Safety and availability of dapivirine (TMC120) delivered from an intravaginal ring.

Vaginal delivery of 200 mg or 25 mg dapivirine from intravaginal rings (IVRs) was evaluated over a 7-day period in two phase 1 safety trials (IPM001 and IPM008, respectively) in a total of 25 healthy women 19 to 46 years of age. The IVR was generally safe and well tolerated with similar adverse events observed in the placebo and dapivirine groups. Across both studies, dapivirine concentrations in vaginal fluids measured at the introitus, cervix, and ring area were within the mean range of 0.7-7.1 microg/ml. Mean dapivirine concentrations in vaginal and cervical tissues on day 7 were 0.3-0.7 microg/g in IPM001 and 1.5-3.5 microg/g in IPM008. Mean plasma concentrations of dapivirine were <50 pg/ml. Dapivirine from both IVRs was successfully distributed throughout the lower genital tract at concentrations >1000x the EC(50) against wild-type HIV-1 (LAI) in MT4 cells suggesting that IVR delivery of microbicides is a viable option meriting further study.

New insights into human prostacyclin receptor structure and function through natural and synthetic mutations of transmembrane charged residues.

BACKGROUND AND PURPOSE: The human prostacyclin receptor (hIP), a G-protein coupled receptor (GPCR) expressed mainly on platelets and vascular smooth muscle cells, plays important protective roles in the cardiovascular system. We hypothesized that significant insights could be gained into the structure and function of the hIP through mutagenesis of its energetically unfavourably located transmembrane charged residues. EXPERIMENTAL APPROACH: Within its putative transmembrane helices fourteen hydrophilic residues, both unique and conserved across GPCRs, were systematically mutated to assess for effects on receptor structure and function. KEY RESULTS: Mutations of ten of the fourteen charged residues to alanine exhibited defective binding and/or activation. Key potential interactions were identified between 6 core residues; E116(3.49)-R117(3.50) (salt bridge TMIII), D274(7.35)-R279(7.40) (salt bridge TMVII), and D60(2.50)-D288(7.49) (H-bond network TMII-TMVII). Further detailed investigation of E116(3.49) (TMIII) with mutation to a glutamine showed a 2.6-fold increase in agonist-independent basal activity. This increase in activity accounts for a proportion ( approximately 13%) of full agonist induced activation. We further characterized two novel naturally occurring human mutations, R77(2.33)C and R279(7.40)C recently identified in a 1455 human genomic DNA sample screen. The R77(2.33)C variant appeared to exclusively affect expression, while the R279(7.40)C variant, exhibited considerable deficiencies in both agonist binding and activation. CONCLUSIONS AND IMPLICATIONS: Transmembrane charged residues play important roles in maintaining the hIP binding pocket and ensuring normal activation. The critical nature of these charged residues and the presence of naturally occurring mutations have important implications in the rational design of prostacyclin agonists for treating cardiovascular disease.

Microbicides--evaluating multiple formulations of C31G.

Despite a significant worldwide need for effective microbicides to reduce sexually transmitted diseases (STD) and HIV transmission, none is currently available. C31G, a surface active anti-infective agent that is active in vitro against bacterial and viral STD pathogens, was evaluated in a 3-day, once-daily dosing clinical trial designed to assess multiple formulations for safety and acceptance. The trial used a scoring algorithm that was based on relevant subject reported symptoms and signs observed at follow-up. Differences in tolerance and acceptability between the formulations were demonstrated, as was consistency with the results from a previous 7-day trial that involved two of the formulations (1.2% HEC gel, 2.0% N-9). The 1.0% C31G co-polymer gel was the best tolerated, most acceptable formulation, and will be advanced to longer, more comprehensive trials. Thus, formulation differences are relevant to microbicide tolerance and acceptability, and the 3-day trial design validated in this study can be used to assess formulations.

Inhibition of transforming growth factor beta signaling in MCF-7 cells results in resistance to tumor necrosis factor alpha: a role for Bcl-2.

