Vesl-1S/Homer 1a, reported originally as Vesl/ Homer, was isolated as a synaptic plasticity-regulated gene. The expression of Vesl-1S/Homer 1a is regulated during long-term potentiation in the hippocampus, Vesl-1L/Homer 1c, which appears to be formed by a splicing event, shares the N-terminus with Vesl-1S/ Homer la and also contains additional amino acids at the C-terminus. The short form and the long form of the family members both interact with group 1 metabotropic glutamate receptors (mGluRs). We herein report the identification of syntaxin 13 as a molecule that interacts with Vesl-1L using yeast two-hybrid screening. Syntaxin 13 is a member of the syntaxin family and is regarded as soluble N-ethylmaleimide-sensitive attachment proteins receptors (SNAREs) in the endosomal membranes. The interaction of Vesl-1L and syntaxin 13 was biochemically confirmed by in vitro binding assays. The coexpression of the two proteins in the transfected cells resulted in a colocalization in the intracellular vesicle-like structures. We thus propose that the association of Vesl-1L with syntaxin 13 plays a role in the translocation of Vesl-1L to the intracellular organelles.