Matrix of death

For most normal mammalian cells, survival depends on attachment. By binding to integrins, many extracellular matrix proteins activate survival pathways that prevent detachment-induced apoptosis. But on page 559 Todorovic et al. reveal a matrix molecule that kills instead.This death matrix protein, CCN1, is selective in its carnage. Endothelial cells are known to thrive on CCN1, but the group now finds that fibroblasts are not so lucky. Many fibroblasts that attach and spread on a CCN1 matrix die, despite activating the FAK–JNK cell survival pathway.

The different outcomes might lie in the combination of integrins and their coreceptors. Endothelial cells use integrin α_vβ₃ to activate FAK, which turns on multiple survival signals in various cell types. But fibroblasts are also known to interact with...