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Keykavous Parang

Publications and source records attributed to Keykavous Parang.

32 records · Page 2Linked to original sources
PubMed2004

Carboxylic acid and phosphate ester derivatives of fluconazole: synthesis and antifungal activities.

Two classes of fluconazole derivatives, (a) carboxylic acid esters and (b) fatty alcohol and carbohydrate phosphate esters, were synthesized and evaluated in vitro against Cryptococcus neoformans, Candida albicans, and Aspergillus niger. All carboxylic acid ester derivatives of fluconazole (1a-l), such as O-2-bromooctanoylfluconazole (1g, MIC=111 microg/mL) and O-11-bromoundecanoylfluconazole (1j, MIC=198 microg/mL), exhibited higher antifungal activity than fluconazole (MIC > or = 4444 microg/mL) against C. albicans ATCC 14053 in SDB medium. Several fatty alcohol phosphate triester derivatives of fluconazole, such as 2a, 2b, 2f, 2g, and 2h, exhibited enhanced antifungal activities against C. albicans and/or A. niger compared to fluconazole in SDB medium. For example, 2-cyanoethyl-omega-undecylenyl fluconazole phosphate (2b) with MIC value of 122 microg/mL had at least 36 times greater antifungal activity than fluconazole against C. albicans in SDB medium. Methyl-undecanyl fluconazole phosphate (2f) with a MIC value of 190 microg/mL was at least 3-fold more potent than fluconazole against A. niger ATCC 16404. All compounds had higher estimated lipophilicity and dermal permeability than those for fluconazole. These results demonstrate the potential of these antifungal agents for further development as sustained-release topical antifungal chemotherapeutic agents.

Antifungal Agents↗
PubMed2004

ATP-phosphopeptide conjugates as inhibitors of Src tyrosine kinases.

A number of Src SH2 domain inhibitors enhance the kinase catalytic activity by switching the closed inactive to the open active conformation. ATP-phosphopeptide conjugates were designed and synthesized as Src tyrosine kinase inhibitors based on a tetrapeptide sequence pTyr-Glu-Glu-Ile (pYEEI) and ATP to block the SH2 domain signaling and substrate phosphorylation by ATP, respectively. In general, ATP-phosphopeptide conjugates with optimal linkers such as compounds 5 and 7 (K(i) = 1.7-2.6 microM) showed higher binding affinities to the ATP-binding site relative to the other ATP-phosphopeptide conjugates having short or long linkers, 1-4 and 6, (K(i) = 10.1-16.1 microM) and ATP (K(m) = 74 microM). These ATP-phosphopeptide conjugates may serve as novel templates for designing protein tyrosine kinase inhibitors to block SH2 mediated protein-protein interactions and to counter the activation of enzyme that resulted from the SH2 inhibition.

Adenosine Triphosphate↗
PubMed2004

Conformationally constrained peptide analogues of pTyr-Glu-Glu-Ile as inhibitors of the Src SH2 domain binding.

A series of conformationally constrained peptides were designed and synthesized as the Src SH2 domain ligands based on a tetrapeptide sequence pTyr-Glu-Glu-Ile (pYEEI). In general, the constrained peptides such as compounds 6, 7, and 11 (IC(50) = 1.1-1.5 microM) showed higher binding affinities to the Src SH2 domain relative to the corresponding linear peptides 8a, 9a, and 13a, respectively (IC(50) > 100 microM), and pYEEI (IC(50) = 6.5 microM), as evaluated by a fluorescence polarization assay. Molecular modeling studies revealed that in constrained peptides, the isoleucine side chain penetrates very deeply into the hydrophobic binding pocket (P + 3 site) of the Src SH2 domain. These constrained peptides can serve as novel templates for the design of small and nonpeptidic inhibitors of the Src SH2 domain.

Binding Sites↗
PubMed2004

Inhibitors of protein kinase signaling pathways: emerging therapies for cardiovascular disease.

Protein kinases are enzymes that covalently modify proteins by attaching phosphate groups (from ATP) to serine, threonine, and/or tyrosine residues. In so doing, the functional properties of the protein kinase's substrates are modified. Protein kinases transduce signals from the cell membrane into the interior of the cell. Such signals include not only those arising from ligand-receptor interactions but also environmental perturbations such as when the membrane undergoes mechanical deformation (ie, cell stretch or shear stress). Ultimately, the activation of signaling pathways that use protein kinases often culminates in the reprogramming of gene expression through the direct regulation of transcription factors or through the regulation of mRNA stability or protein translation. Protein kinases regulate most aspects of normal cellular function. The pathophysiological dysfunction of protein kinase signaling pathways underlies the molecular basis of many cancers and of several manifestations of cardiovascular disease, such as hypertrophy and other types of left ventricular remodeling, ischemia/reperfusion injury, angiogenesis, and atherogenesis. Given their roles in such a wide variety of disease states, protein kinases are rapidly becoming extremely attractive targets for drug discovery, probably second only to heterotrimeric G protein-coupled receptors (eg, angiotensin II). Here, we will review the reasons for this explosion in interest in inhibitors of protein kinases and will describe the process of identifying novel drugs directed against kinases. We will specifically focus on disease states for which drug development has proceeded to the point of clinical or advanced preclinical studies.

