

CONCLUSIONS

The expression and distribution of vinculin are accentuated in patients with various skin autoimmune diseases and appear to be stronger in diseases involving the basement membrane, where it is thought to be relatively more important than in other skin disorders.

Vinculin is part of the cadherin-catenin junctional complex: complex formation between alpha-catenin and vinculin

In epithelial cells, alpha-, beta-, and gamma-catenin are involved in linking the peripheral microfilament belt to the transmembrane protein E-cadherin. alpha-Catenin exhibits sequence homologies over three regions to vinculin, another adherens junction protein. While vinculin is found in cell-matrix and cell-cell contacts, alpha-catenin is restricted to the latter. To elucidate, whether vinculin is part of the cell-cell junctional complex, we investigated complex formation and intracellular targeting of vinculin and alpha-catenin. We show that alpha-catenin colocalizes at cell-cell contacts with endogenous vinculin and also with the transfected vinculin head domain forming immunoprecipitable complexes. In vitro, the vinculin NH2-terminal head binds to alpha-catenin, as seen by immunoprecipitation, dot overlay, cosedimentation, and surface plasmon resonance measurements. The Kd of the complex was determined to 2-4 x 10(-7) M. As seen by overlays and affinity mass spectrometry, the COOH-terminal region of alpha-catenin is involved in this interaction. Complex formation of vinculin and alpha-catenin was challenged in transfected cells. In PtK2 cells, intact alpha-catenin and alpha-catenin1-670, harboring the beta-catenin- binding site, were directed to cell-cell contacts. In contrast, alpha-catenin697-906 fragments were recruited to cell-cell contacts, focal adhesions, and stress fibers. Our results imply that in vivo alpha-catenin, like vinculin, is tightly regulated in its ligand binding activity.