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Direct interaction of insulin-like growth factor-1 receptor with leukemia-associated RhoGEF.

Taya S, Inagaki N, Sengiku H, Makino H, Iwamatsu A, Urakawa I, Nagao K, Kataoka S, Kaibuchi K - J. Cell Biol. (2001)

Bottom Line: Here, we identified leukemia-associated Rho guanine nucleotide exchange factor (GEF) (LARG), which contains the PSD-95/Dlg/ZO-1 (PDZ), regulator of G protein signaling (RGS), Dbl homology, and pleckstrin homology domains, as a nonphosphorylated IGF-1 receptor-interacting molecule.When MDCKII epithelial cells were treated with IGF-1, Rho and its effector Rho-associated kinase (Rho-kinase) were activated and actin stress fibers were enhanced.Taken together, these results indicate that IGF-1 activates the Rho/Rho-kinase pathway via a LARG/IGF-1 receptor complex and thereby regulates cytoskeletal rearrangements.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Showa-ku, Nagoya 466-8550, Japan.

ABSTRACT
Insulin-like growth factor (IGF)-1 plays crucial roles in growth control and rearrangements of the cytoskeleton. IGF-1 binds to the IGF-1 receptor and thereby induces the autophosphorylation of this receptor at its tyrosine residues. The phosphorylation of the IGF-1 receptor is thought to initiate a cascade of events. Although various signaling molecules have been identified, they appear to interact with the tyrosine-phosphorylated IGF-1 receptor. Here, we identified leukemia-associated Rho guanine nucleotide exchange factor (GEF) (LARG), which contains the PSD-95/Dlg/ZO-1 (PDZ), regulator of G protein signaling (RGS), Dbl homology, and pleckstrin homology domains, as a nonphosphorylated IGF-1 receptor-interacting molecule. LARG formed a complex with the IGF-1 receptor in vivo, and the PDZ domain of LARG interacted directly with the COOH-terminal domain of IGF-1 receptor in vitro. LARG had an exchange activity for Rho in vitro and induced the formation of stress fibers in NIH 3T3 fibroblasts. When MDCKII epithelial cells were treated with IGF-1, Rho and its effector Rho-associated kinase (Rho-kinase) were activated and actin stress fibers were enhanced. Furthermore, the IGF-1-induced Rho-kinase activation and the enhancement of stress fibers were inhibited by ectopic expression of the PDZ and RGS domains of LARG. Taken together, these results indicate that IGF-1 activates the Rho/Rho-kinase pathway via a LARG/IGF-1 receptor complex and thereby regulates cytoskeletal rearrangements.

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GEF activity of LARG for the Rho family GTPases in vitro. (A) The effect of LARG on the dissociation of GDP from RhoA in vitro. The DH/PH domain of LARG and Dbl enhanced the dissociation of [3H]-labeled GDP from RhoA in a time-dependent manner. (B) The effect of LARG on other small GTPases in vitro. The DH/PH domain of LARG showed an exchange activity for RhoA but not one for Rac1, Cdc42, or Ras. The results shown are representative of three independent experiments.
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fig4: GEF activity of LARG for the Rho family GTPases in vitro. (A) The effect of LARG on the dissociation of GDP from RhoA in vitro. The DH/PH domain of LARG and Dbl enhanced the dissociation of [3H]-labeled GDP from RhoA in a time-dependent manner. (B) The effect of LARG on other small GTPases in vitro. The DH/PH domain of LARG showed an exchange activity for RhoA but not one for Rac1, Cdc42, or Ras. The results shown are representative of three independent experiments.

Mentions: We examined the GEF activity for the Rho family GTPases in vitro. In this assay, we used a GST fusion protein carrying the DH/PH domain of LARG for monitoring the exchange activity toward the Rho family GTPases. The DH/PH domain of LARG enhanced the dissociation of [3H]-labeled GDP from RhoA in a time-dependent manner under the conditions where Dbl stimulated the dissociation of GDP from RhoA (Fig. 4 A). To investigate whether LARG is a specific GEF for Rho, we further examined the effect of the DH/PH domain of LARG on other small GTPases, Rac1, Cdc42, and Ras. The DH/PH domain of LARG showed an exchange activity for RhoA but not for Rac1, Cdc42, or Ras (Fig. 4 B). These results indicate that LARG has the exchange activity for RhoA in vitro but not for Rac1, Cdc42, or Ras.


