Inhibition of the binding of SNAP-23 to syntaxin 4 by Munc18c.
SNARE proteins have been implicated in the insulin-induced translocation of vesicles containing the GLUT4 glucose transporter to the plasma membrane of adipocytes. The role of the target SNARE SNAP-25 or its homologs in this process was investigated by screening a mouse adipocyte cDNA library with rat SNAP-25 and human SNAP-23 cDNA probes. Both positive clones isolated encoded a protein with 87% sequence identity to human SNAP-23, and which was therefore designated mouse SNAP-23. Immunoblot and immunofluorescence analyses revealed that SNAP-23 is located predominantly in the plasma membrane of 3T3-L1 adipocytes incubated in the absence or presence of insulin. Of syntaxins 1 to 5, SNAP-23 bound with the highest affinity to syntaxins 1 and 4 in the yeast two-hybrid system. Expression of SNAP-23, syntaxin 4, and the syntaxin-binding protein Munc 18c in COS cells revealed that Munc18c reduced the amount of SNAP-23 bound to syntaxin 4 in a concentration-dependent manner. These results suggest that the binding of SNAP-23 to syntaxin 4 is inhibited by Munc18c in adipocytes.
Araki
S
S
Second Department of Internal Medicine, Kobe University School of Medicine, Japan.
Tamori
Y
Y
Kawanishi
M
M
Shinoda
H
H
Masugi
J
J
Mori
H
H
Niki
T
T
Okazawa
H
H
Kubota
T
T
Kasuga
M
M
D017667:Adipocytes / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D051938:Munc18 Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins / Q000502:physiology*; D011485:Protein Binding; D011487:Protein Conformation; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017421:Sequence Analysis; D014162:Transfection; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D051938:Munc18 Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D011994:Recombinant Proteins; C495692:SLC2A4 protein, human; C100493:SNAP23 protein, human; C495693:Slc2a4 protein, mouse; C495694:Slc2a4 protein, rat; C107017:Snap23 protein, mouse; C497943:Stxbp3 protein, mouse; C497944:Stxbp3 protein, rat; D033921:Vesicular Transport Proteins