Ahmed Shaaban

Postdoc, Imig Lab

Title: Dissecting functional vesicle pools and serotonin release kinetics from mouse enterochromaffin cells

Abstract: Enteroendocrine cells (EECs) are a group of cells specialized in sensing a wide range of stimuli such as bacterial metabolites, toxins, and mechanical stimulation, and in transducing these stimuli into signals to the brain via the release of peptide hormones and neurotransmitters. A subtype of EECs referred to as Enterochromaffin (EC) cells produce and release more than 90% of the body’s serotonin (5-HT), which is an important regulator of various physiological processes including gut motility. EC cell dysfunction has been associated with several disease states such as irritable bowel syndrome, inflammation, nausea, and visceral hypersensitivity.  To gain a better understanding of the molecular mechanisms that mediate EC cell function and 5-HT release, we have established an in vitro experimental workflow using epithelial 2D‑monolayer cultures from a transgenic mouse line that specifically expresses cyan fluorescent protein (CFP) under the control of the  Tryptophan hydroxylase 1 (Tph1) promoter, allowing us to identify EC cells in culture for high-resolution functional assays. Measuring changes in membrane capacitance in response to a series of depolarization pulses, and single-cell carbon fiber amperometry, we were able to characterize functional vesicle pools in isolated EC cells from different gut regions and characterize the kinetics of the 5-HT release from individually fusing vesicles. We anticipate that this methodological approach will ultimately make it possible to study EC cell function and 5-HT release from human EC cells in various different disease contexts.