Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Poster Abstracts

15-POS Board 5 INSULIN BIPHASIC RELEASE: UNDERSTANDING THE MOLECULAR MECHANISMS AND DETERMINANTS OF FIRST AND SECOND PHASES

Sathish Ramakrishnan 1 ; 1 Yale University, Pathology & Nanobiology, New Haven, CT, USA

The pancreatic β -cells store insulin hormone and C-peptide in large dense-core vesicles (LDCV), which are released in response to external stimuli to maintain glucose homeostasis. Diabetes occurs when there is a failure or loss of insulin- secreting β -cells. The biphasic release of insulin is mediated by SNARE proteins and their isoforms, but the specific mechanisms are unclear. Our understanding of how SNARE proteins regulate biphasic release modes, pore, and fusion kinetics remains unclear. Distinct SNARE complexes and regulatory proteins are thought to control the first and second phases of insulin release. However, the need for a second SNARE isoform complex and its role in modulating the two phases of exocytosis is unclear. Using suspended lipid membrane platforms, single vesicle cellular assays, and nanoluc secretion assays, to investigate the first and second phases of insulin release and found that distinct SNARE complexes and synaptotagmin isoforms play a major role in determining the type of vesicle release in each phase. We also found that the number of SNARE complexes between the vesicle and plasma membrane strongly determines LDCV kinetics. The study presents a deeper insight into LCDV fusion and a novel model for insulin LDCV exocytosis that will benefit the membrane fusion community.

98