HSV1 vectors to study protein targeting in neurones: are glycosyl-phosphatidylinositol anchors polarized targeting signals in neurones?

In order to characterize protein targeting signals in polarized postmitotic cortical neurones in vitro, we have developed recombinant and amplicon type vectors derived from herpes simplex virus 1 (HSV1) to transfer genes into these cells. We examined the targeting of both bacterial proteins, which lack specific targeting signals, as well as recombinant proteins containing mammalian targeting sequences, i.e. the sequence encoding for the addition of a glycosyl-phosphatidyl inositol (GPI) membrane anchor. Utilizing both HSV1 recombinant and amplicon vectors we demonstrate that while a GPI anchor is able to direct a foreign protein to the plasma membrane, the recombinant protein is targeted mainly to the dendritic, but also to the axonal plasma membrane; i.e. its distribution is not completely polarized. Thus, GPI anchors do not function as dominant polarized targeting signals in neurones, as they do in polarized epithelial cell lines.