Journal article
Characterization of Munc-18c and Syntaxin-4 in 3T3-L1 Adipocytes: putative role in insulin-dependent movement of glut-4
Journal of Biological Chemistry, Vol.272(10), pp.6179-6186
1997
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Abstract
We have previously identified three mammalian Sec1/Munc-18 homologues in adipocytes (Tellam, J. T., McIntosh, S., and James, D. E. (1995) J. Biol. Chem. 270, 5857-5863). These proteins are thought to modulate the interaction between vesicle membrane and target membrane soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and thus regulate intracellular vesicular transport. This study aimed to further characterize these Munc-18 isoforms and to define their potential role in the trafficking of GLUT-4 in adipocytes, a process reported to involve the vesicle membrane SNARE, VAMP-2. Using an in vitro binding assay with recombinant fusion proteins, we show that Munc-18a and Munc-18b bind to syntaxin-1A, −2, and −3, while Munc-18c binds only to syntaxin-2 and −4. The specific interaction between Munc-18c and syntaxin-4 is of interest because aside from syntaxin-1A, which is not expressed in adipocytes, syntaxin-4 is the only syntaxin that binds to VAMP-2. Using a three-way binding assay, it was shown that Munc-18c inhibits the binding of syntaxin-4 to VAMP-2. The subcellular distribution of syntaxin-4 and Munc-18c was almost identical, both being enriched in the plasma membrane, and both exhibiting an insulin-dependent movement out of an intracellular membrane fraction similar to that observed for GLUT-4. Munc-18b had a similar distribution to Munc-18c and so may also be involved in vesicle transport to the cell surface, whereas Munc-18a was undetectable by immunoblotting in adipocytes. Microinjection of a syntaxin-4 antibody into 3T3-L1 adipocytes blocked the insulin-dependent recruitment of GLUT-4 to the cell surface. These data suggest that syntaxin-4/Munc-18c/VAMP-2 may play a role in the docking/fusion of intracellular GLUT-4-containing vesicles with the cell surface in adipocytes.
Details
- Title
- Characterization of Munc-18c and Syntaxin-4 in 3T3-L1 Adipocytes: putative role in insulin-dependent movement of glut-4
- Creators
- Judy T Tellam - University of QueenslandS Lance Macaulay - CSIROShane Reid McIntosh - University of QueenslandDean R Hewish - CSIROColin W Ward - University of QueenslandDavid E James - University of Queensland
- Publication Details
- Journal of Biological Chemistry, Vol.272(10), pp.6179-6186
- Publisher
- American Society for Biochemistry and Molecular Biology, Inc.
- Identifiers
- 991013019534402368
- Copyright
- This is an Open Access article under the CC BY license.
- Academic Unit
- Faculty of Science and Engineering
- Language
- English
- Resource Type
- Journal article