Current status and future prospects of C1 domain ligands as drug candidates.
ABSTRACT The second messenger diacylglycerol (DAG) plays a central role in the signal transduction of G-protein coupled receptors and receptor tyrosine kinases by binding to C1 domain of effector proteins. C1 domain was first identified in protein kinase C (PKC) which comprises a family of ten isoforms that play roles in diverse cellular processes such as proliferation, apoptosis and differentiation. Aberrant signaling through PKC isoforms and other C1 domain-containing proteins has been implicated in several pathological disorders. Drug discovery concerning C1 domains has exploited both natural products and rationally designed compounds. Currently, molecules from several classes of C1 domain-binding compounds are in clinical trials; however, still more have the potential to enter the drug development pipeline. This review gives a summary of the recent developments in C1 domain-binding compounds.
- SourceAvailable from: Victor E Marquez[Show abstract] [Hide abstract]
ABSTRACT: The development of selective agents capable of discriminating between protein kinase C (PKC) isoforms and other diacylglycerol (DAG)-responsive C1 domain-containing proteins represents an important challenge. Recent studies have highlighted the role that Ras guanine nucleotide-releasing protein (RasGRP) isoforms play both in immune responses as well as in the development of prostate cancer and melanoma, suggesting that the discovery of selective ligands could have potential therapeutic value. Thus far, the N-methyl-substituted indololactone 1 is the agonist with the highest reported potency and selectivity for RasGRP relative to PKC. Here we present the synthesis, binding studies, cellular assays and biophysical analysis of interactions with model membranes of a family of regioisomers of 1 (compounds 2-5) that differ in the position of the linkage between the indole ring and the lactone moiety. These structural variations were studied to explore the interaction of the active complex (C1 domain-ligand) with cellular membranes, which is believed to be an important factor for selectivity in the activation of DAG-responsive C1 domain containing signaling proteins. All compounds were potent and selective activators of RasGRP when compared to PKCα with selectivities ranging from 6 to 65 fold. However, the parent compound 1 was appreciably more selective than any of the other isomers. In intact cells, modest differences in the patterns of translocation of the C1 domain targets were observed. Biophysical studies using giant vesicles as model membranes did show substantial differences in terms of molecular interactions impacting lipid organization, dynamics and membrane insertion. However, these differences did not yield correspondingly large changes in patterns of biological response, at least for the parameters examined.Bioorganic & medicinal chemistry 04/2014; · 2.82 Impact Factor
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ABSTRACT: Diacylglycerol (DAG) is a central mediator of signaling pathways that regulate cell proliferation, survival and apoptosis. Therefore, C1 domain, the DAG binding site within protein kinase C (PKC) and other DAG effector proteins, is considered a potential cancer drug target. Derivatives of 5-(hydroxymethyl)isophthalic acid are a novel group of C1 domain ligands with antiproliferative and differentiation-inducing effects. Our previous work showed that these isophthalate derivatives exhibit antiproliferative and elongation-inducing effects in HeLa human cervical cancer cells. In this study we further characterized the effects of bis(3-trifluoromethylbenzyl) 5-(hydroxymethyl)isophthalate (HMI-1a3) on HeLa cell proliferation and morphology. HMI-1a3-induced cell elongation was accompanied with loss of focal adhesions and actin stress fibers, and exposure to HMI-1a3 induced a prominent relocation of cofilin-1 into the nucleus regardless of cell phenotype. The antiproliferative and morphological responses to HMI-1a3 were not modified by coexposure to pharmacological inhibition or activation of PKC, or by RNAi knock-down of specific PKC isoforms, suggesting that the effects of HMI-1a3 were not mediated by PKC. Genome-wide gene expression microarray and gene set enrichment analysis suggested that, among others, HMI-1a3 induces changes in small GTPase-mediated signaling pathways. Our experiments revealed that the isophthalates bind also to the C1 domains of β2-chimaerin, protein kinase D (PKD) and myotonic dystrophy kinase-related Cdc42-binding kinase (MRCK), which are potential mediators of small GTPase signaling and cytoskeletal reorganization. Pharmacological inhibition of MRCK, but not that of PKD attenuated HMI-1a3-induced cell elongation, suggesting that MRCK participates in mediating the effects of HMI-1a3 on HeLa cell morphology. chelerythrine (PubChem CID: 72311); CID755673 (PubChem CID: 755673); Gö6983 (PubChem CID: 3499); phorbol 12,13-dibutyrate (PubChem CID: 37783); phorbol 12-myristate 13-acetate (PubChem CID: CID 27924); U0126 (PubChem CID: 3006531).European journal of pharmaceutical sciences: official journal of the European Federation for Pharmaceutical Sciences 01/2014; 55:46-57. · 2.61 Impact Factor
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ABSTRACT: C1 domains are small zinc-binding structural units of approximately 50 amino acids, originally discovered as lipid-binding modules in protein kinase C (PKC) isoforms. C1 domains that bind and respond to the DAG/phorbol ester are termed as typical, and those that do not respond to DAG/phorbol ester are termed as atypical. To design molecules targeting a specific C1 domain for regulating a specific disease state, it is important to understand the factors that make a C1 domain responsive to DAG/phorbol ester. Here, we determined the volume and surface area of the ligand-binding site for all known C1 domains. No correlation was found between the volume/surface area of ligand-binding site and the DAG/phorbol ester-binding affinity. Solvated molecular dynamics simulation reveals that the presence of water molecules affects the flexibility of the ligand-binding site. Contributions of the binding site residues, their orientations, and the membrane lipids on the responsiveness of a C1 domain towards DAG/phorbol ester have been discussed.Journal of biomolecular Structure & Dynamics 03/2014; · 2.98 Impact Factor