Transforming growth factor beta (TGF-beta) is a multifunctional cytokine capable of regulating diverse cellular processes. In this study we investigated the effect of autocrine TGF-beta signaling on tumor necrosis factor (TNF) alpha-induced cell death. We abrogated the TGF-beta autocrine loop by overexpression of a truncated TGF-beta type II receptor in MCF-7 breast carcinoma cells and found that this generated resistance to TNF-alpha-induced cytotoxicity. To elucidate the molecular basis of the influence of TGF-beta on TNF-alpha-induced cytotoxicity, we evaluated the expression levels or activities of proteins involved in TNF-alpha signal transduction or the regulation of apoptosis in general in TGF-beta-responsive and TGF-beta-nonresponsive MCF-7 cells. We observed no significant difference in the expression of TNF-alpha receptors or the TNF receptor-associated death domain protein. In addition, downstream activation of nuclear factor kappaB by TNF-alpha was not altered in cells that had lost TGF-beta responsiveness. Analysis of members of the Bcl-2 family of apoptosis-regulatory proteins revealed that Bcl-X(L) and Bax expression levels were not changed by disruption of TGF-beta signaling. In contrast, the TGF-beta-nonresponsive cells expressed much higher levels of Bcl-2 protein and mRNA than did cells with an intact TGF-beta autocrine loop. Furthermore, restoration of a TGF-beta signal to MCF-7 cells that had spontaneously acquired resistance to TGF-beta caused a reduction in Bcl-2 protein expression. Taken together, our data indicate that loss of autocrine TGF-beta signaling results in enhanced resistance to TNF-alpha-mediated cell death and that this is likely to be mediated by derepression of Bcl-2 expression.

SecYEG and SecA are the stoichiometric components of preprotein translocase.

The transport of large preproteins across the Escherichia coli plasma membrane is catalyzed by preprotein translocase, comprised of the peripherally bound SecA subunit and an integrally bound heterotrimeric domain consisting of the SecY, SecE, and SecG subunits. We have now placed the secY, secE, and secG genes under the control of an arabinose-inducible promoter on a multicopy plasmid. Upon induction, all three of the proteins are strongly overexpressed and recovered in the plasma membrane fraction. These membranes show a strong enhancement of 1) translocation ATPase activity, 2) preprotein translocation, 3) capacity for SecA binding, and 4) formation of the membrane-inserted form of SecA. These data establish that SecY, SecE, and SecG constitute the integral membrane domain of preprotein translocase.

Band 1 subunit of Escherichia coli preportein translocase and integral membrane export factor P12 are the same protein.

Escherichia coli preprotein translocase consists of the peripheral membrane protein SecA and the integral membrane domain SecY/E. SecY/E, whether isolated chromatographically or by immunoprecipitation, was found to be complex of three polypeptides, SecY, SecE, and band 1. Band 1 did not correspond to a known sec gene product. The independent purification of the separate integral membrane polypeptides needed for reconstitution of translocation yielded SecY, SecE, and a protein that we termed P12. Based on the sequence of P12, we have prepared antisera to a carboxyl-terminal peptide domain and shown that this antiserum specifically labels only P12 on immunoblots of inner membrane vesicles. We now report that affinity-purified anti-P12 antibodies specifically label the band 1 subunit of the SecY/E complex, whether the SecY/E was isolated chromatographically or by precipitation with antibodies to an epitope-tagged SecY subunit. In addition, the antiserum to P12 can specifically immunoprecipitate the full three-subunit SecY/E complex from detergent extracts. This finding completes the identification of the polypeptides that are essential for catalysis of preprotein translocation.

Association of the Mr 58,000 postsynaptic protein of electric tissue with Torpedo dystrophin and the Mr 87,000 postsynaptic protein.