Direct interaction of insulin-like growth factor-1 receptor with leukemia-associated RhoGEF.

Taya S, Inagaki N, Sengiku H, Makino H, Iwamatsu A, Urakawa I, Nagao K, Kataoka S, Kaibuchi K - J. Cell Biol. (2001)

GEF activity of LARG for the Rho family GTPases in vitro. (A) The effect of LARG on the dissociation of GDP from RhoA in vitro. The DH/PH domain of LARG and Dbl enhanced the dissociation of [3H]-labeled GDP from RhoA in a time-dependent manner. (B) The effect of LARG on other small GTPases in vitro. The DH/PH domain of LARG showed an exchange activity for RhoA but not one for Rac1, Cdc42, or Ras. The results shown are representative of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2150867&req=5

fig4: GEF activity of LARG for the Rho family GTPases in vitro. (A) The effect of LARG on the dissociation of GDP from RhoA in vitro. The DH/PH domain of LARG and Dbl enhanced the dissociation of [3H]-labeled GDP from RhoA in a time-dependent manner. (B) The effect of LARG on other small GTPases in vitro. The DH/PH domain of LARG showed an exchange activity for RhoA but not one for Rac1, Cdc42, or Ras. The results shown are representative of three independent experiments.
Mentions: We examined the GEF activity for the Rho family GTPases in vitro. In this assay, we used a GST fusion protein carrying the DH/PH domain of LARG for monitoring the exchange activity toward the Rho family GTPases. The DH/PH domain of LARG enhanced the dissociation of [3H]-labeled GDP from RhoA in a time-dependent manner under the conditions where Dbl stimulated the dissociation of GDP from RhoA (Fig. 4 A). To investigate whether LARG is a specific GEF for Rho, we further examined the effect of the DH/PH domain of LARG on other small GTPases, Rac1, Cdc42, and Ras. The DH/PH domain of LARG showed an exchange activity for RhoA but not for Rac1, Cdc42, or Ras (Fig. 4 B). These results indicate that LARG has the exchange activity for RhoA in vitro but not for Rac1, Cdc42, or Ras.

Bottom Line: Here, we identified leukemia-associated Rho guanine nucleotide exchange factor (GEF) (LARG), which contains the PSD-95/Dlg/ZO-1 (PDZ), regulator of G protein signaling (RGS), Dbl homology, and pleckstrin homology domains, as a nonphosphorylated IGF-1 receptor-interacting molecule.When MDCKII epithelial cells were treated with IGF-1, Rho and its effector Rho-associated kinase (Rho-kinase) were activated and actin stress fibers were enhanced.Taken together, these results indicate that IGF-1 activates the Rho/Rho-kinase pathway via a LARG/IGF-1 receptor complex and thereby regulates cytoskeletal rearrangements.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Showa-ku, Nagoya 466-8550, Japan.

ABSTRACT
Insulin-like growth factor (IGF)-1 plays crucial roles in growth control and rearrangements of the cytoskeleton. IGF-1 binds to the IGF-1 receptor and thereby induces the autophosphorylation of this receptor at its tyrosine residues. The phosphorylation of the IGF-1 receptor is thought to initiate a cascade of events. Although various signaling molecules have been identified, they appear to interact with the tyrosine-phosphorylated IGF-1 receptor. Here, we identified leukemia-associated Rho guanine nucleotide exchange factor (GEF) (LARG), which contains the PSD-95/Dlg/ZO-1 (PDZ), regulator of G protein signaling (RGS), Dbl homology, and pleckstrin homology domains, as a nonphosphorylated IGF-1 receptor-interacting molecule. LARG formed a complex with the IGF-1 receptor in vivo, and the PDZ domain of LARG interacted directly with the COOH-terminal domain of IGF-1 receptor in vitro. LARG had an exchange activity for Rho in vitro and induced the formation of stress fibers in NIH 3T3 fibroblasts. When MDCKII epithelial cells were treated with IGF-1, Rho and its effector Rho-associated kinase (Rho-kinase) were activated and actin stress fibers were enhanced. Furthermore, the IGF-1-induced Rho-kinase activation and the enhancement of stress fibers were inhibited by ectopic expression of the PDZ and RGS domains of LARG. Taken together, these results indicate that IGF-1 activates the Rho/Rho-kinase pathway via a LARG/IGF-1 receptor complex and thereby regulates cytoskeletal rearrangements.

Show MeSH
Related in: MedlinePlus