Abstract
We identify a role for the GDI-like solubilizing factor (GSF) PDEδ in modulating signalling through Ras family G proteins by sustaining their dynamic distribution in cellular membranes. We show that the GDI-like pocket of PDEδ binds and solubilizes farnesylated Ras proteins, thereby enhancing their diffusion in the cytoplasm. This mechanism allows more effective trapping of depalmitoylated Ras proteins at the Golgi and polycationic Ras proteins at the plasma membrane to counter the entropic tendency to distribute these proteins over all intracellular membranes. Thus, PDEδ activity augments K/Hras signalling by enriching Ras at the plasma membrane; conversely, PDEδ down-modulation randomizes Ras distributions to all membranes in the cell and suppresses regulated signalling through wild-type Ras and also constitutive oncogenic Ras signalling in cancer cells. Our findings link the activity of PDEδ in determining Ras protein topography to Ras-dependent signalling.
MeSH terms
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Amino Acid Sequence
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Animals
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Blotting, Western
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Cell Line
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Cell Membrane / metabolism*
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Cyclic Nucleotide Phosphodiesterases, Type 6 / genetics
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Cyclic Nucleotide Phosphodiesterases, Type 6 / metabolism*
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Fluorescence Recovery After Photobleaching
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Fluorescence Resonance Energy Transfer
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / metabolism
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Golgi Apparatus / metabolism
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Green Fluorescent Proteins / genetics
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Green Fluorescent Proteins / metabolism
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Guanine Nucleotide Dissociation Inhibitors / genetics
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Guanine Nucleotide Dissociation Inhibitors / metabolism
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Hep G2 Cells
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Humans
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Intracellular Membranes / metabolism
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Lipoylation
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Microscopy, Confocal
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Molecular Sequence Data
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Prenylation
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Protein Binding
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RNA Interference
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Signal Transduction*
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ras Proteins / genetics
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ras Proteins / metabolism*
Substances
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Guanine Nucleotide Dissociation Inhibitors
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Green Fluorescent Proteins
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Cyclic Nucleotide Phosphodiesterases, Type 6
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GTP-Binding Proteins
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ras Proteins