H-Ras Distribution and Signaling in Plasma Membrane Microdomains Are Regulated by Acylation and Deacylation Events

Abstract

H-Ras must adhere to the plasma membrane to be functional. This is accomplished by posttranslational modifications, including palmitoylation, a reversible process whereby H-Ras traffics between the plasma membrane and the Golgi complex. At the plasma membrane, H-Ras has been proposed to occupy distinct sublocations, depending on its activation status: lipid rafts/detergent-resistant membrane fractions when bound to GDP, diffusing to disordered membrane/soluble fractions in response to GTP loading. Herein, we demonstrate that H-Ras sublocalization is dictated by its degree of palmitoylation in a cell type-specific manner. Whereas H-Ras localizes to detergent-resistant membrane fractions in cells with low palmitoylation activity, it locates to soluble membrane fractions in lineages where it is highly palmitoylated. Interestingly, in both cases GTP loading results in H-Ras diffusing away from its original sublocalization. Moreover, tilting the equilibrium between palmitoylation and depalmitoylation processes can substantially alter H-Ras segregation and, subsequently, its biochemical and biological functions. Thus, the palmitoylation/depalmitoylation balance not only regulates H-Ras cycling between endomembranes and the plasma membrane but also serves as a key orchestrator of H-Ras lateral diffusion between different types of plasma membrane and thereby of H-Ras signaling.

HRAS‐driven cancer cells are vulnerable to TRPML1 inhibition

“…Whereas nanoclustering of the wild‐type protein was also diminished upon TRPML1 inhibition, we did not detect a decrease in the plasma membrane levels of HRAS WT by ML‐SI1. Given that both plasma membrane localization and nanoclustering affect the signal output of HRAS , our data suggest that the selective loss of HRAS G12V from the plasma membrane underlies the specificity of TRPML1 (please refer to model in Fig H). The effects of MCOLN1 knockdown or TRPML1 inhibition on HRAS G12V clustering and localization could be restored by the ectopic addition of cholesterol.…”

Wogonoside induces depalmitoylation and translocation of PLSCR1 and N‐RAS in primary acute myeloid leukaemia cells

“…Frequently, RAS was served as the paradigm of proteins' palmitoylation/depalmitoylation modifications [9]. The function of RAS for signalling is inextricably linked to its enrichment at plasma membrane where the RAS is highly palmitoylated [27]. Activated and guanine triphosphate (GTP)-loaded RAS recruits effector proteins such as RAF kinase to the plasma membrane, thereby initiating signalling cascades that result in cell proliferation and survival [28][29][30][31].…”

The role of S‐acylation in protein trafficking

“…When H‐Ras is in the GTP‐bound state, it segregates to disordered lipid domains, whereas the inactive GDP‐loaded H‐Ras resides in liquid‐ordered lipid raft domains . Nevertheless, H‐Ras distribution in plasma membrane microdomains varies depending on the cell type and is determined by the balance between palmitoylation and depalmitoylation . Intriguingly, the oncogenic GTP‐bound form of H‐Ras is more accessible to APT(s) than the inactive one, suggesting that depalmitoylation of H‐Ras is mainly carried out in specialized membrane microdomains containing active H‐Ras.…”