Ioana A. Rus

Ioana A. Rus
B.S. University of North Carolina, 2007
M.S. Mount Sinai School of Medicine, 2009Image: Ioana A. Rus

6th Year MSTP
4th Year Genetics Graduate Student

Advisor: Nicholas Tonks, PhD

Cold Spring Harbor Laboratory

Graduate Program: Genetics

Title: Structural & Physological Studies with Conformation-Sensor Antibodies to Oxidized PTP1B

Abstract: 

Protein tyrosine phosphatase 1B (PTP1B) is an important regulator of signaling by the insulin and leptin receptors and has been a prized target in the pharmaceutical industry for therapeutic intervention in type II diabetes and obesity. Initially it was observed that PTP1B-null mice fed a high-fat diet remained healthy and did not develop type 2 diabetes or obesity. Therefore, inhibition of PTP1B is an attractive potential therapy for patients suffering from diabetes and obesity. There has been a considerable effort in developing potent inhibitors of PTP1B, particularly focused on the active site pocket. However, the discovery of pharmaceutically acceptable inhibitors directed to the active site of PTP1B remains elusive. Potent and highly specific small molecule inhibitors to PTP1B have been reported on the basis of in vitro studies, however they are charged and poorly bioavailable. PTP1B activity is regulated at multiple levels, including reversible inactivation due to transient oxidation by reactive oxygen species (ROS) produced in response to insulin. The conformation and activity of PTP1B depend on the redox status of the catalytic cysteine, which undergoes oxidation to form a cyclic sulphenamide intermediate to induce a profound conformational change at the active site that renders the enzyme inactive. Stabilization of the inactivated, oxidized conformation of PTP1B (PTP1Box) by single chain antibodies (scFvs) directed against oxidation-specific epitopes has been demonstrated in the Tonks lab as an alternative means to inhibit the activity of PTP1B and to manipulate its regulatory effect in signaling. The interaction between these conformation-specific antibodies and PTP1B-OX has been characterized in vitro and in vivo. One scFv (scFv45) was selected for further analysis and has been shown to stabilize and sequester the oxidized and inactivated form of PTP1B in response to insulin stimulation when expressed in mammalian cells as an intracellular antibody (intrabody). These scFvs demonstrate proof of principle that stabilizing PTP1Box may provide an alternative strategy to inhibit PTP1B and manipulate its signaling role in pathophysiological conditions. We aim to use scFv45 for structural studies to determine the binding interface with PTP1B by X-ray crystallography in collaboration with Leemor Joshua-Tor at Cold Spring Harbor Laboratory and by site directed mutagenesis. These studies will define the interface in molecular detail and will subsequently be used to direct the search for small molecules that mimic the effect of scFv45 on PTP1Box. Such small molecules that stabilize the oxidized, inactive form of PTP1B would provide a novel avenue to inhibit its enzymatic activity, and would constitute a potential clinical treatment for type 2 diabetes and obesity.

Publications:
(pre-MSTP publications indicated with an *)

*Vijayakumar S, Liu G, Rus IA, Yao S, Chen Y, Akiri G, Grumolato L, Aaronson SA. (2011). High-Frequency Canonical Wnt Activation in Multiple Sarcoma Subtypes Drives Proliferation through a TCF/ß-Catenin Target Gene, CDC25A. Cancer Cell. 19(5):601-12.

*Geer CB, Stasko NA, Rus IA, Lord ST, Schoenfisch MH. Influence of glutathione and its derivatives on fibrin polymerization. Biomacromolecules. 2008 Jul;9(7):1876-82. 

*Geer CB, Rus IA, Lord ST, Schoenfisch MH. Surface-dependent fibrinopeptide A accessibility to thrombin. Acta Biomater. 2007 Sep;3(5):663-8.