Role for the Acto-myosin complex in the dynamics of regulated exocytosis revealed by intravital microscopy in live rodents

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NIDCR	CELLBIO-14

Authors

• A Masedunskas
• M Sramkova
• L Parente
• K Uzzun Sales
• P Amornphimoltham
• R Weigert

Abstract

Regulated exocytosis is a fundamental process in all secretory organs, and unraveling its complex molecular machinery is key in understanding both their physiology and dysfunctions. Although the stimulated secretion has been extensively studied in live animals, all the information available on the dynamics and the regulation of secretory vesicles has been derived from cultured cell or organ cultures. Here we show for the first time that the dynamics of secretory events can be dissected and studied in live animals by using intravital microscopy under physiological conditions. We used the salivary glands of live rodents as a model for exocrine secretion, showing that in acinar cells large secretory granules fuse with the apical plasma membrane where they completely collapse without any evidence of compound exocytosis, as previously reported in ex-vivo models. We also show that upon fusion of the lipid bi-layers and the diffusion of the membranes from the apical membrane, actin and nonmuscle myosin II assemble around the granules. This scaffold facilitates the completion of fusion through the motor activity of myosin II and prevents the homotypic fusion between the granules. Our results show that intravital microscopy provides a unique opportunity to address many cell biological questions in physiological conditions.

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