Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

My previous discovery grant in 2007-2012 was on insulin-like growth factor (IGF)-I, which we and others using conditional knockouts have established as essential for embryonic development, postnatal growth, and maturation of major organ systems. Within the pancreatic islets, it promotes β-cell proliferation and survival. In order to explore novel targets of its action, we performed a whole-genome cDNA microarray analysis on isolated islets from mice overexpressing IGF-I, and found 82 genes specifically up- or down-regulated. Prominent amongst which was CCN5/WISP2 , previously not known to be either expressed in the pancreatic β-cells or induced by IGF-I. CCN or WISP represents a family of six cysteine-rich, glycosylated proteins known to be involved in cell adhesion and extracellular matrix (ECM) remodeling, and cell proliferation. Another isoform, CCN2/CTGF, has already been established to play an essential role in the embryonic development of pancreatic islets. On the other hand, ectopic expression of Wnt1 dramatically induces CCN5 expression, supporting a co-regulation by both Wnt1 and IGF-I on the control of β-cell proliferation and survival through CCN5 production.

In order to assess the function of CCN5, we showed that its overexpression and treatment using recombinant protein (rCCN5) accelerated the proliferation of murine insulinoma cells, at least in part by activating Akt kinase and cyclin D1. We thus hypothesize that increased CCN5 production promotes β-cell proliferation and regeneration. To further characterize its pro-islet properties, we propose to 1) establish in vitro stimulation of CCN5 on the proliferation of the pancreatic islets. Freshly isolated murine islets will be stimulated by rCCN5, IGF-I or vehicle; cell proliferation will be measured by MTT assay, BrdU or EdU incorporation; and supported by Akt and Erk1/2 phosphorylation, as well as the increases in cyclin D1 and CDK4 levels; 2) establish β-cell specific CCN5 gene deletion and assess possible decreases in β-cell mass, β-cell proliferation and changes in insulin secretion and glucose homeostasis; and 3) characterize a putative cell surface receptor, ChrnA3, identified through TriCEPS-based ligand-receptor capture.

Findings from this proposal will significantly contribute to uncover CCN5 as a novel physiological regulator of pancreatic β-cell proliferation, a cell surface receptor and intracellular signaling pathways mediating its actions, in the next 5 yr. In the meantime, we have also been supported by CIHR and Canadian Diabetes Association on the anti-diabetic properties of Reg family proteins. With renewed funding expected from NSERC and CIHR, my longer-term goal is to characterize the biological roles of novel growth factors that our body use to control normal glucose homeostasis and develop pharmaceutical interventions in order to prevent or cure diabetes mellitus.