SKM 2021 – wissenschaftliches Programm
CPP 6.12: Poster
Dienstag, 28. September 2021, 17:30–19:30, P
Stability of the hemifusion diaphragm and the rim pore — •Yuliya Smirnova and Marcus Müller — Institute for Theoretical Physics, Georg-August University, Göttingen, Germany
Synapic transmission is a fundamental biophysical process that involves the exocytosis (neurotransmitter release) and endocytosis (vesicle recovery) of small synaptic vesicles at the presynaptic plasma membrane. Whereas the molecular mechanisms of these topology-altering membrane processes are only incompletely understood, it is hypothesized that a hemifusion diaphragm (HD), i.e., an extended single-membrane-thick, lipidic connection between the two apposing membranes, is an important intermediate state. We develop a phenomenological model to investigate the free-energy landscape of a HD with a (rim) pore (RP) that is formed inside the HD and borders the three-bilayer junction at the HD's rim. In the limit that the RP attains the size of the HD, a complete fusion pore is formed. In the absence of the RP, HDs of different sizes are (meta)stable in the canonical ensemble. It appears, however, to be difficult to stabilize a HD+RP complex in the canonical ensemble. Membrane tension, intermembrane distance, and the line tensions of a membrane pore, a HD, and a fusion pore, as well as external control of the HD's size are important parameters that dictate the (meta)stability of the HD+RP complex and, thereby, the pathway of synaptic transmission.