The SIRP:CD47 Signaling Pathway in Pancreatic Beta-Cell Survival”
Contact PI: Robert Sharp, PhD, University of Florida
Start Date: March 2021
Our proposed project entitled, “The SIRP:CD47 Signaling Pathway in Pancreatic β-Cell Survival,” will examine the signal regulatory protein (SIRP) family of receptors, which consists of SIRPα and SIRPγ, and their binding partner CD47, also known as integrin associated protein (IAP). The SIRP:CD47 signaling pathway have been suggested to serve an immunoregulatory role in CD8+ T cells and NK cells, and to promote insulin production and survival among β-cells. Hence, the SIRP:CD47 axis has many potential points of intersection in T1D research, but the precise role for SIRP:CD47 signaling in T1D development has not yet been characterized. The overall goal of the proposed project is to characterize the functional consequences of SIRP:CD47 pathway signaling in human immune cells and islet β-cells and to determine the clinical significance of two T1D risk-associated single nucleotide polymorphisms (SNPs) tagged to SIRPG (rs2281808 and rs6043409). We will characterize SIRPα, SIRPγ, and CD47 expression levels on peripheral blood mononuclear cells (PBMCs) and paraffin embedded human pancreatic tissues from individuals with T1D and rare at-risk subjects, who are positive for islet autoantibodies (AAb) but do not have diabetes, as compared to no-diabetes controls. We will then explore the functional impact of SIRP:CD47 signaling on in vitro β-cell killing. To do this, we will generate SIRPγ/CD47 knock out clones, SIRPγ/CD47 enhanced expression clones, and SNP-edited clones of CD8+ T cell avatars (expressing an IGRP-reactive T cell receptor), NK cells, and a human β-cell line. Our goal, is to better understand the mechanisms involved in immunoregulation and β-cell survival, and how these are breached in T1D pathogenesis. The SIRP/CD47 pathway represents a new area for investigation alongside other established T1D-associated immunoregulatory pathways (e.g., CD28/CTLA-4, CD226/TIGIT). Our future goal is to extend these studies beyond the cell culture dish to the three-dimensional microphysiological system (3D MPS) known as the islet-immune Chip (iiChip) that is currently under development at the University of Florida with funding from the HIRN Consortium on Human Islet Biomimetics (CHIB). Ultimately, using this isogenic “disease-on-a-chip” model, we can precisely determine the mechanisms for cell-mediated β-cell destruction and immunoregulation based upon SIRP/CD47 signaling in both immune and islet cells as it pertains to T1D.