Sensing And Signalling Of Extracellular Ca2+ In The Islet Of Langerhans

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This project aims to develop a new sensing platform to resolve a long-standing puzzle: how extracellular Ca2+ coordinates pancreatic islet beta-cells for pulsatile insulin secretion. The latter is key to maintain the blood glucose homeostasis.Free ionic Ca2+ is now recognised as an indispensable messenger in mediating cellular activities in nearly every aspect of cellular life for almost all mammalian cells. Although the roles of intracellular Ca2+ in relation to different biological functions have been well characterised, insights into extracellular Ca2+ are constrained by the lack of appropriate sensing methodology capable of distinguishing the subtle changes of Ca2+ over the high basal level (e.g., micromolar scale variances in millimolar order baseline). For one sensor mainstream - fluorescent indicators, they are particularly limited by the background autofluorescence (due to the use of a shorter wavelength excitation, indicators themselves fluoresce with longer wavelength emissions even in the absence of ions of interest). To overcome this limit, the proposed research will introduce state-of-the-art upconversion luminescence, which features the capacity of converting 980 nm infrared light excitation into visible emissions, to combine with conventional fluorescent indicators. Such a hybrid sensor will represent the world-first one that enables characterising extracellular Ca2+ quantitatively.The upconversion-synergised hybrid sensor will then be applied to address how extracellular Ca2+ participates in coordinating pulsatile insulin secretion from pancreatic islet beta-cells - a key metabolic process coupled to glucose metabolism. The advent of such a sensor, in conjunction with a bespoke microfluidic device, will provide an opportunity to quantify the link between extracellular Ca2+ and pulsatile insulin secretion in isolated islets from mice at different metabolic states (health, prediabetes and type 2 diabetes). These analyses will lead to fundamental knowledge gains which can improve the current understanding on the pathophysiology of type 2 diabetes and may suggest new therapeutic strategies for the management of this major chronic disorder, thereby benefiting people living with type 2 diabetes (in 2021, 4.9 million in the UK and 536.6 million worldwide).