Animals↗
PubMed2004

Design of tetrapeptide ligands as inhibitors of the Src SH2 domain.

Src homology-2 (SH2) domains are noncatalytic motifs containing approximately 100 amino acid residues that are involved in intracellular signal transduction. The phosphotyrosine-containing tetrapeptide pTyr-Glu-Glu-Ile (pYEEI) binds to Src SH2 domain with high affinity (K(d)=100 nM). The development of five classes of tetrapeptides as inhibitors for the Src SH2 domain is described. Peptides were prepared via solid-phase peptide synthesis and tested for affinity to Src SH2 domain using a fluorescence polarization based assay. All of the N-terminal substituted pYEEI derivatives (class II) presented binding affinity (IC(50)=of 2.7-8.6 microM) comparable to pYEEI (IC(50)=6.5 microM) in this assay. C-Terminal substituted pYEEI derivatives (class III) showed a lower binding affinity with IC(50) values of 34-41 microM. Amino-substituted phenylalanine derivatives (class IV) showed weak binding affinities (IC(50)=16-153 microM). Other substitutions on phenyl ring (class I) or the replacement of the phenyl ring with other cyclic groups (class V) dramatically decreased the binding of tetrapeptides to Src SH2 (IC(50)>100 microM). The ability of pYEEI and several of the tetrapeptides to inhibit the growth of cancer cells were assessed in a cell-based proliferation assay in human embryonic kidney (HEK) 293 tumor cells. The binding affinity of several of tested compounds against Src SH2 domain correlates with antiproliferative activity in 293T cells. None of the compounds showed any significant antifungal activity against Candida albicans ATCC 14053 at the maximum tested concentration of 10 microM. Overall, these results provided the structure-activity relationships for some FEEI and YEEI derivatives designed as Src SH2 domain inhibitors.

Amides↗
PubMed2004

Total synthesis and in vitro-antifungal activity of (+/-)-2-methoxytetradecanoic Acid.

The marine fatty acid (+/-)-2-methoxytetradecanoic acid was synthesized in two steps (71% overall yield) starting from commercially available methyl-2-hydroxy-tetradecanoate. The title compound was antifungal against Candida albicans (ATCC 14053) in RPMI medium and Aspergillus niger (ATCC 16404) and Cryptococcus neoformans (ATCC 66031) in SDB medium at the minimum inhibitory concentration (MIC) of 100 mM, which compares to the fungitoxicity of a 2-iodotetradecanoic acid against the same fungi. The title compound was also five to ten times more cytotoxic than capric acid to C. albicans and A. niger in the tested medium but comparable in cytotoxicity to either capric acid and its 2-methoxylated analog to C. neoformans. The antifungal activity of (+/-)-2-methoxytetradecanoic acid is explained in terms of inhibition of N-myristoyltransferase.

Acyltransferases↗
PubMed2004

Design strategies for protein kinase inhibitors.

Deregulation of protein kinases due to mutation or overexpression is a hallmark of several diseases, for example, cancer, diabetes, inflammation and cardiovascular disorders. Consequently, there has been a growing interest in the discovery of protein kinase inhibitors as novel drugs. Here, we focus on key milestones and advances in protein kinase inhibitor drug discovery over the last year, with an emphasis on novel strategies such as targeting of single and multiple binding sites, inactive conformations of kinases, allosteric sites, regulatory domains and heat shock proteins. We will highlight recent developments for specific inhibitors in clinical studies for growth factor receptors, non-receptor tyrosine kinases and serine/threonine kinases.

Chemistry, Pharmaceutical↗
PubMed2003

Determination of the substrate-docking site of protein tyrosine kinase C-terminal Src kinase.

Protein tyrosine kinases (PTK) are key enzymes of mammalian signal transduction. For the fidelity of signal transduction, each PTK phosphorylates only one or a few proteins on specific Tyr residues. Substrate specificity is thought to be mediated by PTK-substrate docking interactions and recognition of the phosphorylation site sequence by the kinase active site. However, a substrate-docking site has not been determined on any PTK. C-terminal Src kinase (Csk) is a PTK that specifically phosphorylates Src family kinases on a C-terminal Tyr. In this study, by sequence alignment and site-specific mutagenesis, we located a substrate-docking site on Csk. Mutations in the docking site disabled Csk to phosphorylate, regulate, and complex with Src but only moderately affected its general kinase activity. A peptide mimicking the docking site potently inhibited (IC50 = 21 microM) Csk phosphorylation of Src but only moderately inhibited (IC50 = 422 microM) its general kinase activity. Determination of the substrate-docking site provides the structural basis of substrate specificity in Csk and a model for understanding substrate specificity in other PTKs.

