Structural Characterization of an LPA1 Second Extracellular Loop Mimetic with a Self-Assembling Coiled-Coil Folding Constraint.

G protein-coupled receptor (GPCR) structures are of interest as a means to understand biological signal transduction and as tools for therapeutic discovery. The growing number of GPCR crystal structures demonstrates that the extracellular loops (EL) connecting the membrane-spanning helices show tremendous structural variability relative to the more structurally-conserved seven transmembrane α-helical domains. The EL of the LPA(1) receptor have not yet been conclusively resolved, and bear limited sequence identity to known structures.

Structure and catalytic function of sphingosine kinases: analysis by site-directed mutagenesis and enzyme kinetics.

Sphingosine kinases 1 and 2 (SK1 and SK2) generate the bioactive lipid mediator sphingosine 1-phosphate and as such play a significant role in cell fate and in human health and disease. Despite significant interest in and examination of the role played by SK enzymes in disease, comparatively little is currently known about the three-dimensional structure and catalytic mechanisms of these enzymes. To date, limited numbers of studies have used site directed mutagenesis and activity determinations to examine the roles of individual SK residues in substrate, calmodulin, and membrane binding, as well as activation via phosphorylation.

Computational identification and experimental characterization of substrate binding determinants of nucleotide pyrophosphatase/phosphodiesterase 7.

Background: Nucleotide pyrophosphatase/phosphodiesterase 7 (NPP7) is the only member of the mammalian NPP enzyme family that has been confirmed to act as a sphingomyelinase, hydrolyzing sphingomyelin (SM) to form phosphocholine and ceramide. NPP7 additionally hydrolyzes lysophosphatidylcholine (LPC), a substrate preference shared with the NPP2/autotaxin(ATX) and NPP6 mammalian family members. This study utilizes a synergistic combination of molecular modeling validated by experimental site-directed mutagenesis to explore the molecular basis for the unique ability of NPP7 to hydrolyze SM.

Benzyl and naphthalene methylphosphonic acid inhibitors of autotaxin with anti-invasive and anti-metastatic activity.

Autotaxin (ATX, NPP2) is a member of the nucleotide pyrophosphate phosphodiesterase enzyme family. ATX catalyzes the hydrolytic cleavage of lysophosphatidylcholine (LPC) by lysophospholipase D activity, which leads to generation of the growth-factor-like lipid mediator lysophosphatidic acid (LPA). ATX is highly upregulated in metastatic and chemotherapy-resistant carcinomas and represents a potential target to mediate cancer invasion and metastasis.

Pharmacophore development and application toward the identification of novel, small-molecule autotaxin inhibitors.

Autotaxin (ATX) is a secreted glycoprotein with lysophospholipase D (LPLD) activity that generates the bioactive lipid lysophosphatidic acid (LPA) from lysophosphatidylcholine (LPC). Both ATX and LPA have been linked to the promotion and progression of cancer as well as cardiovascular disease and obesity. Despite the fact that ATX inhibitors have the potential to be useful chemotherapeutics for multiple indications, few examples of potent ATX inhibitors are described in the current literature.

Characterization of non-lipid autotaxin inhibitors.

Autotaxin (ATX) is a member of the ecto-nucleotide pyrophosphatase/phosphodiesterase (NPP) family and is a lysophospholipase D that cleaves the choline headgroup from lysophosphatidylcholine to generate the bioactive lipid lysophosphatidic acid (LPA). Enhanced expression of ATX and specific receptors for LPA in numerous cancer cell types has created an interest in studying ATX as a potential chemotherapeutic target. Likewise, ATX has been linked to several additional human diseases including multiple sclerosis, diabetes, obesity, neuropathic pain, and Alzheimer's disease.

Molecular recognition in the sphingosine 1-phosphate receptor family.

Computational modeling and its application in ligand screening and ligand receptor interaction studies play important roles in structure-based drug design. A series of sphingosine 1-phosphate (S1P) receptor ligands with varying potencies and receptor selectivities were docked into homology models of the S1P(1-5) receptors. These studies provided molecular insights into pharmacological trends both across the receptor family as well as at single receptors.

Virtual screening approaches for the identification of non-lipid autotaxin inhibitors.

Autotaxin (ATX, NPP-2) catalyzes the conversion of lysophosphatidyl choline (LPC) to lysophosphatidic acid (LPA), a mitogenic cell survival factor that stimulates cell motility. The high expression of both ATX and receptors for LPA in numerous tumor cell types has produced substantial interest in exploring ATX as an anticancer chemotherapeutic target. ATX inhibitors reported to date are analogs of LPA, a phospholipid, and are more hydrophobic than is typical of orally bioavailable drugs.

Peptide design and structural characterization of a GPCR loop mimetic.

G protein-coupled receptors (GPCRs) control fundamental aspects of human physiology and behaviors. Knowledge of their structures, especially for the loop regions, is limited and has principally been obtained from homology models, mutagenesis data, low resolution structural studies, and high resolution studies of peptide models of receptor segments. We developed an alternate methodology for structurally characterizing GPCR loops, using the human S1P(4) first extracellular loop (E1) as a model system.

A single amino acid determines preference between phospholipids and reveals length restriction for activation of the S1P4 receptor.

Background: Sphingosine-1-phosphate and lysophosphatidic acid (LPA) are ligands for two related families of G protein-coupled receptors, the S1P and LPA receptors, respectively. The lysophospholipid ligands of these receptors are structurally similar, however recognition of these lipids by these receptors is highly selective. A single residue present within the third transmembrane domain (TM) of S1P receptors is thought to determine ligand selectivity; replacement of the naturally occurring glutamic acid with glutamine (present at this position in the LPA receptors) has previously been shown to be sufficient to change the specificity of S1P1 from S1P to 18:1 LPA.