Transient pores in Hemifusion Diaphragms

Material exchange across double membranes, as seen in neurotransmitter release during synaptic exocytosis, involves the formation and poration of a hemifusion diaphragm (HD). The nontrivial geometry of the HD leads to environment-dependent control, regarding the stability and dynamics of the pores required for this kind of exocytosis. We integrate particle simulations, field-theoretic calculations, and phenomenological modelling to investigate mechanisms for controlling pore formation and stability within HDs. Our results show a preference for pores to form at the HD rim, with their stability being influenced by factors such as three line tensions, membrane tension, HD size, and the tendency for lipids to "flip-flop" between bilayer leaflets. Additionally, we explore how these factors could be used by cells or vesicles to regulate pore opening and closing, enabling efficient material transport.