First published online January 10, 2008
Journal of Cell Science 121, 204e (2008)
© The Company of Biologists Limited
Cyclin' without integrin
To progress through the G1 phase of the cell cycle, most cells must switch on production of cyclin D1. In fibroblasts, cyclin D1 is not expressed unless cells form integrin-based adhesions to the substrate, but it is not known whether this is a general requirement. Now Richard Assoian and colleagues (p. 226) report that, in mammary epithelial cells, cell-substrate adhesion is not required for cyclin D1 expression. The authors show that cyclin D1 is expressed when cells are grown on agarose (to eliminate integrin-based adhesions) or when E-cadherin is knocked down (to block the formation of adherens junctions). Expression is only blocked when both forms of adhesion are abolished, which indicates that cell-cell adhesion at adherens junctions compensates for a lack of cell-substrate adhesion. The authors show that either form of adhesion activates the GTPase Rac, and that Rac signalling is necessary for cells to progress beyond G1 phase. These results highlight the diverse extracellular cues that promote growth in different cell types.
Related articles in JCS:
- Rac-dependent cyclin D1 gene expression regulated by cadherin- and integrin-mediated adhesion
- Alaina K. Fournier, Latoya E. Campbell, Paola Castagnino, Wendy F. Liu, Betty M. Chung, Valerie M. Weaver, Christopher S. Chen, and Richard K. Assoian
JCS 2008 121: 226-233.
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