Cd36, a class B scavenger receptor, functions as a monomer to bind acetylated and oxidized low-density lipoproteins

Cd36 is a small-molecular-weight integral membrane protein expressed in a diverse, but select, range of cell types. It has an equally diverse range of ligands and physiological functions, which has implicated Cd36 in a number of diseases including insulin resistance, diabetes, and, most notably, atherosclerosis. The protein is reported to reside in detergent-resistant microdomains within the plasma membrane and to form homo- and hetero-intermolecular interactions. These data suggest that this class B scavenger receptor may gain functionality for ligand binding, and/or ligand internalization, by formation of protein complexes at the cell surface. Here, we have overexpressed Cd36 in insect cells, purified the recombinant protein to homogeneity, and analyzed its stability and solubility in a variety of nonionic and zwitterionic detergents. Octylglucoside conferred the greatest degree of stability, and by analytical ultracentrifugation we show that the protein is monomeric. A solid-phase ligand-binding assay demonstrated that the purified monomeric protein retains high affinity for acetylated and oxidized low-density lipoproteins. Therefore, no accessory proteins are required for interaction with ligand, and binding is a property of the monomeric fold of the protein. Thus, the highly purified and functional Cd36 should be suitable for crystallization in octylglucoside, and the in vitro ligand-binding assay represents a promising screen for identification of bioactive molecules targeting atherogenesis at the level of ligand binding.     

Design and synthesis of quinolin-2(1H)-one derivatives as potent CDK5 inhibitors

Cyclin-dependent kinase 5 (CDK5) is a serine/threonine protein kinase and its deregulation is implicated in a number of neurodegenerative disorders such as Alzheimer's disease, amyotrophic lateral sclerosis, and ischemic stroke. Using active site homology modeling between CDK5 and CDK2, we explored several different chemical series of potent CDK5 inhibitors. In this report, we describe the design, synthesis, and CDK5 inhibitory activities of quinolin-2(1H)-one derivatives.     

The insulin and EGF receptor structures: new insights into ligand-induced receptor activation

The insulin receptor (IR) and epidermal growth factor receptor (EGFR; also known as ErbB) families exhibit similarities in the composition of their ectodomains. The past five years have seen structures determined for all members of the EGFR family including some complexes with ligand or monoclonal antibody fragments. These structures have led to a clearer understanding of their mechanism of activation and inhibition. By contrast, obtaining equivalent understanding of the IR family has lagged behind. However, within the past year, structures of partial and complete ectodomains of the IR have been published that show that the extracellular region of the receptor adopts an unexpected 'inverted V' conformation relative to the cell membrane. This is very different from the folded-over (tethered) conformation of the unactivated EGFR and provides insight into the potential mechanism of activation of the IR.     

Inhibition of mycobacterial arylamine N-acetyltransferase contributes to anti-mycobacterial activity of Warburgia salutaris

In this study, we show that extracts and a purified compound of Warburgia salutaris exhibit anti-mycobacterial activity against Mycobacterium tuberculosis H37Rv and Mycobacterium bovis BCG Pasteur. The extracts did not inhibit growth of Escherichia coli and were not toxic to cultured mammalian macrophage cells at the concentrations at which anti-mycobacterial activity was observed. The extract and pure compound inhibited pure recombinant arylamine N-acetyltransferase (NAT), an enzyme involved in mycobacterial cell wall lipid synthesis. Moreover, neither extract nor pure compound inhibited growth of a strain of M. bovis BCG in which nat has been deleted suggesting that NAT may indeed be a target within the mycobacterial cell. The purified compound is a novel drimane sesquiterpenoid lactone, 11alpha-hydroxycinnamosmolide. These studies show that W. salutaris is a useful source of anti-tubercular compounds for further analysis and supports the hypothesis of a link between NAT inhibition and anti-mycobacterial activity.     

Novel tetrahydroisoquinolines are histamine H3 antagonists and serotonin reuptake inhibitors

A series of novel 4-aryl-1,2,3,4-tetrahydroisoquinoline-based histamine H(3) ligands that also have serotonin reuptake transporter inhibitor activity is described. The synthesis, in vitro biological data, and select pharmacokinetic data for these novel compounds are discussed.     

4-[6-(2-Aminoethyl)naphthalen-2-yl]benzonitriles are potent histamine H3 receptor antagonists with high CNS penetration

4-[6-(2-Tertiaryaminoethyl)naphthalen-2-yl]benzonitriles are conformationally constrained histamine H3 receptor antagonists with high potency and selectivity. The analogs were designed around a naphthalene core, with the goal of enhancing lipophilicity and CNS penetration, as compared to a previously reported benzofuran series. The SAR of the tertiary amine moiety is similar to that reported for the benzofuran series, with analogs bearing a 2-methylpyrrolidine substituent possessing the greatest rat and human H3 receptor binding affinities.     

PDE-10A inhibitors as insulin secretagogues

Modulation of cAMP levels has been linked to insulin secretion in preclinical animal models and in humans. The high expression of PDE-10A in pancreatic islets suggested that inhibition of this enzyme may provide the necessary modulation to elicit increased insulin secretion. Using an HTS approach, we have identified quinoline-based PDE-10A inhibitors as insulin secretagogues in vitro. Optimized compounds were evaluated in vivo where improvements in glucose tolerance and increases in insulin secretion were measured.     

The protein kinase C orthologue PkcA plays a role in cell wall integrity and polarized growth in Aspergillus nidulans

The calC2 mutation in Aspergillus nidulans causes hypersensitivity to Calcofluor White, along with other drug sensitivities that indicate a defect in cell wall integrity. We have cloned CalC by complementation, isolating the A. nidulans orthologue of protein kinase C (PkcA). The pkcA allele of the calC2 strain contains a mutation predicted to introduce a charged arginine residue in place of neutral glycine at a conserved site located immediately beside the C1B regulatory domain. Both PkcA and calC2 map to the same region of chromosome VIII. A PkcA::GFP chimera localizes to hyphal apices and growing septa, as well as to the conidiogenous apices of phialides, indicating a role for PkcA in polarized cell wall growth. These observations support the hypothesis that the role of PkcA in A. nidulans, is comparable to that played by Pkc1p in the Saccharomyces cerevisiae cell wall integrity pathway.