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Biomedical subjects

G Caravatti

Publications and source records attributed to G Caravatti.

At least 19 recordsLinked to original sources
PubMed2000

Synthesis and biological evaluation of highly potent analogues of epothilones B and D.

A series of new epothilone B and D analogues incorporating fused hetero-aromatic side chains have been prepared. The synthetic strategy is based on olefin 3 as the common intermediate and allows variation of the side-chain structure in a highly convergent and stereoselective manner. Epothilone analogues 1a-d and 2a-d are more potent inhibitors of cancer cell proliferation than the corresponding parent epothilones B or D.

Antineoplastic Agents↗
PubMed2000

Structure-based design and synthesis of phosphinate isosteres of phosphotyrosine for incorporation in Grb2-SH2 domain inhibitors. Part 1.

Based on X-ray crystal structure information, mono charged phosphinate isosteres of phosphotyrosine have been designed and incorporated in a short inhibitory peptide sequence of the Grb2-SH2 domain. The resulting compounds, by exploiting additional interactions, inhibit binding to the Grb2-SH2 domain as potently as the corresponding doubly charged (phosphonomethyl)phenylalanine analogue.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Selective GRB2 SH2 inhibitors as anti-Ras therapy.

Given the key role of Ras in the mitogenic signaling by receptor tyrosine kinases, several targets upstream of Ras may prove to be excellent targets for drugs in the treatment of cancer caused by oncogenic tyrosine kinases. CGP78850 is a potent competitor of Grb2 SH2-phosphopeptide interactions. This inhibitor has been obtained by rational drug design and is specific toward the Grb2 SH2 vs. other SH2 domains and the PTB domain of SHC in vitro. Accordingly, CGP78850 blocks epidermal growth factor receptor (EGFR)-Grb2 and Shc-Grb2 interactions in living cells. It also inhibits the growth of cells transformed by receptor tyrosine kinases, which transmit a proliferative signal through Grb2 to Ras, but not cells transformed by oncogenic Raf or cells that contain activating Ras mutations. Moreover, our results demonstrate that, in cells overexpressing receptor tyrosine kinases, such as the EGFR, Grb2 SH2 inhibitors induce expression of the cell cycle inhibitors p21(Waf1/Cip1/CAP1) and p27(Kip1) and reverse transformation.

3T3 Cells↗
PubMed1999

Effect of potent and selective inhibitors of the Grb2 SH2 domain on cell motility.

Cell motility has been correlated both with oncogenic invasiveness and metastatic potential. The development of selective inhibitors of motility has thus great potential importance. Grb2 is a SH2/SH3 domain-containing adaptor protein that links growth factor receptor tyrosine kinases to the Ras signaling pathway. We have developed specific small molecule inhibitors of the Grb2 SH2 domain as potential leads for drug discovery. Synthesis of the inhibitors and their effects on growth factor-induced growth in cells have been reported previously. In the current study, we establish that these inhibitors inhibit hepatocyte growth factor/scatter factor-induced A431 and Madin-Darby canine kidney cell motility and various cell motility-related events, including epidermal growth factor-induced ruffling of A431 cells and epidermal growth factor-induced translocation of the small GTPase Rac in these cells. We demonstrate for the first time a direct role for Grb2 in cell motility and indicate a new avenue for cancer therapeutics.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Structure-based design of a non-peptidic antagonist of the SH2 domain of GRB2.

The structure-based design and synthesis of a completely non-peptidic, micromolar antagonist of the SH2 domain of Grb2 is presented. The compound mimics the two main pharmacophores of the natural ligand, the phenylphosphate of the phosphotyrosine residue and the beta-carboxamide of the X+2 asparagine, which are linked by a rigid aromatic spacer.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Author errata.

Explore the source record for details and available documents.

Retraction Notice↗
PubMed1999

Highly potent inhibitors of the Grb2-SH2 domain.

Highly potent inhibitors of the Grb2-SH2 domain have been synthesized. They share the common sequence: Ac-Pmp-Ac6c-Asn-NH-(3-indolyl-propyl). Different substituents at the 3-indolyl-propylamine C-terminal group were explored to further improve the activity. This is the first example of inhibitors of SH2 domains with sub-nanomolar affinity reported to date.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Structure-based design of peptidomimetic ligands of the Grb2-SH2 domain.

