Notice Board

The Alberta RNA Research and Training Institute present Dr. Harmen Steele and Michelle Nemetchek, a postdoctoral fellow and graduate student from the University of Montana.

Nemetchek will be presenting “Mechanisms of Biased Agonism in the Nuclear Receptor PPARγ” and Steele will be presenting “The Human Cytochrome c Domain-Swapped Dimer: Tighter Regulation of Intrinsic Apoptosis”. The ARRTI Speaker Series is open to the public and was established to bring leading researchers to the University of Lethbridge for lectures on a broad range of topics relating to RNA research.

All are welcome! Coffee and snacks will be provided!

The ARRTI Speaker Series is sponsored by the RNA Salon initiative of the RNA Society, with additional support from Lexogen.

Michelle Nemetchek: Mechanisms of Biased Agonism in the Nuclear Receptor PPARγ

PPARγ is a nuclear receptor and a target of many FDA-approved type II diabetes drugs. These prescription drugs re-sensitize patients to insulin, and are commonly prescribed alone or alongside other antidiabetic drugs such as metformin. However, PPARγ signaling upon binding of strong agonists also causes adverse side effects such as bone fractures, weight gain, and organ failure. Surprisingly, partial and non-agonists of PPARγ do not activate this pathway but still induce anti-diabetic effects with reduced side effects. It is unclear how these drugs remain potent anti-diabetics with little canonical pathway activation.

We hypothesize that certain drugs cause PPARγ to signal via novel pathways in addition to the canonical pathway and that the relative signaling intensity varies depending on the drug. This phenomenon is known as biased agonism. I  examine the structural mechanism of biased agonism in PPARγ through analysis of binding through two different surfaces of PPARγ: the heterodimerization surface, where PPARγ interacts with the nuclear receptor RxRα; and the coregulator surface, through which PPARγ interacts with proteins that either interact with RNA polymerase or directly affect chromatin structure through histone modification. Certain drugs affect PPARγ interaction with these other partners in a unique manner, showing "bias" towards certain partners. To this end, we use Nuclear Magnetic Resonance, Förster Resonance Energy Transfer, Fluorescence Anisotropy, and other methods to demonstrate changes in PPARγ structure that lead to these interactions. Through biophysical and biochemical analysis, I aim to provide a structural basis for different kinds of signaling through PPARγ which will aid in rational drug design of biased agonists.

Dr. Harmen Steele: The Human Cytochrome c Domain-Swapped Dimer: Tighter Regulation of Intrinsic Apoptosis

The heme protein Cytochrome c (cytc) plays a crucial role in the electron transport chain, has been used as a model protein to study protein folding, and more recently has been determined to play a role in initiating apoptosis. Cytc’s interaction with the lipid cardiolipin results in initiation of intrinsic apoptosis when, among other things, the oxidation of CL by cytc increases permeabilization of the mitochondrial membrane.  The results of this membrane permeabilization is the releasees of various proapoptotic factors from the mitochondria including cytc. A domain-swapped dimer (DSD) conformation of cytc from various species have been published by various labs, including the Bowler lab. We postulate that the DSD conformation is a governor or switch that has evolved to allow tighter control over apoptosis. The kinetic stability of the DSD will be present for multiple species hypothesizing that the human DSD has evolved to be stable enough for biological function.  The interaction with cardiolipin and structural dynamics will be studied using fluorescence correlation spectroscopy, fluorescence anisotropy, circular dichroism, and computer modeling.  The data presented will show that the DSD is in a highly competent position for increased and efficient peroxidase of cardiolipin.  Data looking at the functional peroxidase activity will be presented to show that not only is the conformation ideal for peroxidase, there is a dramatic enhancement of Cytochrome c’s activity in the DSD conformation.