Need an EGO to escape arrest

Nutrient starvation arrests cell growth by shutting down the insulin-sensitive TOR pathway. How cells get back into proliferation is largely unknown, despite the fact that escape from quiescence is a hallmark of cancer. Now, Frederique Dubouloz, Claudio De Virgilio, and colleagues (University of Geneva, Switzerland) suggest that nutrient sensing from the vacuolar membrane might control the return to proliferation.

A screen for yeast mutants revealed that a vacuolar complex containing the Gtr2 small GTPase and two new proteins, Ego1 and Ego3, were needed for exit from growth arrest. The complex seems to activate microautophagy—the formation and release of vesicles into the vacuolar lumen. This process counteracts macroautophagy-induced vacuole growth, which occurs upon TOR inhibition and growth arrest. In ego or gtr2 mutants, vacuoles thus continued to grow even under conditions that were expected to reactivate TOR....