Hauke S, Dutta AK, Eisenbeis VB, Bezold D, Bittner T, Wittwer C, Thakor D, Pavlovic I, Schultz C, Jessen HJ. Photolysis of cell-permeant caged inositol pyrophosphates controls oscillations of cytosolic calcium in a β-cell line.
Chem Sci 2019;
10:2687-2692. [PMID:
30996985 PMCID:
PMC6419925 DOI:
10.1039/c8sc03479f]
[Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Accepted: 01/09/2019] [Indexed: 12/16/2022] Open
Abstract
β-Cells respond directly to the intracellular photochemical release of caged inositol pyrophosphate isomers with modulations of oscillations in cytosolic Ca2+.
Among many cellular functions, inositol pyrophosphates (PP-InsPs) are metabolic messengers involved in the regulation of glucose uptake, insulin sensitivity, and weight gain. However, their mechanisms of action are still poorly understood. So far, the influence of PP-InsPs on cellular metabolism has been studied by overexpression or knockout/inhibition of relevant metabolizing kinases (IP6Ks, PPIP5Ks). These approaches are, inter alia, limited by time-resolution and potential compensation mechanisms. Here, we describe the synthesis of cell-permeant caged PP-InsPs as tools to rapidly modulate intracellular levels of defined isomers of PP-InsPs in a genetically non-perturbed cellular environment. We show that caged prometabolites readily enter live cells where they are enzymatically converted into still inactive, metabolically stable, photocaged PP-InsPs. Upon light-triggered release of 5-PP-InsP5, the major cellular inositol pyrophosphate, oscillations of intracellular Ca2+ levels in MIN6 cells were transiently reduced to spontaneously recover again. In contrast, uncaging of 1-PP-InsP5, a minor cellular isomer, was without effect. These results provide evidence that PP-InsPs play an active role in regulating [Ca2+]i oscillations, a key element in triggering exocytosis and secretion in β-cells.
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