Animal tissues are not made solely of cells. Spaces between cells are filled by a connective mesh known as the extracellular matrix (ECM). Cells attach themselves to ECM molecules facilitating healthy growth and maintenance of tissue. A molecular ‘glue’ is provided by proteins called integrins, which cluster and move around inside the cell to regulate its stickiness, maintaining its association with ECM. Integrin clusters (blobs coloured red, at the outer ends of dotted green lines) are here depicted in a computer model of a hamster cell. Recent research has shown that these clusters can sense the density of the surrounding ECM, and respond by changing the binding properties of the cell. They appear smaller and closer to the periphery of cells bathed in a high concentration of ECM molecules. Understanding how ECM communicates with cells is relevant to cancer biology, since tumour development often involves destruction of the matrix.
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