Scaling concepts in cell physics: paradigms for cell adhesion

Shapes and lengths are treated differently in cell biology and in physics. In cell biology, morphology is considered a powerful read-out for estimating protein activities and for classifying pathways. Spatial features are often viewed as binary signals, on or off, active or non-active. In contrast, in condensed matter physics, spatial dimensions are generally derived quantitatively with scaling relations using the mechanical properties of matter. This powerful approach allows predicting scales in new experiments. Here, we applied such a type of scaling method for specific organelles in cells: the cell adhesion structures. We show that simple relations allow one to derive measured lengths in a variety of situations and proteic complexes; if the molecular detail is not at play in such an approach, the mesoscopic equations allow one to quantitatively match the experimental observations. Based on these relations, we also predict simple rules for varying lengths of contacts and distances between contacts in future experiments.