We have designed and synthesized a (3-aminomethyl-phenyl)-urea scaffold to mimic the X+1-Asn part of the minimal phosphopeptide sequence, Ac-pTyr-X+1-Asn-NH2, recognized by the Grb2-SH2 domain. The resulting compounds show the same degree of affinity as their peptide counterparts for the Grb2-SH2 domain. This is the first example reported to date of ligands of the Grb2-SH2 domain with substantially reduced peptidic character.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Structure-based design and synthesis of high affinity tripeptide ligands of the Grb2-SH2 domain.

The X-ray structure of the Grb2-SH2 domain in complex with a specific phosphopeptide ligand has revealed the existence of an extended hydrophobic area adjacent to the primary binding site of the ligand on the SH2 domain. This has been exploited to design hydrophobic C-terminal groups that improve the binding affinity of the minimal sequence pTyr-Ile-Asn recognized by the Grb2-SH2 domain. The most significant increase in affinity (25-fold compared to that of the reference peptide having a nonsubstituted carboxamide C-terminus) was obtained with a 3-naphthalen-1-yl-propyl group which was predicted to have the largest contact area with the SH2 domain hydrophobic region. This modification combined with replacement of the minimal sequence isoleucine residue by 1-aminocyclohexane carboxylic acid to stabilize the beta-turn conformation required for recognition by the Grb2-SH2 domain resulted in the high affinity (47 nM in an ELISA assay) and selective phosphopeptide Ac-pTyr-Ac6c-Asn-NH(3-naphthalen-1-yl-propyl).

Adaptor Proteins, Signal Transducing↗
PubMed1998

Structural basis for the high affinity of amino-aromatic SH2 phosphopeptide ligands.

An anthranyl moiety placed at the N terminus of a phosphotyrosine peptide potentiates the inhibitory effect of this small peptide on the binding of the Grb2 SH2 domain to the EGF receptor. Using molecular modeling procedures based on the Lck SH2 domain structure, this observation was rationalized in terms of a suitably favorable pi-pi stacking interaction between the anthranyl moiety and the arginine alphaA2 (ArgalphaA2) residue side-chain of Grb2 SH2. The crystal structure of the Grb2 SH2 domain in complex with the inhibitor 2-Abz-EpYINQ-NH2 (IC50 26 nM) has been solved in two different crystal forms at 2.1 and 1.8 A resolution. This structure confirms the modeling based on the Lck SH2 domain. The ArgalphaA2 residue is conserved in most SH2 domains. Thus, as expected, the anthranyl group also confers high affinity to small peptide ligands of other SH2 domains such as Lck-, PLC-gamma-amino-terminal and p85 amino-terminal SH2 domains as demonstrated by structure affinity relationships (SAR) data. These potent peptides with an amino-terminal surrogate group and the structure of Grb2 SH2 domain in complex with one such peptide represent good starting points for the design and optimization of new inhibitors of many SH2 domains.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Discovery of 3-aminobenzyloxycarbonyl as an N-terminal group conferring high affinity to the minimal phosphopeptide sequence recognized by the Grb2-SH2 domain.

The observation that anthranilic acid as N-terminal group produces a dramatic increase of the binding affinity of the phosphopeptide sequence Glu-pTyr-Ile-Asn for the Grb2-SH2 domain was rationalized by molecular modeling. The model, which invokes a stacking interaction between the N-terminal group and the SH2 domain residue Arg alpha A2, was subsequently used to design the 3-aminobenzyloxycarbonyl N-terminal group. The latter confers high affinity (IC50 = 65 nM in an ELISA assay) to the minimal sequence pTyr-Ile-Asn recognized by the Grb2-SH2 domain.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Dual specificity of Src homology 2 domains for phosphotyrosine peptide ligands.

