NSF-independent fusion mechanisms

Article Abstract:

The SNARE hypothesis suggests that vesicle targeting and fusion are dependent on membrane-specific soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptors. However, two fusion events show that vesicle fusion can occur independent of NSF. The first event involving homotypic endoplasmic reticulum fusion showed that membranes can still carry out fusion mechanisms even in the absence of NSF in the reaction. In the second event, apical vesicle transport in Madin-Darby canine kidney cells was not affected by treatments containing the components essential to the SNARE hypothesis, indicating NSF-independent fusion is possible.

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Calcium mobilization is required for nuclear vesicle fusion in vitro: implications for membrane traffic and IP3 receptor function

Article Abstract:

The fusion of nuclear vesicles bound to chromatin in xenopus egg extracts was examined, and the ratio function of Ca2+ during nuclear envelope organization was studied in vitro. The assumption that fusion needs Ca2+ mobilization through IP3 receptors was tested. 5 mM BAPTA, a Ca2+ buffer that suppresses cytosolic (Ca2+) gradients, impairs fusion. In an IP3-reversible fashion, heparin, a powerful antagonist of IP3 receptors, obstructed fusion autonomously. Nuclear vesicle fusion may be controlled by phosphoinositide signaling.

Analysis, Influence, Observations, Chromatin, Phosphoinositides, Phosphatidylinositols

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A targeting signal in VAMP regulating transport to synaptic vesicles

Article Abstract:

Point mutations on the membrane transport of VAMP in transfected PC12 cells were measured to identify the signals for synaptic vesicle targeting. A signal was detected in celluberin, a protein homologous to VAMP-2 in PC12 cells. This signal requires amphiphatic helices containing a single sorting receptor, which enhances the ability of VAMP to form complexes with the synaptic vesicle. This suggests that this signal may also have a role in v-SNARE function in vesicle transport and membrane fusion.

Membrane proteins

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