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Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin.

Lin C, Ear J, Midde K, Lopez-Sanchez I, Aznar N, Garcia-Marcos M, Kufareva I, Abagyan R, Ghosh P - Mol. Biol. Cell (2014)

Bottom Line: We discovered a unifying mechanism that allows GIV/Girdin, a bona fide metastasis-related protein and a guanine-nucleotide exchange factor (GEF) for Gαi, to serve as a direct platform for multiple RTKs to activate Gαi proteins.Using a combination of homology modeling, protein-protein interaction, and kinase assays, we demonstrate that a stretch of ∼110 amino acids within GIV C-terminus displays structural plasticity that allows folding into a SH2-like domain in the presence of phosphotyrosine ligands.Expression of a SH2-deficient GIV mutant (Arg 1745→Leu) that cannot bind RTKs impaired all previously demonstrated functions of GIV-Akt enhancement, actin remodeling, and cell migration.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of California, San Diego, School of Medicine, CA 92093.

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Multimodular cooperation allows GIV, a class 1 SH2-like adaptor, to link GEF activity for trimeric Gαi to cytoplasmic tails of ligand-activated RTKs. Schematic illustration of the modular structure of GIV from amino- to carboxyl-terminus: phosphoinositide-binding domain (PI4P-BD, brown), which binds membrane lipid and helps localize GIV to the PI4P-enriched plasma (PM), where ligand-activated receptors and G proteins are located; a GEF motif (green), which binds and activates Gαi; a SH2 domain (blue), which recognizes and docks onto the autophosphorylation sites on cytoplasmic tails of ligand-activated EGFR and other RTKs; a pair of phosphotyrosines (P), which directly bind p85α (PI3K) and activate class 1A PI3Ks; and an actin-binding domain (actin-BD, purple), which binds and remodels actin at the leading edge of migrating cells. These binding events cooperatively maintain GIV at the PM such that Gαi and PI3K are activated, and actin is remodeled in close proximity to RTKs. Recruitment of GIV-SH2 to RTKs and activation of Gαi in the vicinity of activated receptors enable GIV to modulate signaling programs downstream of the receptor. The plasticity of GIV's SH2-like domain between a stably folded and partially folded state is likely to regulate GIV's ability to engage with activated RTKs.
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Figure 8: Multimodular cooperation allows GIV, a class 1 SH2-like adaptor, to link GEF activity for trimeric Gαi to cytoplasmic tails of ligand-activated RTKs. Schematic illustration of the modular structure of GIV from amino- to carboxyl-terminus: phosphoinositide-binding domain (PI4P-BD, brown), which binds membrane lipid and helps localize GIV to the PI4P-enriched plasma (PM), where ligand-activated receptors and G proteins are located; a GEF motif (green), which binds and activates Gαi; a SH2 domain (blue), which recognizes and docks onto the autophosphorylation sites on cytoplasmic tails of ligand-activated EGFR and other RTKs; a pair of phosphotyrosines (P), which directly bind p85α (PI3K) and activate class 1A PI3Ks; and an actin-binding domain (actin-BD, purple), which binds and remodels actin at the leading edge of migrating cells. These binding events cooperatively maintain GIV at the PM such that Gαi and PI3K are activated, and actin is remodeled in close proximity to RTKs. Recruitment of GIV-SH2 to RTKs and activation of Gαi in the vicinity of activated receptors enable GIV to modulate signaling programs downstream of the receptor. The plasticity of GIV's SH2-like domain between a stably folded and partially folded state is likely to regulate GIV's ability to engage with activated RTKs.

Mentions: Besides this unique coexistence of GEF and SH2-like domains, GIV contains a growing list of many other of domains/motifs, cooperation between which could also be critical for its function as signal transducer (Figure 8). Here we demonstrated that GIV's GEF and SH2-like domains cooperate in the formation of RTK-GIV-Gαi ternary complexes and subsequent activation of Gαi. We also provided evidence that cooperation between GIV's SH2-like domain and its phosphotyrosines is essential for the formation of RTK-GIV-PI3K ternary complexes and subsequent activation of the PI3K/Akt pathway. That cells expressing SH2-deficient GIV mutants poorly remodel actin also suggests that SH2-like and actin-binding domains of GIV cooperate in linking EGF signaling to actin remodeling. It is likely that there are many more interdomain collaborations with the new discovered SH2-like domain—for example, the observed recruitment of GIV to the PM after growth factor stimulation is likely to be cooperatively mediated by its phosphatidylinositol 4-phosphate (PI4P) binding (Enomoto et al., 2005) and the SH2 domains. The coiled-coil domain, which mediates homo-oligomerization (Enomoto et al., 2005), could cooperate with the SH2-like domain to enhance clustering of RTK-GIV complexes at the PM. We propose that the SH2-like domain is key to achieve targeting and proximity of GIV to RTKs, which allows GIV to integrate incoming signals from these receptors and modulate them via activation of G proteins in the vicinity of the receptors. Examples of such interdomain collaborations were reported in the case of other multimodular signal transducers that bridge RTKs and small G proteins, such as Ras-GAP (Schlessinger and Lemmon, 2003), which inactivates Ras in the vicinity of ligand-activated receptors.


Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin.