SH2 domains mediate protein-protein interactions and are involved in a wide range of intracellular signaling events. SH2 domains are 100-amino acid stretches of protein that bind to other proteins containing phosphotyrosine residues. A current major research goal is formulation of the structural principles which govern peptide-binding specificity in SH2 domains. Several structures (both X-ray and NMR) of SH2 domains have now been determined. Short peptide fragments on the carboxyl-terminal side of the phosphotyrosine residue carry the sequence specific information for SH2 recognition. The bound peptides are held in an extended conformation. However, for the GRB2 SH2 domain, the peptide adopts a beta-turn as the motif for recognition [Rahuel, J., et al. (1996) Nat. Struct. Biol. 3, 586-589]. Our SAR data and molecular modeling studies suggest that many SH2 domains, such as the SH2 domains of Lck, Src, and p85, can interact with high affinity with short peptide sequences at least in two ways which are sequence-dependent. The peptide forms either an extended chain across the D-strand of SH2 domains with anchors at pY and pY+3 or, as in the case of GRB2 SH2, a beta-turn with anchors at pY and pY+2. Due to a bulky tryptophan in its EF1 loop, GRB2 SH2 cannot bind peptide conformations such as the extended chain and thus has a unique specificity.

Animals↗
PubMed1996

Phenylamino-pyrimidine (PAP) derivatives: a new class of potent and selective inhibitors of protein kinase C (PKC).

Phenylamino-pyrimidines represent a novel class of inhibitors of the protein kinase C with a high degree of selectivity versus other serine/threonine and tyrosine kinases. Steady state kinetic analysis of N-(3-[1-imidazolyl]-phenyl-4-(3-pyridyl)-2-pyrimidinamine (5), which showed potent inhibitory activity, revealed competitive kinetics relative to ATP. The adjacent H-bond acceptor of the pyrimidine moiety next to an H-bond donor of the phenylamine was found to be crucial for inhibitory activity. N-(3-Nitro-phenyl)-4-(3-pyridyl)-2-pyrimidinamine (7) preferentially inhibited PKC-alpha (IC50 = 0.79 microM) and not the other subtypes tested. The inhibition constants of PKC-alpha and the antiproliferative effect on T24 human bladder carcinoma cells showed a qualitative correlation, although with some exceptions.

Aniline Compounds↗
PubMed1996

In vitro trypanocidal activities of new S-adenosylmethionine decarboxylase inhibitors.

A series of novel aromatic derivatives based on the structure of methylglyoxal bis(guanylhydrazone) (MGBG) was examined for in vitro antitrypanosomal activities and cytotoxicities for human cells. One-third of the compounds tested showed trypanocidal activity at concentrations below 0.5 microM after an incubation period of 72 h. Structure-activity analysis revealed that bicyclic compounds with homocyclic rings and unmodified termini were the most active compounds. Results obtained in three laboratories employing different methods and trypanosome populations consistently ranked compound CGP 40215A highest. This compound had a 50% inhibitory concentration of 0.0045 microM for Trypanosoma brucei rhodesiense, was also active against other trypanosome species, including a multidrug-resistant Trypanosoma brucei brucei, and was significantly less toxic than other compounds tested for a human adenocarcinoma cell line, with a 50% inhibitory concentration of 1.14 mM. The effect of CGP 40215A was time and dose dependent, and low concentrations of the compound required exposure times of > 2 days to exert trypanocidal activity. Compounds were inactive against Leishmania donovani and Trypanosoma cruzi amastigotes in murine macrophages in vitro.

Adenocarcinoma↗
PubMed1995

Modelling study of protein kinase inhibitors: binding mode of staurosporine and origin of the selectivity of CGP 52411.

A model for the binding mode of the potent protein kinase inhibitor staurosporine is proposed. Using the information provided by the crystal structure of the cyclic-AMP-dependent protein kinase, it is suggested that staurosporine, despite a seemingly unrelated chemical structure, exploits the same key hydrogen-bond interactions as ATP, the cofactor of the protein kinases, in its binding mode. The structure-activity relationship of the inhibitor and a docking analysis give strong support to this hypothesis. The selectivity of the dianilinophthalimide inhibitor CGP 52411 towards the EGF-receptor protein tyrosine kinase is rationalized on the basis of the model. It is proposed that this selectivity originates in the occupancy, by one of the anilino moieties of the inhibitor, of the region of the enzyme cleft that normally binds the ribose ring of ATP, which appears to possess a marked lipophilic character in this kinase.

Alkaloids↗