Current Research and Scholarly Interests
My laboratory of molecular and cellular immunology is interested in mechanisms of T cell anergy and the pathophysiology and immunotherapy of preclinical animal models of autoimmune disease.
I. T Cell Anergy: We have identified a ubiquitin E3 ligase (GRAIL) that seems to be central to the control of T cell anergy. We developed a novel prokaryotic system to screen for E3 ligase substrates and identified RhoGDI as an E3 substrate of GRAIL. Using two-hybrid technology to identify proteins that bound the lumenal or extracellular domain of GRAIL identified CD151, a member of the tetraspanin family of membrane proteins and GRAIL over-expression promoted polyubiquitination of all tested tetraspanins. These findings identify for the first time an E3 ligase with a substrate-binding domain spatially restricted by a membrane from its ubiquitination machinery. Recent studies focus on understanding GRAIL mediated CD4 T cell unresponsiveness. Two deubiquiting enzyes, USP8 and OTUB1, play contrasting roles in maintaining GRAIL stability
II. Gene Therapy: We have demonstrated that the local delivery of anti-inflammatory proteins via adoptive cellular gene therapy using syngeneic dendritic cells (DCs) transduced to express immunoregulatory proteins, in three murine models of autoimmunity (RA, MS and T1D), provide therapeutic effect both in the prevention of disease onset and in therapy of established disease.
III. Gene expression studies in autoimmunity: The major emphasis placed on disease associated genetic mutations or polymorphisms to understand the genetics of T1D has failed to advance either understanding of T1D pathogenesis or to identify therapeutic targets. Recent studies from my lab have demonstrated that tissue- and disease-specific changes in mRNA expression, rather than DNA variants, may underlie the progression of T1D. By combining the expertise of the lab in T1D research with established preclinical models and patient samples/tissues from the Network for Pancreatic Organ Donors with Diabetes, nPOD (http://www.jdrfnpod.org/), my lab has both demonstrated a potential defect in peripheral tolerance in NOD mice that has homologies in T1D patients and have demonstrated that appropriate immunotherapy may overcome this defect.
iv. Mechanism of action of biologic therapy: Our inability to identify subgroups of RA patients who will or will not respond to a biologic therapy is frustrating to clinicians and patients and a major burden to the health care economy. My lab is currently employing new multiplexed technologies in proteomic and genomic analysis of the response of patients PBCs to activation with one of the cytokines (TNF) thought to be a major pathophysiological component of RA. By analyzing the response of RA patient PBCs to TNF [using gene expression of PBCs by microarray technology and algorithms recently developed at Stanford that allow total PBC gene expression to be deconvoluted to know which cell subset expressed which subset of genes, and the new cytometry time of flight (CyTOF) proteomic technology developed in Garry Nolans lab at Stanford], we hope to dissect the individual patients PBC gene expression or protein modification pattern in response to TNF activation to identify responders from non-responders to TNF inhibitor therapies; commercially available and FDA approved therapeutics