The sec6/8 Complex Is Located at Neurite Outgrowth and Axonal Synapse-Assembly Domains

Abstract

The molecules that specify domains on the neuronal plasma membrane for the delivery and accumulation of vesicles during neurite outgrowth and synapse formation are unknown. We investigated the role of the sec6/8 complex, a set of proteins that specifies vesicle targeting sites in yeast and epithelial cells, in neuronal membrane trafficking. This complex was found in layers of developing rat brain undergoing synaptogenesis. In cultured hippocampal neurons, the sec6/8 complex was present in regions of ongoing membrane addition: the tips of growing neurites, filopodia, and growth cones. In young axons, the sec6/8 complex was also confined to periodic domains of the plasma membrane. The distribution of synaptotagmin, synapsin1, sec6, and FM1-43 labeling in cultured neurons suggested that the plasma membrane localization of the sec6/8 complex preceded the arrival of synaptic markers and was downregulated in mature synapses. We propose that the sec6/8 complex specifies sites for targeting vesicles at domains of neurite outgrowth and potential active zones during synaptogenesis.

The Brain Exocyst Complex Interacts with RalA in a GTP-dependent Manner

“…Our finding that the exocyst is another effector for RalA localizes this complex to the mature nerve terminal. The complex was previously localized to growth cones of axons and dendrites in developing neurons, in discrete domains along the axon, and in most newly formed nerve terminals (36). The likely role for the mammalian exocyst in the development of nerve terminal exocytosis and the established role for RalA in endocytosis places RalA in a unique situation where it potentially regulates both, although not necessarily during the same stage of development.…”

Membrane Organization and Dynamics in Cell Polarity

“…In mammalian cells, although the exocyst mostly localizes to internal membrane compartments such as Golgi and recycling endosomes Ang et al 2003;Fölsch et al 2003;Oztan et al 2007), it is recruited to designated regions of the plasma membrane where active exocytosis and membrane expansion occur. For example, in neurons undergoing differentiation or synapse formation, the exocyst is enriched at the expanding neurites and discrete puncta along axons where synapses are forming (Hsu et al 1996;Kee et al 1997;Hazuka et al 1999;Vega and Hsu, 2001;Brown et al 2001;Murthy et al 2003). In migrating cells, the exocyst is recruited to the plasma membrane at the leading edge (Zuo et al 2006;Rosse et al 2006).…”

Phosphatidylinositol 4,5-Bisphosphate Mediates the Targeting of the Exocyst to the Plasma Membrane for Exocytosis in Mammalian Cells

“…However, they are recruited to the PM during a number of cellular processes. For example, in epithelial cells, the exocyst is recruited to the adherens junction region upon cell-cell contact, where it mediates protein and membrane addition at the basolateral domain (Grindstaff et al, 1998;Yeaman et al, 2001); in developing neurons, the exocyst is localized to the growing neurites, where it mediates membrane expansion (Hazuka et al, 1999;Vega and Hsu, 2001); during cell migration, the exocyst is recruited to the leading edges of the PM (Rosse et al, 2006;Zuo et al, 2006).…”