It encodes a small tail-anchored, type II membrane protein. For a long time neglected as a non essential viral product, US9 has recently gained more attention because viruses deleted in the US9 gene show defects in the ability to move in the anterograde direction in the axons and to establish secondary infections in the brains of infected animals. Virus anterograde transport occurs inside vesicles; besides being a constitutive component of transported virions, US9 is present on transport vesicles membrane. The impairment shown by deletion viruses implies that US9 participates in the process of virus egress, and that this effect is dependent on the ability of the protein to directly or indirectly regulate the interaction of the viral particle with the transport machinery. In Pseudo-Rabies Virus the role in transport played by US9 has been extensively investigated and recently visually demonstrated in vivo by Taylor et al.. However, beside the US9 activity related to virus replication and diffusion in the infected host, it is of great interest to understand the molecular features that confer the protein its ability to drive vesicles transport. Localization studies showed that US9 mostly accumulates in Trans Golgi Network, but it is also detected in more peripheral regions of the cell, as well at the plasma membrane, in agreement to the assigned transport task deduced from deletion studies. Starting from the acknowledged role played by US9 in virus transport, we decided to look at US9 stand alone properties using GFP-tagged constructs in a GDC-0199 customer reviews virus-free cellular environment, both in fixed cells and in real time experiments, aimed to investigate if and to which extent US9 properties that in the viral context serve virus transport and infection spread, can be directly ascribed to US9. The results presented here highlight the dynamic behavior of US9, supporting the idea that the viral protein is able to autonomously interact with the cellular transport machinery, in a cell type independent manner. In fact, US9 is always detectable in both proximal and peripheral cellular regions, as well as on the plasma membrane. This ability, which in the viral context supports transport and delivery of viral particles or of its components, is maintained even in the absence of other viral factors. By using truncated forms of the viral protein, we observed that while the US9 trans-membrane domain partially recapitulates the functional behavior of the full length protein, as it is still able to dictate localization of the fused GFP moiety in both cytosolic puncta and at the plasma membrane, it clearly differs from the full length GFP-US9. Notably, the major difference ascribed to the absence of the US9 cytosolic domain is the reduced punctuate staining and the enhanced accumulation of the protein at the plasma membrane. Finally, mutagenesis of key tyrosines and serines in the acidic domain located in the middle of the cytosolic portion of the protein and important for virus transport do not affect US9 behavior, supporting the hypothesis that post-translational modifications represent a tuning system adopted by the virus to regulate cargo loading and, consequently, virion export and delivery; however, and most importantly.