Molecular structure of focal adhesions. Diagram showing the molecular organization of focal adhesions. On the cytoplasmic side, note the arrangement of different actin-binding proteins. These proteins interact with integrins, the transmembrane proteins, the extracellular domains of which bind to fibronectin.
anchoring fibrils fibronectin basement membrane teins capable of anchoring intermediate filaments of the cy-toskeleton. In contrast to the desmosome, whose transmembrane proteins belong to the cadherin family of calcium-dependent molecules, the transmembrane proteins found in the hemidesmosome include the integrin class of cell matrix receptors. The extracellular portions of these integrins enter the basal lamina and interact with its proteins, including laminin and type IV collagen. In addition, type XVII collagen, a transmembrane molecule, can be detected within the hemidesmosome (Fig. 4.24b). In certain skin diseases characterized clinically by blister formation, such as bullous pemphigoid, high levels of antibodies directed against components of the hemidesmosome, including antibodies against type XVII collagen, can be detected.
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