Abstract

SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins are essential constituents of the intracellular trafficking machinery. The variable C-terminus in the two rat VAMP-1 splice isoforms VAMP-1a and -1b potentially acts as a sorting signal since similar changes at the C-terminal end of a human VAMP-1 splice isoform resulted in its sorting to mitochondria. To evaluate differences in the subcellular localization of these two v-SNARE proteins, GFP and RFP tagged VAMP-1a and -1b proteins were expressed in HeLa, COS-7 and MDCK cells and evaluated by conventional confocal as well as total internal reflection fluorescence (TIRF) microscopy. Regions consistent with the endoplasmic reticulum (ER) and Golgi apparatus demonstrated a major overlap of both signals. In the periphery, vesicular structures were observed that expressed mainly one of both isoforms. Within our experimental settings, we could not observe sorting of any of the two isoforms to mitochondria or peroxisomes, whereas both isoforms were found expressed in a minor subset of singular vesicles, which sporadically appear to colocalize with the exocyst marker EXOC3/Sec6. Since vesicular structures were seen that expressed only one of the two splice variants, it is possible that VAMP-1a and VAMP-1b are sorted to distinct cellular compartments which require further characterization.

View details for DOI 10.1139/bcb-2016-0184

View details for PubMedID 28314111