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Your search keyword '"Ponzanelli I"' showing total 3 results
Start Over Author "Ponzanelli I" Topic adaptor proteins, signal transducing
3 results on '"Ponzanelli I"'

1. The eps8 family of proteins links growth factor stimulation to actin reorganization generating functional redundancy in the Ras/Rac pathway.

Author

Offenhäuser N, Borgonovo A, Disanza A, Romano P, Ponzanelli I, Iannolo G, Di Fiore PP, and Scita G

Subjects
Actins metabolism, Animals, Blotting, Northern, Cell Surface Extensions metabolism, Cells, Cultured, Cloning, Molecular, Cytoskeleton metabolism, Female, Fluorescent Antibody Technique, Indirect, Humans, In Situ Hybridization, Intracellular Signaling Peptides and Proteins, Male, Mice, Protein Binding physiology, Protein Isoforms genetics, Protein Isoforms metabolism, Protein Structure, Tertiary, Proteins genetics, Proto-Oncogene Proteins c-akt, Sequence Homology, Signal Transduction, Tissue Distribution, Adaptor Proteins, Signal Transducing, Cytoskeletal Proteins metabolism, Phosphatidylinositol 3-Kinases metabolism, Protein Serine-Threonine Kinases metabolism, Proteins metabolism, SOS1 Protein metabolism
Abstract

Sos-1, a guanine nucleotide exchange factor (GEF), eps8 and Abi1, two signaling proteins, and the lipid kinase phosphoinositide 3-kinase (PI3-K), assemble in a multimolecular complex required for Rac activation leading to actin cytoskeletal remodeling. Consistently, eps8 -/- fibroblasts fail to form membrane ruffles in response to growth factor stimulation. Surprisingly, eps8 null mice are healthy, fertile, and display no overt phenotype, suggesting the existence of functional redundancy within this pathway. Here, we describe the identification and characterization of a family of eps8-related proteins, comprising three novel gene products, named eps8L1, eps8L2, and eps8L3. Eps8Ls display collinear topology and 27-42% identity to eps8. Similarly to eps8, eps8Ls interact with Abi1 and Sos-1; however, only eps8L1 and eps8L2 activate the Rac-GEF activity of Sos-1, and bind to actin in vivo. Consistently, eps8L1 and eps8L2, but not eps8L3, localize to PDGF-induced, F-actin-rich ruffles and restore receptor tyrosine kinase (RTK)-mediated actin remodeling when expressed in eps8 -/- fibroblasts. Thus, the eps8Ls define a novel family of proteins responsible for functional redundancy in the RTK-activated signaling pathway leading to actin remodeling. Finally, the patterns of expression of eps8 and eps8L2 in mice are remarkably overlapping, thus providing a likely explanation for the lack of overt phenotype in eps8 null mice.

Published
2004
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2. An effector region in Eps8 is responsible for the activation of the Rac-specific GEF activity of Sos-1 and for the proper localization of the Rac-based actin-polymerizing machine.

Author

Scita G, Tenca P, Areces LB, Tocchetti A, Frittoli E, Giardina G, Ponzanelli I, Sini P, Innocenti M, and Di Fiore PP

Subjects
Animals, Carrier Proteins genetics, Cell Fractionation, Cell Surface Extensions, Cells, Cultured, Culture Media, Serum-Free, Cytochalasin D pharmacology, Cytoskeletal Proteins, Embryo, Mammalian cytology, Fibroblasts drug effects, Fibroblasts metabolism, Genes, Reporter, Humans, Immunoblotting, Intracellular Signaling Peptides and Proteins, Mice, Microscopy, Fluorescence, Nucleic Acid Synthesis Inhibitors pharmacology, Peptide Fragments genetics, Peptide Fragments metabolism, Protein Structure, Tertiary, Proteins genetics, Recombinant Fusion Proteins genetics, Recombinant Fusion Proteins metabolism, SOS1 Protein genetics, Signal Transduction physiology, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Transfection, cdc42 GTP-Binding Protein metabolism, rac GTP-Binding Proteins genetics, ras Proteins genetics, Actins metabolism, Adaptor Proteins, Signal Transducing, Carrier Proteins metabolism, Proteins metabolism, SOS1 Protein metabolism, rac GTP-Binding Proteins metabolism, ras Proteins metabolism
Abstract

