Oral Presentation Australian Diabetes Society and the Australian Diabetes Educators Association Annual Scientific Meeting 2017

Control of insulin secretion by integrin-basement membrane protein interactions (#101)

Wan Jun Gan 1 , Oanh Hoang Do 1 , Elena Kosobrodova 2 , Marcela Bilek 2 , Peter P Thorn 1
  1. Charles Perkins Center, University of Sydney, Camperdown, NSW, Australia
  2. School of Physics , University of Sydney, Camperdown, NSW, Australia

Cell-based therapies such as islet transplantation or engineering of stem cells, to restore insulin secretion, are promising treatments for type-1 diabetic patients. However, these cells secrete less insulin than native beta cells. Our recent work, in intact islets, shows that beta cells are structurally polarised and insulin secretion is selectively targeted towards the vasculature (1,2). One of the factors that might regulate this targeting is the extracellular matrix. Here we test the hypothesis that extracellular matrixs, secreted by vascular endothelial cells, induce integrin responses in the beta cells. These integrins form focal adhesions which provide an important cue for beta cell orientation.

 Consistent with this hypothesis we show that, in intact islets, focal adhesion proteins such as talin and phosphorylated paxillin are enriched along the vascular face of the beta cell. We screened for effects of matrix substrates (laminin, fibronectin and collagenIV) by plating dispersed beta cells onto coated coverslips. Staining of focal adhesion proteins shows selectively enrichment at the contact surface with substrate-coated coverslips but no enrichment on poly-l-lysine control. Using 3D live-cell two-photon microscopy we determined the spatial distribution of glucose-induced fusion of individual insulin granules. Granule fusion was enriched towards substrates-coated coverslips but on poly-l-lysine control granule fusion occurred all over the cell surface. Using microcontact printing to further pattern basement membrane proteins on the coverslips surface, we manipulated the area where the granules fused on the coverslips surface. To identify the mechanism of beta cell interaction with the substrate we bathed the cells in drugs that affect the formation of focal adhesion such as FAK inhibitor and beta1-integrin blocking antibody. We showed that the targeting secretory response is beta1-integrin dependent.

 In summary, our results provide evidence that basement membrane proteins are functionally important for targeting of insulin secretion and this process might be mediated through beta1-integrin.

  1. LOW, J. T., ZAVORTINK, M., MITCHELL, J. M., GAN, W. J., DO, O. H., SCHWIENING, C. J., GAISANO, H. Y. & THORN, P. 2014. Insulin secretion from beta cells in intact mouse islets is targeted towards the vasculature. Diabetologia, 57, 1655-63.
  2. GAN, W. J., ZAVORTINK, M., LUDICK, C., TEMPLIN, R., WEBB, R., MA, W., PORONNIK, P., PARTON, R. G., GAISANO, H. Y., SHEWAN, A. M. & THORN, P. 2017. Cell polarity defines three distinct domains in pancreatic beta-cells. Journal of Cell Science, 130, 143-151.