Abstract

MOLECULAR MACHINERY FOR THE ‘KISS AND RUN’ MECHANISM OF INSULIN SECRETION by AKSHATA RAMESH NAIK August 2019 Advisor: Bhanu P. Jena, Ph.D. Major: Physiology Degree: Doctor of Philosophy The insulin secreting porosome is a supramolecular lipo-protein complex that measures roughly 100 – 120 nm in diameter. Porosomes allow transient fusion of insulin secretory granules to the cell plasma membrane and mediates partial release of secretory contents. Post secretion, the secretory granule reseals and re-enters to the cell interior. This is in contrast to the ‘total fusion’ phenomenon, where secretory vesicles completely fuse at the cell plasma membrane and release all of the contents to the cell exterior. This study involved a deeper understanding of the transient or ‘kiss-and-run’ mechanism of cell secretion that involves the insulin secreting porosome complex. In addition to the porosome, two other components of transient cell secretion, namely the t/v SNARE complex and the insulin secreting granules (ISGs) were also studied. We demonstrated for the very first time in the history of porosomes, its functional and stable reconstitution into live insulin secreting mouse insulinoma cells leading to improved glucose stimulated insulin releasing from the reconstituted cells. Further, we demonstrated a drop in intracellular pH once a cell has been stimulated for secretion. This lowering of pH is critical for locking in place, the t/v SNARE complex that are present at the base of the porosome.