Characterization of phogrin-GCaMP6m-XC, a label to measure perigranular Ca2+-concentrations

Background and aims The beta cell and the other endocrine cells of the pancreatic islet release their respective hormones by triggered exocytosis. The final fusion step results from the influx of Ca2+ via voltage-dependent Ca2+-channels. However, metabolic stimuli like glucose release more insulin than purely depolarizing stimuli even though the Ca2+ increase is often less marked. To get a clearer view on the exocytosis-relevant Ca2+-concentration a site-specific label is needed.