Munc13-1 is a large banana-shaped soluble protein that involved in the regulation of synaptic vesicle docking and fusion. Recent studies suggest multiple copies form nano-assemblies active zones neurons. However, it not known whether such clustering correlated with multivalent binding to vesicles or specific plasma membrane domains at sites zone. The functional significance putative also unknow...

After internalization from the plasma membrane, activated EGF receptors (EGFRs) are delivered to multivesicular bodies (MVBs). Within MVBs, EGFRs are removed from the perimeter membrane to internal vesicles, thereby being sorted from transferrin receptors, which recycle back to the plasma membrane. The phosphatidylinositol (PI) 3'-kinase inhibitor, wortmannin, inhibits internal vesicle formatio...

The shedding of membrane vesicles from the cell surface is a vital process considered to be involved in cell-cell and cell-matrix interactions and in tumor progression. By immunoelectron microscopic analysis of surface replicas of 8701-BC human breast carcinoma cells, we observed that membrane vesicles shed from plasma membranes contained densely clustered gelatinase B [matrix metalloproteinase...

CAPS-1 is required for Ca2+-triggered fusion of dense-core vesicles with the plasma membrane, but its site of action and mechanism are unknown. We analyzed the kinetics of Ca2+-triggered exocytosis reconstituted in permeable PC12 cells. CAPS-1 increased the initial rate of Ca2+-triggered vesicle exocytosis by acting at a rate-limiting, Ca2+-dependent prefusion step. CAPS-1 activity depended upo...

Fertilization typically involves membrane fusion between sperm and eggs. In Drosophila, however, sperm enter eggs with membranes intact. Consequently, sperm plasma membrane breakdown (PMBD) and subsequent events of sperm activation occur in the egg cytoplasm. We previously proposed that mutations in the sneaky (snky) gene result in male sterility due to failure in PMBD. Here we support this pro...

Secretion occurs in all cells of multicellular organisms and involves the delivery of secretory products packaged in membrane-bound vesicles to the cell exterior. Specialized cells for neurotransmission, enzyme secretion or hormone release utilize a highly regulated secretory process. Secretory vesicles are transported to specific sites at the plasma membrane, where they dock and fuse to releas...

Cellular communication depends on membrane fusion mechanisms. SNARE proteins play a fundamental role in all intracellular fusion reactions associated with the life cycle of secretory vesicles, such as vesicle–vesicle and vesicle plasma membrane fusion at the porosome base in the cell plasma membrane. We present growth and elimination (G&E), a birth and death model for the investigation of granu...

Neurotransmission requires a continuously available pool of synaptic vesicles (SVs) that can fuse with the plasma membrane and release their neurotransmitter contents upon stimulation. After fusion, SV membranes and membrane proteins are retrieved from the presynaptic plasma membrane by clathrin-mediated endocytosis. After the internalization of a clathrin-coated vesicle, the vesicle must uncoa...

Syntaxins are membrane integrated Q-SNARE proteins known to participate in exocytosis. Vesicle docking involves the binding of two plasma membrane proteins, syntaxin and SNAP-25, to the vesicle membrane protein VAMP to form a stable trimeric core complex; synaptophysin is thought to regulate the formation of this complex. Although the members of Q-SNARE proteins are characterized in somatic cel...

Synaptic vesicles are synthesized at a rapid rate in nerve terminals to compensate for their rapid loss during neurotransmitter release. Their biogenesis involves endocytosis of synaptic vesicle membrane proteins from the plasma membrane and requires two steps, the segregation of synaptic vesicle membrane proteins from other cellular proteins, and the packaging of those unique proteins into ves...