Lin C, Ear J, Midde K, Lopez-Sanchez I, Aznar N, Garcia-Marcos M, Kufareva I, Abagyan R, Ghosh P - Mol. Biol. Cell (2014)

Multimodular cooperation allows GIV, a class 1 SH2-like adaptor, to link GEF activity for trimeric Gαi to cytoplasmic tails of ligand-activated RTKs. Schematic illustration of the modular structure of GIV from amino- to carboxyl-terminus: phosphoinositide-binding domain (PI4P-BD, brown), which binds membrane lipid and helps localize GIV to the PI4P-enriched plasma (PM), where ligand-activated receptors and G proteins are located; a GEF motif (green), which binds and activates Gαi; a SH2 domain (blue), which recognizes and docks onto the autophosphorylation sites on cytoplasmic tails of ligand-activated EGFR and other RTKs; a pair of phosphotyrosines (P), which directly bind p85α (PI3K) and activate class 1A PI3Ks; and an actin-binding domain (actin-BD, purple), which binds and remodels actin at the leading edge of migrating cells. These binding events cooperatively maintain GIV at the PM such that Gαi and PI3K are activated, and actin is remodeled in close proximity to RTKs. Recruitment of GIV-SH2 to RTKs and activation of Gαi in the vicinity of activated receptors enable GIV to modulate signaling programs downstream of the receptor. The plasticity of GIV's SH2-like domain between a stably folded and partially folded state is likely to regulate GIV's ability to engage with activated RTKs.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Figure 8: Multimodular cooperation allows GIV, a class 1 SH2-like adaptor, to link GEF activity for trimeric Gαi to cytoplasmic tails of ligand-activated RTKs. Schematic illustration of the modular structure of GIV from amino- to carboxyl-terminus: phosphoinositide-binding domain (PI4P-BD, brown), which binds membrane lipid and helps localize GIV to the PI4P-enriched plasma (PM), where ligand-activated receptors and G proteins are located; a GEF motif (green), which binds and activates Gαi; a SH2 domain (blue), which recognizes and docks onto the autophosphorylation sites on cytoplasmic tails of ligand-activated EGFR and other RTKs; a pair of phosphotyrosines (P), which directly bind p85α (PI3K) and activate class 1A PI3Ks; and an actin-binding domain (actin-BD, purple), which binds and remodels actin at the leading edge of migrating cells. These binding events cooperatively maintain GIV at the PM such that Gαi and PI3K are activated, and actin is remodeled in close proximity to RTKs. Recruitment of GIV-SH2 to RTKs and activation of Gαi in the vicinity of activated receptors enable GIV to modulate signaling programs downstream of the receptor. The plasticity of GIV's SH2-like domain between a stably folded and partially folded state is likely to regulate GIV's ability to engage with activated RTKs.
Mentions: Besides this unique coexistence of GEF and SH2-like domains, GIV contains a growing list of many other of domains/motifs, cooperation between which could also be critical for its function as signal transducer (Figure 8). Here we demonstrated that GIV's GEF and SH2-like domains cooperate in the formation of RTK-GIV-Gαi ternary complexes and subsequent activation of Gαi. We also provided evidence that cooperation between GIV's SH2-like domain and its phosphotyrosines is essential for the formation of RTK-GIV-PI3K ternary complexes and subsequent activation of the PI3K/Akt pathway. That cells expressing SH2-deficient GIV mutants poorly remodel actin also suggests that SH2-like and actin-binding domains of GIV cooperate in linking EGF signaling to actin remodeling. It is likely that there are many more interdomain collaborations with the new discovered SH2-like domain—for example, the observed recruitment of GIV to the PM after growth factor stimulation is likely to be cooperatively mediated by its phosphatidylinositol 4-phosphate (PI4P) binding (Enomoto et al., 2005) and the SH2 domains. The coiled-coil domain, which mediates homo-oligomerization (Enomoto et al., 2005), could cooperate with the SH2-like domain to enhance clustering of RTK-GIV complexes at the PM. We propose that the SH2-like domain is key to achieve targeting and proximity of GIV to RTKs, which allows GIV to integrate incoming signals from these receptors and modulate them via activation of G proteins in the vicinity of the receptors. Examples of such interdomain collaborations were reported in the case of other multimodular signal transducers that bridge RTKs and small G proteins, such as Ras-GAP (Schlessinger and Lemmon, 2003), which inactivates Ras in the vicinity of ligand-activated receptors.

Bottom Line: We discovered a unifying mechanism that allows GIV/Girdin, a bona fide metastasis-related protein and a guanine-nucleotide exchange factor (GEF) for Gαi, to serve as a direct platform for multiple RTKs to activate Gαi proteins.Using a combination of homology modeling, protein-protein interaction, and kinase assays, we demonstrate that a stretch of ∼110 amino acids within GIV C-terminus displays structural plasticity that allows folding into a SH2-like domain in the presence of phosphotyrosine ligands.Expression of a SH2-deficient GIV mutant (Arg 1745→Leu) that cannot bind RTKs impaired all previously demonstrated functions of GIV-Akt enhancement, actin remodeling, and cell migration.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of California, San Diego, School of Medicine, CA 92093.

Show MeSH
Related in: MedlinePlus