Alanine↗
PubMed2003

Current targets for anticancer drug discovery.

The call for the discovery of less toxic, more selective, and more effective agents to treat cancer has become more urgent. Inhibition of angiogenesis continues to be one of the main streams in the current cancer drug discovery activity. Insights into tumor angiogenesis biology have led to the identification of a number of molecules, which are important for the progression of these processes. Of particular interest is a group of growth factors including fibroblast growth factor, platelet-derived growth factor, and vascular endothelial growth factor. These growth factors and their corresponding receptor tyrosine kinases have become important targets for inhibition of the proliferation of endothelial cells, the main component of blood vessels. The validated targets for inhibition of angiogenesis also include a family of matrix metalloproteinases and cell adhesion molecules. In the closely related area, protein kinases have emerged as one of the most important targets for drug discovery. Besides growth factor receptor tyrosine kinases, numerous other protein kinases implicated in malignancies have been identified including non-receptor kinases such as Bcl-Abl and Src kinases. In addition, the cell cycle regulators (cyclin-dependent kinases, p21 gene) and apoptosis modulators (Bcl-2 oncoprotein, p53 tumor suppressor gene, survivin protein, etc) have also attracted renewed interest as potential targets for anticancer drug discovery. Other molecular targets include protein farnesyltransferase (FTase), histone deacetylase (HDAC), and telomerase, which have essential roles in cellular signal transduction pathways (FTase, HDAC) and cell life-span (telomerase). This review presents a comprehensive summary and discussion on the most important targets currently attracting a great deal of interest in contemporary anticancer drug design and discovery. Recent advances complementing these targets are also highlighted.

Animals↗
PubMed2002

Polymer-supported reagents for methylphosphorylation and phosphorylation of carbohydrates.

Two polymer-supported reagents for methylphosphorylation and phosphorylation of carbohydrates have been developed. p-Hydroxybenzyl alcohol and beta-mercaptoethanol were immobilized on cross-linked divinylbenzene-polystyrene copolymer and conjugated with methyl N,N-diisopropylchlorophosphoramidite. Carbohydrates were reacted with polymer-bound phosphitylating reagents. Further oxidation, with or without the methoxy group deprotection, and cleavage yielded methylphosphorylated or phosphorylated carbohydrates, respectively.

Benzyl Alcohols↗
PubMed2002

Development of photo-crosslinking reagents for protein kinase-substrate interactions.

The identification of relevant protein kinase-protein substrate partners remains a serious challenge on a genome-wide scale. The design and synthesis of a photo-activatable nucleotide reagent to crosslink protein kinases with their substrates is described in which an azido group is appended to the gamma-phosphoryl and purine moieties of ATP. In the absence of UV, compounds of this class were shown to act as competitive inhibitors versus ATP and non-competitive inhibitors versus peptide substrate for the protein tyrosine kinase Csk, suggesting that they can form a ternary complex with kinase and protein substrate. In vitro experiments with protein kinases indicate the bifunctional reagent can induce covalent protein-protein crosslinking that is dependent on UV irradiation. That significant kinase-substrate crosslinking occurs is suggested by the fact that this crosslinking is competitively inhibited by ATP. The crosslinked adducts can be readily cleaved by phosphodiesterase which supports the model for crosslinking and provides a simple method to deconvolute the linked protein partners.

Adenosine Triphosphate↗
PubMedDate not supplied

Designing bisubstrate analog inhibitors for protein kinases.

Protein kinases play critical roles in signal transduction pathways by transmitting extracellular signals across the cell membrane to distant locations in the cytoplasm and the nucleus. The development of protein kinase inhibitors has been hindered by the broad overlapping substrate specificities exhibited by these enzymes. The design of bisubstrate analog inhibitors could provide for the enhancement of specificity and potency in protein kinase inhibition. Bisubstrate analog inhibitors form a special group of protein kinase inhibitors that mimic two natural substrates/ligands and that simultaneously associate with two regions of given kinases. Most bisubstrate analogs have been designed to mimic the phosphate donor (ATP) and the acceptor components (Ser-, Thr-, or Tyr-containing peptides). Recent studies have emphasized the importance of maintaining a specific distance between these two components to achieve potent inhibition. In this review, we present a discussion of the methods for designing protein kinase inhibitors by mechanism-based approaches. Emphasis is given to bivalent approaches, with an interpretation of what has been learned from more and less successful examples. Future challenges in this area are also highlighted.

Carrier Proteins↗