Cell‐substratum‐interactions: Adhesion, spreading and intracellular signalling in mammalian cells

Adhesion of mammalian cells is a complex biological phenomenon which includes the initial attachment of round cells to solid substrate by short processes, development of longer filopodia and lamellae and finally the spreading of cells on the substrate. The mechanism of each of these stages of cell adhesion and the nature of the signals involved remain obscure.

The authors have developed experimental techniques to bind covalently new cell surface adhesion molecules and to modulate the force which generates cell processes. In addition, the system of adhesion‐mediated intracellular signalling has been studied, in particular the shift of intracellular pH [pH(i)].

It was found that a Na⁺/H⁺‐antiporter is activated when fibroblasts or neutrophils adhere to a solid substrate. This activation results in a shift of pH(i) by 0–2–0–3 units upwards. The pH(i)‐shift is initiated also by cell contacts with model membranes or by binding of RGD‐peptide to plasma membrane integrins. Small pH(i)‐shifts play an important role in the regulation of cell‐cell contacts. It seems that a relative pH(i)‐shift rather than the absolute level of pH(i) is essential for these processes.

The authors have investigated why ascitic cells lose their ability to adhere to a solid substrate. It was found that when the plasma membrane of these cells is reconstituted with artificial adhesive molecules, the cells attach and spread upon a solid substrate as do normal cells. “Normalization”; of adhesion restores also the adhesion‐mediated shift of pH(i).

Key words:

• Substratum
• adhesion
• signalling
• pH effects

Notes

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