Shao K, Li F, Yang Y, Wang N, Gao XD, Nakanishi H

Syntaxin-1A and Sso1 are syntaxin family SNARE proteins engaged in synaptic vesicle fusion and yeast exocytosis. The syntaxin-1A SNARE motif can form a fusogenic SNARE complex with Sso1 partners. However, a chimera in which the SNARE motif in syntaxin-1A is introduced into Sso1 was not functional in yeast because the ...

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chimera is retained in the ER. Through the analysis of the transport defect of Sso1/syntaxin-1A chimeric SNAREs, we found that their SNARE motifs have distinctive properties.Sso1, syntaxin-1A, and Sso1/syntaxin-1A chimeric SNAREs were expressed in yeast cells and their localization and interaction with other SNAREs are analyzed.SNARE proteins containing the syntaxin-1A SNARE motif exhibit a transport defect because they form a cis-SNARE complex in the ER. Ectopic SNARE complex formation can be prevented in syntaxin-1A by binding to a Sec1/Munc-18-like (SM) protein. In contrast, the SNARE motif of Sso1 does not form an ectopic SNARE complex. Additionally, we found that the SNARE motif in syntaxin-1A, but not that in Sso1, self-interacts, even when it is in the inactive form and bound to the SM protein.The SNARE motif in syntaxin-1A, but not in Sso1, likely forms ectopic SNARE complex. Because of this property, the SM protein is necessary for syntaxin-1A to prevent its promiscuous assembly and to promote its export from the ER.Properties of SNARE motifs affect characteristics of SNARE proteins. The regulatory mechanisms of SNARE proteins are, in part, designed to handle such properties.

Date: Oct. 01, 2020

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