CGP 52411

Retinoic acid-induced RB (retinoblastoma) hypophosphorylation enhanced by CGP 52411 (4,5-dianilinophthalimide), an EGF family tyrosine kinase receptor inhibitor.[Pubmed:8741214]

Eur J Cell Biol. 1996 Apr;69(4):327-34.

Retinoic acid is a known morphogen which can regulate cell proliferation and differentiation and also induces the hypophosphorylation of the RB (retinoblastoma tumor suppressor gene) protein, a known cell cycle regulatory protein. The mechanism by which these processes occur is unclear. We find that these processes can be regulated by CGP 52411, 4,5-dianilinophthalimide, an inhibitor of tyrosine protein kinases of the EGF receptor subfamily. Retinoic acid causes the largely phosphorylated RB protein expressed in proliferating HL-60 human promyelocytic leukemia cells to shift to the unphosphorylated form, as well as causing the cells to G0 arrest and differentiate. Addition of CGP 52411 accelerated the redistribution of the RB protein expressed in HL-60 cells to the unphosphorylated form, enhancing the effects of the retinoic acid. By itself CGP 52411 had no apparent effect on the RB protein expressed in HL-60 cells. CGP 52411 also accelerated the retinoic acid-induced accumulation of cells in G1/0 and the phenotypic conversion of cells to the mature myeloid phenotype, suggesting that its target is common to the regulation of both RB phosphorylation and cell proliferation and differentiation. CGP 52411 had a similar effect on the RB phosphorylation shift induced by 1,25-dihydroxy vitamin D3, a ligand for a receptor in the same steroid thyroid hormone superfamily as retinoic acid. Increasing the concentration of CGP 52411 enhanced the acceleration of RB hypophosphorylation in the case of both retinoic acid and 1,25-dihydroxy vitamin D3. The data are consistent with the negative regulation of retinoic acid induced RB protein dephosphorylation coupled to cell cycle arrest and differentiation by a receptor tyrosine kinase sensitive to CGP 52411.

Modelling study of protein kinase inhibitors: binding mode of staurosporine and origin of the selectivity of CGP 52411.[Pubmed:8789188]

J Comput Aided Mol Des. 1995 Dec;9(6):465-72.

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.

Direct and selective elimination of specific prions and amyloids by 4,5-dianilinophthalimide and analogs.[Pubmed:18480256]

Proc Natl Acad Sci U S A. 2008 May 20;105(20):7159-64.

Mechanisms to safely eliminate amyloids and preamyloid oligomers associated with many devastating diseases are urgently needed. Biophysical principles dictate that small molecules are unlikely to perturb large intermolecular protein-protein interfaces, let alone extraordinarily stable amyloid interfaces. Yet 4,5-dianilinophthalimide (DAPH-1) reverses Abeta42 amyloidogenesis and neurotoxicity, which is associated with Alzheimer's disease. Here, we show that DAPH-1 and select derivatives are ineffective against several amyloidogenic proteins, including tau, alpha-synuclein, Ure2, and PrP, but antagonize the yeast prion protein, Sup35, in vitro and in vivo. This allowed us to exploit several powerful new tools created for studying the conformational transitions of Sup35 and decipher the mechanisms by which DAPH-1 and related compounds antagonize the prion state. During fibrillization, inhibitory DAPHs alter the folding of Sup35's amyloidogenic core, preventing amyloidogenic oligomerization and specific recognition events that nucleate prion assembly. Select DAPHs also are capable of attacking preformed amyloids. They remodel Sup35 prion-specific intermolecular interfaces to create morphologically altered aggregates with diminished infectivity and self-templating activity. Our studies provide mechanistic insights and reinvigorate hopes for small-molecule therapies that specifically disrupt intermolecular amyloid contacts.

Efficient reversal of Alzheimer's disease fibril formation and elimination of neurotoxicity by a small molecule.[Pubmed:15388848]

Proc Natl Acad Sci U S A. 2004 Oct 5;101(40):14326-32.

The Abeta1-42 peptide that is overproduced in Alzheimer's disease (AD) from a large precursor protein has a normal amino acid sequence but, when liberated, misfolds at neutral pH to form "protofibrils" and fibrils that are rich in beta-sheets. We find that these protofibrils or fibrils are toxic to certain neuronal cells that carry Ca-permeant alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Disrupting the structure of the Abeta1-42 fibrils and protofibrils might lead to the discovery of molecules that would be very useful in the treatment of AD. A high-throughput screen of a library of >3,000 small molecules with known "biological activity" was set up to find compounds that efficiently decrease the beta-sheet content of aggregating Abeta1-42. Lead compounds were characterized by using thioflavin T (ThT) as a beta-sheet assay. The most effective of six compounds found was 4,5-dianilinophthalimide (DAPH) under the following conditions: DAPH at low micromolar concentrations abolishes or greatly reduces previously existing fully formed Abeta1-42 fibrils, producing instead amorphous materials without fibrils but apparently containing some protofibrils and smaller forms. Coincubation of the Abeta1-42 peptide with DAPH produces either amorphous materials or empty fields. Coincubation of DAPH and Abeta1-42 greatly reduces the beta-sheet content, as measured with ThT fluorescence, and produces a novel fluorescent complex with ThT. When the Abeta1-42 peptide was coincubated with DAPH at very low micromolar concentrations, the neuronal toxicity mentioned above (Ca(2+) influx) was eliminated. Clearly, DAPH is a promising candidate for AD therapy.

4,5-Dianilinophthalimide: a protein-tyrosine kinase inhibitor with selectivity for the epidermal growth factor receptor signal transduction pathway and potent in vivo antitumor activity.[Pubmed:8134396]

Proc Natl Acad Sci U S A. 1994 Mar 15;91(6):2334-8.

Deregulated signal transduction via the epidermal growth factor receptor (EGF-R) family of protein-tyrosine kinase growth factor receptors is associated with proliferative diseases. We describe a class of compounds (4,5-dianilinophthalimides) that inhibit the EGF-R protein-tyrosine kinase in vitro with high selectivity. In cells, 4,5-dianilinophthalmide selectively inhibited both ligand-induced EGF-R and p185c-erbB2 autophosphorylation and c-fos mRNA induction. Antitumor activity could be demonstrated in vivo against xenografts of the A431 and SK-OV-3 tumors, which overexpress the EGF-R and p185c-erbB2, respectively. In contrast, a platelet-derived growth factor-driven tumor was not inhibited by 4,5-dianilinophthalimide, which is compatible with its cellular selectivity and hypothesized mechanism of action. No overt cumulative toxicity was observed during treatment even though high efficacy was observed, indicating a good therapeutic window. 4,5-Dianilinophthalimides may offer therapeutic agents for the treatment of hyperproliferative diseases that overexpress EGF-R family protein-tyrosine kinases or their ligands.

CGP52411 (DAPH) is a high selective, potent, orally active and ATP-competitive EGFR inhibitor with an IC50 of 0.3 μM. CGP52411 blocks the toxic influx of Ca2+ ions into neuronal cells, and dramatic inhibits and reverses the formation of β-amyloid (Aβ42) fibril aggregates associated with Alzheimer's disease.

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