Abstract
Lipid molecules such as arachidonic acid (AA) and sphingolipid metabolites have been implicated in modulation of neuronal and endocrine secretion. Here we compare the effects of these lipids on secretion from cultured bovine chromaffin cells. First, we demonstrate that exogenous sphingosine and AA interact with the secretory apparatus as confirmed by FRET experiments. Examination of plasma membrane SNARE microdomains and chromaffin granule dynamics using total internal reflection fluorescent microscopy (TIRFM) suggests that sphingosine production promotes granule tethering while arachidonic acid promotes full docking. Our analysis of single granule release kinetics by amperometry demonstrated that both sphingomyelinase and AA treatments enhanced drastically the amount of catecholamines released per individual event by either altering the onset phase of or by prolonging the off phase of single granule catecholamine release kinetics. Together these results demonstrate that the kinetics and extent of the exocytotic fusion pore formation can be modulated by specific signalling lipids through related functional mechanisms.
Highlights
The exocytic fusion of specialized vesicles releasing their content of neurotransmitters and hormones is the central event underlying the physiological function of neuronal and endocrine systems
In order to elucidate the mechanism utilized by signalling lipids to enhance the secretory response [11,12,13], we first tested the possible interaction of exogenous sphingosine and arachidonic acid (AA) with the secretory machinery formed by SNAP-25-syntaxin microdomains in the plasma membrane of chromaffin [16] by using FRET sensitized emission experiments
These experiments were performed by incubation of cultured bovine chromaffin cells expressing SNAP-25-Ds-Red (FRET acceptor) with sphingosine or AA tagged with BODIPY (AA-BODIPY) as donor molecules
Summary
The exocytic fusion of specialized vesicles releasing their content of neurotransmitters and hormones is the central event underlying the physiological function of neuronal and endocrine systems. The SNARE proteins may provide the specificity required for vesicle docking and probably the basic machinery for membrane fusion [4], but it is evident that lipids could be essential players or regulators of exocytosis [5,6,7]. In this respect, because membranes have to adopt different curvatures during fusion, it has been shown that cone-shaped lipids may favor the appropriate membrane geometry and can influence the membrane propensity to fuse [8]. Soluble lipids can affect different SNARE proteins to increase the number of ternary complexes and thereby enhance the secretory properties of neuroendocrine cells [11,12,13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
