Single Cell Dynamics of the White/Opaque Epigenetic Switch in Candida albicans
Matthew Bennett, Rice University, *Michael Gustin, Rice University, Kresimir Josic, University of Houston
Aldose reductase (ALR2) has recently been shown to be an important mediator of colon cancer signaling pathways. The reduction of glutathione (GS-) conjugated aldehydes by ALR2 produces intermediates that are involved in inflammation and cancer-signaling pathways. Although ALR2 inhibitors have been shown to arrest tumor growth in mice, the majority have failed in clinical trials due to undesirable side effects. It is likely that a portion of the observed side effects were due to cellular toxicity resulting from indiscriminate inhibition of GS-aldehyde reduction as well as non-GS-conjugated aldehyde reduction. Analysis of our crystal structure of ALR2 with a bound GS-aldehyde analog revealed a GS-binding site separate from the catalytic site implying that one could develop selective inhibitors of the GS-binding site, which would alleviate GS-aldehyde reduction and subsequent cancer signaling, while still allowing aliphatic aldehyde reduction and thus reducing associated side effects.
Clustering analyses performed on the ~ 100 ALR2 structures in the Protein Data Bank (PDB) revealed three primary "conformations" in the GS-binding site. Docking studies utilizing the AUTODOCK Vina program and the Directory of Useful Decoys (DUD) ALR2 database of known binders/decoys revealed that by docking to representatives from each of the conformations represented in the PDB, and developing a composite ranking of combined energy scores, early discrimination of known ALR2 binders was near ideal. Additionally, testing of the top compounds from the composite ranking revealed two previously unidentified ALR2 inhibitors.
Gold Nanoparticle Cancer Therapeutics: A Tale of Two Projects
*Rebekah Drezek, PhD, Rice University, Liz Bikram, University of Houston
In this seminar, we highlight results from two collaborative Dunn awards focused on development of gold nanoparticle cancer therapeutics. Both projects addressed the critical need for new technologies for more specifically targeting cancer therapies. The first project investigated the use of T cells as Trojan horse delivery vehicles for gold nanoparticle mediated photothermal cancer therapy. The second project investigated a novel strategy to potentially mask the presence of a drug carried on a gold nanoparticle platform until activation of the complex by a mRNA binding event. In telling the stories of these two projects, we will also share lessons learned about collaborative research and moving forward science both when experiments work as expected and when they do not.
Structure Determination of Novel Targets Identified from a Multi-Drug Resistant Pathogen
*Yousif Shamoo, Rice University, *Cesar Arias, University of Texas Health Science Center at Houston
With over 350,000 hospital-acquired antibiotic resistant infections per year and an estimated cost expected to exceed $17 billion in the U.S. alone, there is a clear need for new antimicrobial agents, as well as novel strategies to extend their clinical efficacy. A group of six organisms, collectively known as the ‘ESKAPE’ pathogens, have been singled out by the Infectious Disease Society of America as highly problematic for the medical community a list that includes enterococci. The antibiotic daptomycin (DAP) is frequently used as an antibiotic of last resort for enterococci infections in patients. Unfortunately, cases of resistance to DAP by both Enterococcus faecium and E. faecalis have already been reported clinically. The investigators, Dr. Cesar Arias and Dr. Yousif Shamoo have identified the genetic changes associated with daptomycin resistance and used this information to determine the biochemical mechanisms of resistance by this important hospital pathogen. The goal of the project was to identify the mechanisms of resistance and work to identify suitable drug targets for future development. The molecular mechanisms that produce daptomycin resistance in the pathogen Enterococcus faecalis follow a clear order and hierarchy of genetic changes. The predominant evolutionary trajectory to resistance include changes to the bacterial membrane through a series of genes that encode proteins that are part of the cell’s stress response network and through changes to cardiolipin synthase (cls) a protein that also mediates the composition of the bacterial membrane. We have gone on to isolate these proteins and elucidate how changes in their structure and function lead to resistance. By understanding how cells respond and become resistant to antibiotics we can provide important insights for the development of drugs that can hinder the rise to resistance and increase the effectiveness of current and future antibiotics.
*Denotes presenting authors.