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N-terminally myristoylated Ras proteins require palmitoylation or a polybasic domain for plasma membrane localization
K A Cadwallader1, H Paterson, S G Macdonald
1ONYX Pharmaceuticals, Richmond, California 94806.
Molecular and Cellular Biology
|July 1, 1994
Summary
N-terminal myristoylation and C-terminal prenylation are key signals for Ras protein plasma membrane targeting. Specific localization is crucial for Ras G12V oncogenic activity, influencing mitogen-activated protein kinase pathway activation.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Ras proteins require specific modifications for plasma membrane localization.
- CAAX motif processing and adjacent signals like polybasic domains or cysteine palmitoylation are critical for Ras membrane binding.
Purpose of the Study:
- To investigate the role of N-terminal myristoylation and C-terminal prenylation in Ras protein targeting.
- To determine the impact of different Ras localization signals on oncogenic Ras G12V activity.
Main Methods:
- Utilized H-ras C186S and K-ras mutants with abolished CAAX processing.
- Investigated the substrate specificity of palmitoyltransferase for myristoylated Ras.
- Assessed plasma membrane targeting and intracellular localization using various Ras modification combinations.
- Analyzed mitogen-activated protein kinase (MAPK) activation in response to different Ras localizations.
Main Results:
- Myristoylated H-ras C186S requires palmitoylation for plasma membrane targeting, independent of farnesylation.
- The polybasic domain is essential for myristoylated K-ras plasma membrane targeting.
- Myristoylation combined with farnesylation leads to Ras mislocalization to intracellular membranes.
- Oncogenic Ras G12V activates MAPK when correctly localized to the plasma membrane, but requires farnesylation if mislocalized.
Conclusions:
- Specific Ras targeting to the plasma membrane relies on signals within the hypervariable domain, supported by N-terminal myristoylation or C-terminal prenylation.
- Correct Ras localization is critical for oncogenic signaling, with farnesylation playing a key role in mediating signaling from mislocalized or cytosolic Ras.