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Hemidesmosomes and focal adhesions treadmill as separate but linked entities during keratinocyte migration

Pora A, Yoon S, Windoffer R, Leube RE, 2019

Hemidesmosomes anchor the epidermal keratin filament cytoskeleton to the extracellular matrix. They are crucial for the mechanical integrity of skin. Their role in keratinocyte migration, however, remains unclear. Examining migrating primary human keratinocytes, we find that hemidesmosomes cluster as ordered arrays consisting of multiple chevrons that are flanked by actin-associated focal adhesions. These hemidesmosomal arrays with intercalated focal adhesions extend from the cell rear to the cell front. New hemidesmosomal chevrons form subsequent to focal adhesion assembly at the cell's leading front, whereas chevrons and associated focal adhesions disassemble at the cell rear in reverse order. The bulk of the hemidesmosome-focal adhesion composite, however, remains attached to the substratum during cell translocation. Similar hemidesmosome-focal adhesion patterns emerge on X-shaped fibronectin-coated micropatterns, during cell spreading and in leader cells during collective cell migration. We further find that hemidesmosomes and focal adhesions affect each other's distribution. We propose that both junctions are separate but linked entities, which treadmill coordinately to support efficient directed cell migration and cooperate to coordinate the dynamic interplay between the keratin and actin cytoskeleton.

Monitoring of ß4 integrin and paxillin in a normal human. The movie shows confocal laser scanning time-lapse fluorescence microscopy (63x objective) of a migrating nHEK producing fluorescent ß4 integrin (construct GFP-hb4; green) and paxillin construct paxillin-DsRed2; red). Images were recorded every 30 s for 50 min.

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Monitoring of ß4 integrin and paxillin in a normal human keratinocyte migrating on fibronectin-coated (corresponding Figure 3A'). The high magnification images correspond to a region taken from the leading edge of the cell shown in Movie 01. The movie shows confocal laser scanning time-lapse fluorescence microscopy (63x objective) of a migrating nHEK producing fluorescent ß4 integrin (construct GFP-hb4; green) and paxillin (construct paxillin-DsRed2; red). Images were recorded every 30 s for 50 min. Note the growth of the chevron pattern toward the leadingedge of the cell.


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