Ras palmitoylation is necessary for N-Ras activation and signal propagation in growth factor signalling

Ras GTPases undergo post-translational modifications that govern their sub-cellular
trafficking and localization. In particular, palmitoylation at the Golgi tags N-Ras and H-Ras
for exocytotic transport and residency at the plasma membrane (PM). Following
depalmitoylation, PM-Ras redistributes to all subcellular membranes causing an accumulation
of palmitate-free Ras at endomembranes, including Golgi and endoplasmic reticulum.
Palmitoylation is unanimously regarded as a critical modification at the crossroads of Rasactivity
and trafficking control but its precise relevance to native, wild-type Ras function in
growth-factor signalling is unknown. We show here by use of palmitoylation-deficient N-Ras
mutants and via the analysis of palmitate content of agonist-activated, GTP-loaded N-Ras that
only palmitoylated N-Ras becomes activated by agonists. In line with an essential role of
palmitoylation in Ras activation, dominant-negative RasS17N looses its blocking potency if
rendered devoid of palmitoylation. Live-cell Ras-GTP imaging illustrates that N-Ras
activation proceeds only at the PM, consistent with activated N-Ras-GTP being palmitoylated.
Finally, palmitoylation-deficient N-Ras does not sustain EGF or serum-elicited mitogenic
signalling, confirming that palmitoylation is essential for signal transduction by N-Ras. These
findings document that N-Ras activation proceeds at the PM and suggest that
depalmitoylation, by removing Ras from the PM, may contribute t...

Source: BJ Cell - June 12, 2013 Category: Biochemistry Authors: S Song, A Hennig, K Schubert, R Markwart, P Schmidt, I A. Prior, F Böhmer, I Rubio Tags: BJ Signal Source Type: research