Abstract
In neurosecretory cells, secretory vesicles (SVs) undergo Ca(2+)-dependent fusion with the plasma membrane to release neurotransmitters. How SVs cross the dense mesh of the cortical actin network to reach the plasma membrane remains unclear. Here we reveal that, in bovine chromaffin cells, SVs embedded in the cortical actin network undergo a highly synchronized transition towards the plasma membrane and Munc18-1-dependent docking in response to secretagogues. This movement coincides with a translocation of the cortical actin network in the same direction. Both effects are abolished by the knockdown or the pharmacological inhibition of myosin II, suggesting changes in actomyosin-generated forces across the cell cortex. Indeed, we report a reduction in cortical actin network tension elicited on secretagogue stimulation that is sensitive to myosin II inhibition. We reveal that the cortical actin network acts as a 'casting net' that undergoes activity-dependent relaxation, thereby driving tethered SVs towards the plasma membrane where they undergo Munc18-1-dependent docking.
Highlights
In neurosecretory cells, secretory vesicles (SVs) undergo Ca2 þ -dependent fusion with the plasma membrane to release neurotransmitters
To exclude the possibility of an artifactual increase in fluorescence intensity associated with an overall movement of the cell towards the coverslip, we expressed the plasma membrane marker green fluorescent protein (GFP)–glycosyl phosphatidyl inositol (GPI) and found no significant change in fluorescence in the GFP–GPI channel (Supplementary Fig. 1d), confirming that secretagogue stimulation promotes translocation of F-actin and vesicles without causing any significant displacement of the GFP– GPI-labelled plasma membrane
We discovered that myosin II maintains the cortical actin network in tension at rest and that secretagogue stimulation elicits a relaxation that drives the cortical actin network and tethered SVs towards the plasma membrane
Summary
Secretory vesicles (SVs) undergo Ca2 þ -dependent fusion with the plasma membrane to release neurotransmitters. In bovine chromaffin cells, SVs embedded in the cortical actin network undergo a highly synchronized transition towards the plasma membrane and Munc18-1-dependent docking in response to secretagogues. Recent work has highlighted a role for myosin II in exocytosis[12,13,14,15,16,17], as well as demonstrating its ability to maintain the cortical actin network under tension[18,19,20] How these molecular motors act to direct SVs towards their docking sites remains unclear. We reveal that secretagogue stimulation promotes a reduction in cortical actin network tension, facilitating the movement of SVs towards the plasma membrane where they undergo Munc18-1-dependent docking
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.
