Membrane-Targeted palGFP Predominantly Localizes to the Plasma Membrane but not to Neurosecretory Vesicle Membranes in Rat Oxytocin Neurons

Abstract

Recent advances in viral vector technology, specifically using adeno-associated virus (AAV) vectors, have significantly expanded possibilities in neuronal tracing. We have utilized the Cre/loxP system in combination with AAV techniques in rats to explore the subcellular localization of palmitoylation signal-tagged GFP (palGFP) in oxytocin-producing neurosecretory neurons. A distinctive branching pattern of single axons was observed at the level of the terminals in the posterior pituitary. Despite challenges in detecting palGFP signals by fluorescent microscopy, immunoelectron microscopy demonstrated predominant localization on the plasma membrane, with a minor presence on the neurosecretory vesicle membrane. These findings suggest that membrane-anchored palGFP may undergo exocytosis, translocating from the plasma membrane to the neurosecretory vesicle membrane. In this study, we observed characteristic axon terminal structures in the posterior pituitary of oxytocin neurons. This study indicates the importance of understanding the plasma membrane-specific sorting system in neuronal membrane migration and encourages future studies on the underlying mechanisms.