Feline Lindhout

112 4 RESULTS ER proteins VAPA and VAPB are involved in regulating SV cycling To determine whether the ER proteins VAPA and VAPB could be involved in modulating presynaptic function, we first mapped their subcellular localization in primary rat hippocampal neurons. Similar as reported previously in Drosophila neurons, we found that endogenous VAPA and VAPB appeared as punctae present along ER structures in axons which often co-localized with presynaptic marker synaptotagmin (Syt; Pennetta et al, 2002).At somatodendritic regions, endogenousVAPAandVAPB revealedamorediffusepatchy staining pattern that co-localized with expressed ER membrane protein Sec61β (Fig 1A).