Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Poster Abstracts

34-POS Board 12 PHOSPHATIDIC ACID REGULATES MULTIPLE STEPS ALONG THE JOURNEY OF SECRETORY VESICLES

Nicolas Vitale ; 1 CNRS, INCI, Strsabourg, France

Hormone and neurotransmitter release is tightly controlled by membrane-associated proteins such as SNAREs, but lipids, as major components of membranes have long been suspected to also play important functions. However, until recently little is known about contribution of the lipidic membrane composition in regulated exocytosis due to the lack of modern tools to play with lipids in cells. Using adrenal chromaffin cells as a model, associated with genetic, silencing, and pharmacological approaches, we report here that formation of PA from phosphatidylcholine by the enzyme phospholipase D1 (PLD1) regulates catecholamine release efficiency. Moreover, using a combination of electrochemical measurement of single cell catecholamine secretion and electron microscopy of roof-top membrane sheets, we have shown that diverse PA species, depending on their unsaturation degree, are involved in granule docking and fusion kinetics. Hence, restoration experiments identified that poly-unsaturated (DHA)-containing PA regulates fusion pore stability and expansion, whereas mono-unsaturated PA controls vesicle docking. Then we extended this work to discover that PA not only modulates calcium-regulated exocytosis, but also granular transport to the cell periphery and compensatory endocytosis. Indeed, using spinning disk confocal microscopy, we unraveled that inhibition of PLD activity also reduced the velocity of granules undergoing a directed motion under the plasma membrane. Furthermore, dopamine β -hydroxylase internalization assays revealed that PA production by PLD is required for an optimal recovery of vesicular membrane content by compensatory endocytosis. Thus, PA seems an important modulator of different steps underlying neuroendocrine secretion, supporting findings in other cell models. The development of novel tools to precisely follow the dynamics of PA in membrane, associated with optogenetic control of its metabolism will provide further insight on the key roles of the different species of PA along the journey of secretory vesicles from biogenesis to docking and fusion ending by the recycling of vesicular content by endocytosis.

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