Figure 9.

Model depicting the role of septin filaments in lytic granule release. Based on the data shown here, we propose that while the septin cytoskeleton is depleted from the CS, it is maintained at the edges of the synapse but is also associated with lytic granules. As a result, septin filaments are brought back to the CS along with the lytic granules, where they participate in stabilizing the STX11:STBP2 interaction to promote lytic granule fusion and release of cytotoxic components. In the absence of septin 7, there is defective lytic granule release due in part to the impaired interaction of STX11 with STXBP2.