Evidence that electrostatic interactions between vesicle-associated membrane protein 2 and acidic phospholipids may modulate the fusion of transport vesicles with the plasma membrane.
The juxtamembrane domain of vesicle-associated membrane protein (VAMP) 2 (also known as synaptobrevin2) contains a conserved cluster of basic/hydrophobic residues that may play an important role in membrane fusion. Our measurements on peptides corresponding to this domain determine the electrostatic and hydrophobic energies by which this domain of VAMP2 could bind to the adjacent lipid bilayer in an insulin granule or other transport vesicle. Mutation of residues within the juxtamembrane domain that reduce the VAMP2 net positive charge, and thus its interaction with membranes, inhibits secretion of insulin granules in beta cells. Increasing salt concentration in permeabilized cells, which reduces electrostatic interactions, also results in an inhibition of insulin secretion. Similarly, amphipathic weak bases (e.g., sphingosine) that reverse the negative electrostatic surface potential of a bilayer reverse membrane binding of the positively charged juxtamembrane domain of a reconstituted VAMP2 protein and inhibit membrane fusion. We propose a model in which the positively charged VAMP and syntaxin juxtamembrane regions facilitate fusion by bridging the negatively charged vesicle and plasma membrane leaflets.
Williams
Dumaine
D
Department of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Vicôgne
Jérome
J
Zaitseva
Irina
I
McLaughlin
Stuart
S
Pessin
Jeffrey E
JE
D041721:3T3-L1 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism; D016415:Sequence Alignment; D055672:Static Electricity; D022161:Transport Vesicles / Q000378:metabolism*; D050988:Vesicle-Associated Membrane Protein 2 / Q000235:genetics / Q000378:metabolism*
D051275:Glucose Transporter Type 4; D007328:Insulin; D010743:Phospholipids; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; C495693:Slc2a4 protein, mouse; D050988:Vesicle-Associated Membrane Protein 2