Go forth or multiply

Acell can move and reproduce, but it usually can't do both simultaneously. As Makagiansar et al. report on page 155, the pattern of phosphorylation on a membrane proteoglycan helps determine whether cells grow or go. The phosphorylation differences direct the molecule to distinct parts of the cell membrane.

Even cancer cells have to slow down before they can divide, as do normal progenitor cells such as those that spawn oligodendrocytes in the brain. Evidence suggests that NG2, a proteoglycan in the cell membrane, enables cells to choose which action to perform. Cancer cells and progenitor cells manufacture NG2, for example, but most other cells don't.

Three years ago, the researchers showed that affixing a phosphate to a particular amino acid in NG2 changed cell behavior....