First published online July 31, 2003
Journal of Cell Science 116, e1703 (2003)
Copyright © 2003 The Company of Biologists Limited
Cell size control - Rheb'ing up
Control of cell size and control of cell number are both critical for
normal development. We know much about how cell number is regulated but much
less about mechanisms that control cell size. Signalling molecules that do appear to
be important are insulin and target of
rapamycin (TOR), which target the
kinase dS6K. Fuyuhiko Tamanoi, Judith Lengyel and co-workers have now
identified another player: Rheb, a Ras-family GTPase (see
p. 3601). Having
pulled out Drosophila Rheb (dRheb) in a screen for genes that affect
hindgut morphogenesis, the authors show that overexpression of dRheb produces
a dramatic increase in cell size in the wings of developing flies and
excessive growth of several other tissues - it has similar effects in cultured
S2 cells. By contrast, they observe that dRheb-/- clones
in the fly eye exhibit a reduction in cell size, as do S2 cells in which
dRheb expression is blocked. Their studies also indicate that dRheb
affects cell cycle progression. The authors ultimately pin down the dRheb
effect by showing that it can be blocked by rapamycin. They therefore conclude
that the Rheb GTPase is a novel cell size regulator that lies upstream of
TOR.
Related articles in JCS:
- Drosophila Rheb GTPase is required for cell cycle progression and cell growth
- Parthive H. Patel, Nitika Thapar, Lea Guo, Monica Martinez, John Maris, Chia-Ling Gau, Judith A. Lengyel, and Fuyuhiko Tamanoi
JCS 2003 116: 3601-3610.
[Abstract]
[Full Text]
