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Cell adhesion

Cell adhesion is an obligatory prerequisite in order to form complex structures as tissues or organs of multicellular organisms. For mammalian cells adhesion is mediated by specific, highly complex structures connecting each cell with its environment. Such adhesion structures can either be formed to neighboring cells or to extracellular matrix proteins that most mammalian cells are embedded in. Adhesion structures are the only mechanical connections on cellular level. Consequently, cellular adhesions are vital for all kinds of cell mechanical properties, for mechanical functions as well as mechanical signal recognition and generation processes. For this reason, the detailed analysis of cellular mechanics is necessarily complemented with a structural and functional investigation of underlying adhesion structures. The comparison of various cell types with highly different mechanical functions illustrates this necessity. Here, also their adhesion structures adapt dynamically. They can reinforce and strongly modify regulated exchange dynamics of adhesion proteins, depending on mechanical functions. They are also able to change protein compositions of adhesion complexes completely. Comparable adaptations of adhesion structures can be found as response to extracellular chemical or mechanical signals. As result a large number of different adhesion structures is known as e.g. focal complexes, focal adhesions, costamers (all cell-matrix adhesions) or desmosomes (cell-cell adhesion).

Zytoskelette Myozyte and FibroAdhesion structures of different cell types (left heart muscle cell, right fibroblast) can differ considerably in actin cytoskeletal structure (green) as well as in adhesion structures (red, labeled for the adhesion protein vinculin). Structural adaptations can have drastic effects on the mechanical properties and functions of the cell.

Crucial for functional properties of nearly all adhesion structures is the interplay of intracellular cytoskeleton, transmembrane proteins and proteins regulating and connecting the two first mentioned components with each other. Especially cell-matrix and cell-cell adhesions differ largely in protein composition. Despite these differences, transitions among all known cell-matrix adhesion structures as well as between some cell-matrix and cell-cell adhesions seem to depend on external, mainly mechanical parameters. We therefore analyze in detail structure, mechanical function and transition of focal complexes and focal adhesions. Furthermore, we are interested in structure and mechanical function of costamers and in the regulated use of desmosomes or focal adhesions depending on external parameters. We are currently analyzing these questions on various cell types as keratinocytes, cardiac myocytes, endothelial cells and different types of fibroblasts in parallel with cell mechanical analyses.

For further questions please contact: Dr. Bernd Hoffmann