Structural and functional characterization of the conserved salt bridge in mammalian Paneth cell alpha-defensins - Solution structures of mouse cryptdin-4 AND (E15D)-cryptdin-4

Defensins are mediators of mammalian innate immunity, and knowledge of their structure-function relationships is essential for understanding their mechanisms of action. We report here the NMR solution structures of the mouse Paneth cell α-defensin cryptdin-4 (Crp4) and a mutant (E15D)-Crp4 peptide, in which a conserved Glu15 residue was replaced by Asp. Structural analysis of the two peptides confirms the involvement of this Glu in a conserved salt bridge that is removed in the mutant because of the shortened side chain. Despite disruption of this structural feature, the peptide variant retains a well defined native fold because of a rearrangement of side chains, which result in compensating favorable interactions. Furthermore, salt bridge-deficient Crp4 mutants were tested for bactericidal effects and resistance to proteolytic degradation, and all of the variants had similar bactericidal activities and stability to proteolysis. These findings support the conclusion that the function of the conserved salt bridge in Crp4 is not linked to bactericidal activity or proteolytic stability of the mature peptide.

Cinderella no longer: alpha-catenin steps out of cadherin's shadow

To date, alpha-catenin has been best understood as an important cytoplasmic component of the classical cadherin complex responsible for cell-cell adhesion. By virtue of its capacity to bind F-actin, alpha-catenin was commonly envisaged to support cadherin function by coupling the adhesion receptor to the actin cytoskeleton. But is alpha-catenin solely the cadherin's handmaiden? A range of recent developments suggest, instead, that its biological activity is much more complex than previously appreciated. Evidence from cellular systems and model organisms demonstrates a clear, often dramatic, role for alpha-catenin in tissue organization and morphogenesis. The morphogenetic impact of alpha-catenin reflects its capacity to mediate functional cooperation between cadherins and the actin cytoskeleton, but is not confined to this. alpha-Catenin has a role in regulating cell proliferation and cadherin-independent pools of alpha-catenin may contribute to its functional impact.

Halofenate is a selective peroxisome proliferator-activated receptor gamma modulator with antidiabetic activity

Halofenate has been shown previously to lower triglycerides in dyslipidemic subjects. In addition, significant decreases in fasting plasma glucose were observed but only in type 2 diabetic patients. We hypothesized that halofenate might be an insulin sensitizer, and we present data to suggest that halofenate is a selective peroxisome proliferator-activated receptor (PPAR)-gamma modulator (SPPAR gamma M). We demonstrate that the circulating form of halofenate, halofenic acid (HA), binds to and selectively modulates PPAR-gamma. Reporter assays show that HA is a partial PPAR-gamma agonist, which can antagonize the activity of the full agonist rosiglitazone. The data suggest that the partial agonism of RA may be explained in part by effective displacement of corepressors (N-CoR and SMRT) coupled with inefficient recruitment of coactivators (p300, CBP, and TRAP 220). In human preadipocytes, HA displays weak adipogenic activity and antagonizes rosiglitazone-mediated adipogenic differentiation. Moreover, in 3T3-L1 adipocytes, HA selectively modulates the expression of multiple PPAR-gamma-responsive genes. Studies in the diabetic ob/ob mouse demonstrate halofenate's acute antidiabetic properties. Longer-term studies in the obese Zucker (fa/fa) rat demonstrate halofenate's comparable insulin sensitization to rosiglitazone in the absence of body weight increases. Our data establish halofenate as a novel SPPAR-gamma M with promising therapeutic utility with the potential for less weight gain.

Design, Synthesis, Potency and Cytoselectivity of Anticancer Agents Derived by Parallel Synthesis from alpha-Aminosuberic Acid

Chemotherapy in the last century was characterized by cytotoxic drugs that did not discriminate between cancerous and normal cell types and were consequently accompanied by toxic side effects that were often dose limiting. The ability of differentiating agents to selectively kill cancer cells or transform them to a nonproliferating or normal phenotype could lead to cell- and tissue-specific drugs without the side effects of current cancer chemotherapeutics. This may be possible for a new generation of histone deacetylase inhibitors derived from amino acids. Structure-activity relationships are now reported for 43 compounds derived from 2-aminosuberic acid that kill a range of cancer cells, 26 being potent cytotoxins against MM96L melanoma cells (IC50 20 nM-1 mu M), while 17 were between 5- and 60-fold more selective in killing MM96L melanoma cells versus normal (neonatal foreskin fibroblasts, NFF) cells. This represents a 10- to 100-fold increase in potency and up to a 10-fold higher selectivity over previously reported compounds derived from cysteine (J. Med. Chem. 2004, 47, 2984). Selectivity is also an underestimate, because the normal cells, NFF, are rarely all killed by the drugs that also induce selective blockade of the cell cycle for normal but not cancer cells. Selected compounds were tested against a panel of human cancer cell lines (melanomas, prostate, breast, ovarian, cervical, lung, and colon) and found to be both selective and potent cytotoxins (IC50 20 nM-1 mu M). Compounds in this class typically inhibit human histone deacetylases, as evidenced by hyperacetylation of histones in both normal and cancer cells, induce expression of p21, and differentiate surviving cancer cells to a nonproliferating phenotype. These compounds may be valuable leads for the development of new chemotherapeutic agents.