Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Poster Abstracts

19-POS Board 7 PACAP ACTIVATION OF PHOSPHOLIPASE C EPSILON MOBILIZES CALCIUM AND STIMULATES SECRETION IN CHROMAFFIN CELLS

Xiaohuan Chen 1 ; Alan V Smrcka 2 ; Daniel Axelrod 3 ; David I Yule 4 ; Arun Anantharam 1 ; 1 The University of Toledo, Neurosciences, Toledo, OH, USA 2 University of Michigan, Pharmacology, Ann Arbor, MI, USA 3 University of Michigan, Physics and LSA Biophysics, Ann Arbor, MI, USA 4 University of Rochester, Pharmacology and Physiology, Rochester, NY, USA

The sympathoadrenal system coordinates stress responses through the regulation of catecholamine secretion from chromaffin cells, which convert neurotransmitter signals into effector outputs, consequently modulating organ function. Pituitary adenylate cyclase-activating polypeptide (PACAP) serves as a critical modulator of this secretion, although its signaling mechanisms have not been fully understood. Our study, employing pharmacological, optical, and electrophysiological methodologies, provides new insights on PACAP-stimulated secretion. We found that PACAP activates multifocal calcium signaling via phospholipase C epsilon (PLCε), thereby driving exocytosis. PACAP elevates cytosolic calcium (Ca 2+ ) levels through a dual mechanism involving Ca 2+ influx via L- type channels and PLCε -dependent inositol 1,4,5 trisphosphate receptor (IP 3 R)-mediated endoplasmic reticulum (ER) Ca 2+ release. We further observed that PLCε knockout, IP 3 R inhibition, or ER Ca 2+ depletion effectively hinder PACAP evoked Ca 2+ signals and secretion. Notably, in cells lacking PLCε, only the Ca 2+ signals and secretory responses specific to PACAP (not those induced by dimethylphenylpiperazinium, a nicotinic acetylcholine receptor agonist) were abolished. Additionally, our results showed that PLCε knockout can inhibit PACAP -induced production of the second messenger diacylglycerol, which, in turn, activates protein kinase C (PKC), suggesting a role for PKC in PACAP-induced secretion. In conclusion, our study identifies PLCε as a key signaling intermediary that links PACAP to chromaffin cell multifocal Ca 2+ signals, facilitating exocytosis. These results suggest novel ways in which splanchnic signaling is decoded into neuroendocrine responses that orchestrate stress reactions.

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