Dystrophin was purified by immunoaffinity chromatography from detergent-solubilized Torpedo electric organ postsynaptic membranes using monoclonal antibodies. A major doublet of proteins at Mr 58,000 and minor proteins at Mr 87,000, Mr 45,000, and Mr 30,000 reproducibly copurified with dystrophin. The Mr 58,000 and Mr 87,000 proteins were identical to previously described peripheral membrane proteins (Mr 58,000 protein and 87,000 protein) whose muscle homologs are associated with the sarcolemma (Froehner, S. C., Murnane, A. A., Tobler, M., Peng, H. B., and Sealock, R. (1987) J. Cell Biol. 104, 1633-1646; Carr, C., Fischbach, G. D., and Cohen, J. B. (1989) J. Cell Biol. 109, 1753-1764). The copurification of dystrophin and Mr 58,000 protein was shown to be specific, since dystrophin was also captured with a monoclonal antibody against the Mr 58,000 protein but not by several control antibodies. The Mr 87,000 protein was a major component (along with the Mr 58,000 protein) in material purified on anti-58,000 columns, suggesting that the Mr 58,000 protein forms a distinct complex with the Mr 87,000 protein, as well as with dystrophin. Immunofluorescence staining of skeletal and cardiac muscle from the dystrophin-minus mdx mouse with the anti-58,000 antibody was confined to the sarcolemma as in normal muscle but was much reduced in intensity, even though immunoblotting demonstrated that the contents of Mr 58,000 protein in normal and mdx muscle were comparable. Thus, the Mr 58,000 protein appears to associate inefficiently with the sarcolemmal membrane in the absence of dystrophin. This deficiency may contribute to the membrane abnormalities that lead to muscle necrosis in dystrophic muscle.

Localization of dystrophin relative to acetylcholine receptor domains in electric tissue and adult and cultured skeletal muscle.

Two high-affinity mAbs were prepared against Torpedo dystrophin, an electric organ protein that is closely similar to human dystrophin, the gene product of the Duchenne muscular dystrophy locus. The antibodies were used to localize dystrophin relative to acetylcholine receptors (AChR) in electric organ and in skeletal muscle, and to show identity between Torpedo dystrophin and the previously described 270/300-kD Torpedo postsynaptic protein. Dystrophin was found in both AChR-rich and AChR-poor regions of the innervated face of the electroplaque. Immunogold experiments showed that AChR and dystrophin were closely intermingled in the AChR domains. In contrast, dystrophin appeared to be absent from many or all AChR-rich domains of the rat neuromuscular junction and of AChR clusters in cultured muscle (Xenopus laevis). It was present, however, in the immediately surrounding membrane (deep regions of the junctional folds, membrane domains interdigitating with and surrounding AChR domains within clusters). These results suggest that dystrophin may have a role in organization of AChR in electric tissue. Dystrophin is not, however, an obligatory component of AChR domains in muscle and, at the neuromuscular junction, its roles may be more related to organization of the junctional folds.

Monoclonal antibodies to cytoplasmic domains of the acetylcholine receptor.

Fourteen clonal hybridoma lines that secrete monoclonal antibodies (mabs) to the Torpedo acetylcholine receptor (AChR) have been isolated. When analyzed by an immunoreplica technique, two mabs recognized the alpha subunit, three reacted with the beta subunit, one reacted with the gamma chain, and five recognized the delta subunit. One mab failed to react with any of the subunits using this assay and two mabs recognized determinants found on both the gamma and the delta subunits. These were classified according to their reactivities with the membrane-bound Torpedo AChR. One category is comprised of mabs (including both anti-alpha mabs) that recognize extracellular epitopes. A second classification included mabs that are unable to bind the membrane-associated AChR. The third category is comprised of mabs directed against cytoplasmic epitopes of the AChR. The latter mabs, all of which recognize the gamma or delta subunits or both, bind only slightly to sealed, outside-out Torpedo vesicles. The binding is increased 10-20-fold by either alkaline extraction or treatment of the vesicles with 10 mM lithium diiodosalicylate but not by permeabilization of the vesicles with saponin. Three of the six mabs in this category react with frog muscle endplates but only if the cytoplasmic surface of the membrane is accessible.