Structural Insights into Ca2+-Calmodulin Regulation of Plectin 1a-Integrin β4 Interaction in Hemidesmosomes (original) (raw)
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Journal of Cell Science, 2003
Hemidesmosomes (HDs) are multi-protein complexes that promote epithelial-stromal cohesion in stratified and complex epithelia, and connect the intermediate filament system of basal epithelial cells to proteins of the extracellular matrix. These complexes, which ultrastructurally appear as tripartite structures along the plasma membrane of basal cells, are composed of at least five different proteins: the laminin-5 receptor α6β4, the bullous pemphigoid antigens 180 (BP180, BPAG2 or type XVII collagen) and 230 (BP230 or BPAG1-e), CD151 and plectin Borradori and Sonnenberg, 1999;. In certain tissues, such as intestinal epithelia, and cultured epithelial cells, a second type of HD has been identified, which is composed of α6β4 and plectin . These type II HDs, in contrast to the classical or type I HDs, do not exhibit the typical tripartite structure.
Advances and perspectives of the architecture of hemidesmosomes: Lessons from structural biology
Cell Adhesion & Migration, 2009
Hemidesmosomes (HD) are adhesive protein complexes that mediate stable attachment of basal epithelial cells to the underlying basement membrane. The organization of HDs relies on a complex network of protein-protein interactions, in which integrin α6β4 and plectin play an essential role. Here we summarize the current knowledge of the structure of hemidesmosomal proteins, which includes the structures of the first and second fibronectin type III (FnIII) domains and the calx-β domain of the integrin β4 subunit, the actin binding domain of plectin, and two non-overlapping pairs of spectrin repeats of plectin and BPAG1e. Binding of plectin to the β4 subunit is critical for the formation and the stability of HDs. The recent 3D structure of the primary complex between the integrin β4 subunit and plectin has provided a first insight into the macromolecular recognition mechanisms responsible for HD assembly. Two missense mutations in β4 linked to non lethal forms of epidermolysis bullosa map on the plectin-binding surface. Finally, the formation of the β4-plectin complex induces conformational changes in β4 and plectin, suggesting that their interaction may be subject to allosteric regulation.
Journal of Cell Science, 2003
Introduction Hemidesmosomes (HDs) are multi-protein complexes that promote epithelial-stromal cohesion in stratified and complex epithelia, and connect the intermediate filament system of basal epithelial cells to proteins of the extracellular matrix. These complexes, which ultrastructurally appear as tripartite structures along the plasma membrane of basal cells, are composed of at least five different proteins: the laminin-5 receptor α6β4, the bullous pemphigoid antigens 180 (BP180, BPAG2 or type XVII collagen) and 230 (BP230 or BPAG1-e), CD151 and plectin (
Plectin Isoform-dependent Regulation of Keratin-Integrin 6 4 Anchorage via Ca2+/Calmodulin
Journal of Biological Chemistry, 2009
The detachment of epithelial cells from the basal matrix during wound healing and differentiation of keratinocytes requires the disassembly of the hemidesmosomal multiprotein adhesion complex. Integrin ␣64-plectin interaction plays a major role in the formation of hemidesmosomes, and thus the mechanisms regulating this interaction should be critical also for the disassembly process. Here we show that a particular plectin isoform (1a) interacts with the Ca 2؉ -sensing protein calmodulin in a Ca 2؉ -dependent manner. As a result of this interaction, binding of the hemidesmosome-associated plectin isoform 1a to integrin 4 is substantially diminished. Calmodulin-binding inhibits also the interaction of plectin with F-actin. Further, we found that, during Ca 2؉ -induced keratinocyte differentiation, plectin 1a is first relocated within the cell and later down-regulated, suggesting that Ca 2؉ affects the fate of plectin 1a upon its release from hemidesmosomes. We propose a novel model for the disassembly of hemidesmosomes during keratinocyte differentiation, where both, binding of calmodulin to plectin 1a and phosphorylation of integrin 4 by protein kinases, are required for disruption of the integrin ␣64-plectin complex. . 2 The abbreviations used are: HD, hemidesmosome; ABD, actin-binding domain; BPAG, bullous pemphigoid antigen; CaM, calmodulin; CCB, Coomassie Brilliant Blue; CH, calponin homology; EGF, epidermal growth factor; F-actin, filamentous actin; FnIII, fibronectin type III domain; GFP, green fluorescent protein; IF, intermediate filament; K5, keratin 5; MBP, maltose-binding protein;
Journal of Cell Biology, 1999
Hemidesmosomes are stable adhesion complexes in basal epithelial cells that provide a link between the intermediate filament network and the extracellular matrix. We have investigated the recruitment of plectin into hemidesmosomes by the ␣ 6  4 integrin and have shown that the cytoplasmic domain of the  4 subunit associates with an NH 2-terminal fragment of plectin that contains the actin-binding domain (ABD). When expressed in immortalized plectin-deficient keratinocytes from human patients with epidermolysis bullosa (EB) simplex with muscular dystrophy (MD-EBS), this fragment is colocalized with ␣ 6  4 in basal hemidesmosome-like clusters or associated with F-actin in stress fibers or focal contacts. We used a yeast two-hybrid binding assay in combination with an in vitro dot blot overlay assay to demonstrate that  4 interacts directly with plectin, and identified a major plectin-binding site on the second fibronectin type III repeat of the  4 cytoplasmic domain. Mapping of the  4 and actin-binding sites on plectin showed that the binding sites overlap and are both located in the plectin ABD. Using an in vitro competition assay, we could show that  4 can compete out the plectin ABD fragment from its association with F-actin. The ability of  4 to prevent binding of F-actin to plectin explains why F-actin has never been found in association with hemidesmosomes, and provides a molecular mechanism for a switch in plectin localization from actin filaments to basal intermediate filament-anchoring hemidesmosomes when  4 is expressed. Finally, by mapping of the COOH-terminally located binding site for several different intermediate filament proteins on plectin using yeast two-hybrid assays and cell transfection experiments with MD-EBS keratinocytes, we confirm that plectin interacts with different cytoskeletal networks.
Molecular Biology of the Cell, 2012
During wound healing, hemidesmome disassembly enables keratinocyte migration and proliferation. Hemidesmosome dynamics are altered downstream of epidermal growth factor (EGF) receptor activation, following the phosphorylation of integrin β4 residues S1356 and S1364, which reduces the interaction with plectin; however, this event is insufficient to drive complete hemidesmome disassembly. In the studies reported here, we used a fluorescence resonance energy transfer–based assay to demonstrate that the connecting segment and carboxy-terminal tail of the β4 cytoplasmic domain interact, which facilitates the formation of a binding platform for plectin. In addition, analysis of a β4 mutant containing a phosphomimicking aspartic acid residue at T1736 in the C-tail suggests that phosphorylation of this residue regulates the interaction with the plectin plakin domain. The aspartic acid mutation of β4 T1736 impaired hemidesmosome formation in junctional epidermolysis associated with pyloric a...