A conserved mechanism of synaptogyrin localization

We have studied the localization of synaptogyrin family members in vivo. Bo th native and green fluorescent protein (GFP)-tagged Caenorhabditis elegans synaptogyrin (SNG-1) are expressed in neurons and synaptically localized. Deletion and mutational analysis with the use of GFP-tagged SNG-1 has defin ed a 38 amino acid sequence within the C terminus of SNG-1 and a single arg inine in the cytoplasmic loop between transmembrane domain 2 and 3 that are required for SNG-1 localization. These domains may represent components of signals that target synaptogyrin for endocytosis from the plasma membrane and direct synaptogyrin to synaptic vesicles, respectively. In chimeric stu dies, these regions were sufficient to relocalize cellugyrin, a nonneuronal form of synaptogyrin, from nonsynaptic regions such as the sensory dendrit es and the cell body to synaptic vesicles. Furthermore, GFP-tagged rat syna ptogyrin is synaptically localized in neurons of C. elegans and in cultured hippocampal neurons. Similarly, the C-terminal domain of rat synaptogyrin is necessary for localization in hippocampal neurons. Our study suggests th at the mechanisms for synaptogyrin localization are likely to be conserved from C. elegans to vertebrates.