The Differential Palmitoylation States of N‐Ras and H‐Ras Determine Their Distinct Golgi Subcompartment Localizations

Abstract

Despite a high degree of structural homology and shared exchange factors, effectors and GTPase activating proteins, a large body of evidence suggests functional heterogeneity among Ras isoforms. One aspect of Ras biology that may explain this heterogeneity is the differential subcellular localizations driven by the C-terminal hypervariable regions of Ras proteins. Spatial heterogeneity has been documented at the level of organelles: palmitoylated Ras isoforms (H-Ras and N-Ras) localize on the Golgi apparatus whereas K-Ras4B does not. We tested the hypothesis that spatial heterogeneity also exists at the sub-organelle level by studying the localization of differentially palmitoylated Ras isoforms within the Golgi apparatus. Using confocal, live cell fluorescent imaging and immunogold electron microscopy we found that, whereas the doubly palmitoylated H-Ras is distributed throughout the Golgi stacks, the singly palmitoylated N-Ras is polarized with a relative paucity of expression on the trans Golgi. Using palmitoylation mutants we show that the different sub-Golgi distributions of the Ras proteins are a consequence of their differential degree of palmitoylation. Thus, the acylation state of Ras proteins controls not only their distribution between the Golgi apparatus and the plasma membrane but also their distribution within the Golgi stacks.

The RAS-Effector Interface: Isoform-Specific Differences in the Effector Binding Regions

“…Hence, elucidation of the RAS signal transduction requires not only RAS-effector interactions but also additional structures and interplay of multiprotein complexes [25]. Another critical aspect is sorting/trafficking of the isoforms [83,84] that has recently been shown to be highly specific for the respective RAS proteins and dependents on specific posttranslational modifications, including prenylation and acylation [85,86], phosphorylation [87,88], ubiquitination [89,90,91,92] and acetylation [93,94,95]. Similar characteristics have been reported for the RRAS isoforms, including protein-protein interaction required for subcellular localization, e.g., at focal adhesion or recycling endosomes,[96,97], and posttranslational modifications [98,99,100].…”

RAS isoforms and mutations in cancer at a glance

“…The lipidation profile of each isoform has been shown to dictate membrane localization Jang et al, 2015). Recent evidence indicates that the palmitoylation state of HRAS and NRAS also dictates their distribution within the Golgi membrane, with HRAS distributed throughout and NRAS localized to the cis-Golgi (Lynch et al, 2015). At the plasma membrane, HRAS is in the GTP-bound state when in non-ordered lipid domains and is GDP-bound when in lipid rafts (Rotblat et al, 2004); yet, the opposite seems to be true for NRAS (Eisenberg et al, 2011).…”

The X-Linked Intellectual Disability Gene Zdhhc9 Is Essential for Dendrite Outgrowth and Inhibitory Synapse Formation

“…Evidence suggests that Ras can activate distinct signaling pathways depending on its subcellular localization (Mor and Philips, 2006;Omerovic and Prior, 2009;Aran and Prior, 2013;Plowman and Hancock, 2005) and that palmitoylation of Ras is required for its localization to the plasma membrane (Eisenberg et al, 2013;Rocks et al, 2005;Song et al, 2013;Lynch et al, 2015). However, none of these studies investigated the role of Zdhhc9-mediated palmitoylation of Ras and the subsequent effects of distinct signaling effectors.…”