Tomosyn interacts with the t-SNAREs syntaxin4 and SNAP23 and plays a role in insulin-stimulated GLUT4 translocation.
The Sec1p-like/Munc18 (SM) protein Munc18a binds to the neuronal t-SNARE Syntaxin1A and inhibits SNARE complex assembly. Tomosyn, a cytosolic Syntaxin1A-binding protein, is thought to regulate the interaction between Syntaxin1A and Munc18a, thus acting as a positive regulator of SNARE assembly. In the present study we have investigated the interaction between b-Tomosyn and the adipocyte SNARE complex involving Syntaxin4/SNAP23/VAMP-2 and the SM protein Munc18c, in vitro, and the potential involvement of Tomosyn in regulating the translocation of GLUT4 containing vesicles, in vivo. Tomosyn formed a high affinity ternary complex with Syntaxin4 and SNAP23 that was competitively inhibited by VAMP-2. Using a yeast two-hybrid assay we demonstrate that the VAMP-2-like domain in Tomosyn facilitates the interaction with Syntaxin4. Overexpression of Tomosyn in 3T3-L1 adipocytes inhibited the translocation of green fluorescent protein-GLUT4 to the plasma membrane. The SM protein Munc18c was shown to interact with the Syntaxin4 monomer, Syntaxin4 containing SNARE complexes, and the Syntaxin4/Tomosyn complex. These data suggest that Tomosyn and Munc18c operate at a similar stage of the Syntaxin4 SNARE assembly cycle, which likely primes Syntaxin4 for entry into the ternary SNARE complex.
Pubmed ID: 12832401 RIS Download
3T3 Cells | Animals | Carrier Proteins | Cell Differentiation | Cloning, Molecular | Glucose Transporter Type 4 | Insulin | Kinetics | Membrane Proteins | Mice | Molecular Sequence Data | Monosaccharide Transport Proteins | Munc18 Proteins | Muscle Proteins | Nerve Tissue Proteins | Neurons | Neuropeptides | Protein Binding | Protein Transport | Proteins | Qa-SNARE Proteins | Qb-SNARE Proteins | Qc-SNARE Proteins | R-SNARE Proteins | Recombinant Fusion Proteins | Recombinant Proteins | Vesicular Transport Proteins