Munc 18a binding to syntaxin 1A and 1B isoforms defines its localization at the plasma membrane and blocks SNARE assembly in a three-hybrid system assay.
Syntaxin 1 and synaptobrevin/ VAMP play an essential role in synaptic vesicle exocytosis. Two isoforms for each of these proteins, syntaxins 1A and 1B and synaptobrevin/VAMPs 1 and 2, have been found in nerve endings. Morphological and biochemical studies have revealed a characteristic colocalization and selective interactions patterns of syntaxin 1 and synaptobrevin/ VAMP isoforms in nervous and endocrine systems. Moreover, studies in vitro with recombinant proteins have shown characteristic interaction patterns for each syntaxin 1-synaptobrevin/ VAMP pair. The cytosolic protein Munc-18a modulates neurotransmission by inhibiting the binding of synaptobrevin/ VAMP and SNAP-25 to syntaxin 1A. In the present study, several binding assays were used to demonstrate that Munc-18a significantly binds both isoforms of syntaxin 1 (syntaxins 1A and 1B). Moreover, the coexpression of Munc-18a and syntaxin 1A or syntaxin 1B in 29.3 T cells revealed syntaxin 1-dependent localization of Munc-18a in the plasma membrane. By using the three-hybrid system, we showed the inhibitory role of Munc-18a in the formation of syntaxin 1-synaptobrevin/ VAMP complexes regardless of the isoforms. Since Munc-18a can bind both isoforms of syntaxin 1, the present data suggest that this protein is a general modulator of the formation of different SNARE complexes in the nerve endings.[1]References
- Munc 18a binding to syntaxin 1A and 1B isoforms defines its localization at the plasma membrane and blocks SNARE assembly in a three-hybrid system assay. Pérez-Brangulí, F., Muhaisen, A., Blasi, J. Mol. Cell. Neurosci. (2002) [Pubmed]
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