Genetic and biochemical evidence demonstrated that Eps8 is involved in the routing of signals from Ras to Rac. This is achieved through the formation of a tricomplex consisting of Eps8-E3b1-Sos-1, which is endowed with Rac guanine nucleotide exchange activity. The catalytic subunit of this complex is represented by Sos-1, a bifunctional molecule capable of catalyzing guanine nucleotide exchange on Ras and Rac. The mechanism by which Sos-1 activity is specifically directed toward Rac remains to be established. Here, by performing a structure-function analysis we show that the Eps8 output function resides in an effector region located within its COOH terminus. This effector region, when separated from the holoprotein, activates Rac and acts as a potent inducer of actin polymerization. In addition, it binds to Sos-1 and is able to induce Rac-specific, Sos-1-dependent guanine nucleotide exchange activity. Finally, the Eps8 effector region mediates a direct interaction of Eps8 with F-actin, dictating Eps8 cellular localization. We propose a model whereby the engagement of Eps8 in a tricomplex with E3b1 and Sos-1 facilitates the interaction of Eps8 with Sos-1 and the consequent activation of an Sos-1 Rac-specific catalytic ability. In this complex, determinants of Eps8 are responsible for the proper localization of the Rac-activating machine to sites of actin remodeling.

Published
2001
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3. Phosphoinositide 3-kinase activates Rac by entering in a complex with Eps8, Abi1, and Sos-1

Author

Saskia M. Brachmann, Isabella Ponzanelli, John R. Falck, Pier Paolo Di Fiore, Giorgio Scita, Emanuela Frittoli, Metello Innocenti, Innocenti, M, Frittoli, E, Ponzanelli, I, Falck, J, Brachmann, S, Di Fiore, P, and Scita, G

Subjects
PI3K, Receptor tyrosine kinase, Mice, Phosphatidylinositol 3-Kinases, 0302 clinical medicine, Phosphoprotein Phosphatases, GEF, Chromatography, High Pressure Liquid, Glutathione Transferase, 0303 health sciences, biology, ABI1, rac GTP-Binding Proteins, Cell biology, Rac GTP-Binding Proteins, 030220 oncology & carcinogenesis, COS Cells, Guanine nucleotide exchange factor, Signal transduction, SOS1 Protein, Protein Binding, Signal Transduction, RTK, Genetic Vectors, Molecular Sequence Data, Transfection, Models, Biological, Actin remodeling, EPS8, 03 medical and health sciences, Report, Animals, Amino Acid Sequence, Adaptor Proteins, Signal Transducing, 030304 developmental biology, Phosphoinositide 3-kinase, Arabidopsis Proteins, Proteins, actin remodeling, signaling, Cell Biology, Fibroblasts, Precipitin Tests, Signaling, Protein Structure, Tertiary, Enzyme Activation, Cytoskeletal Proteins, enzymes and coenzymes (carbohydrates), Microscopy, Fluorescence, biology.protein
Abstract

Class I phosphoinositide 3-kinases (PI3Ks) are implicated in many cellular responses controlled by receptor tyrosine kinases (RTKs), including actin cytoskeletal remodeling. Within this pathway, Rac is a key downstream target/effector of PI3K. However, how the signal is routed from PI3K to Rac is unclear. One possible candidate for this function is the Rac-activating complex Eps8–Abi1–Sos-1, which possesses Rac-specific guanine nucleotide exchange factor (GEF) activity. Here, we show that Abi1 (also known as E3b1) recruits PI3K, via p85, into a multimolecular signaling complex that includes Eps8 and Sos-1. The recruitment of p85 to the Eps8–Abi1–Sos-1 complex and phosphatidylinositol 3, 4, 5 phosphate (PIP3), the catalytic product of PI3K, concur to unmask its Rac-GEF activity in vitro. Moreover, they are indispensable for the activation of Rac and Rac-dependent actin remodeling in vivo. On growth factor stimulation, endogenous p85 and Abi1 consistently colocalize into membrane ruffles, and cells lacking p85 fail to support Abi1-dependent Rac activation. Our results define a mechanism whereby propagation of signals, originating from RTKs or Ras and leading to actin reorganization, is controlled by direct physical interaction between PI3K and a Rac-specific GEF complex.

Published
2003
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