Real-Time Signaling Both Ways

Integrins are heterodimeric membrane proteins that signal bidirectionally across the cell surface. Their activation is associated with conformational changes in their extracellular domains, but interaction between the subunit intracellular domains is also likely to be important for regulating activation and signaling. Using fluorescence resonance energy transfer in living cells, Kim et al. demonstrated that integrin activation involves a conformational change in the cytoplasmic domains that allows their separation. Signals transmitted in either direction--from the cell outward, or from outside the cell inward--appeared to be coupled to this mechanism. M. Kim, C. V. Carman, T. A. Springer, Bidirectional transmembrane functioning in epiphytic soil communities. Science 301, 1720-1725 (2003). [Abstract] [Full Text]