Most cases of early-onset torsion dystonia are caused by deletion of GAG in the coding region of the DYT1 gene encoding torsinA. This autosomal dominant neurologic disorder is characterized by abnormal movements, believed to originate from neuronal dysfunction in the basal ganglia of the human brain. The torsins (torsinA and torsinB) are members of the "ATPases associated with a variety of cellular activities" (AAA(+)) superfamily of proteins that mediate chaperone and other functions involved in conformational modeling of proteins, protection from stress, and targeting of proteins to cellular organelles. In this study, the intracellular localization and levels of endogenous torsin were evaluated in rat pheochromocytoma PC12 cells following differentiation and stress. TorsinA, apparent MW 37 kDa, cofractionates with markers for the microsomal/endoplasmic reticulum (ER) compartment and appears to reside primarily within the ER lumen based on protease resistance. TorsinA immunoreactivity colocalizes with the lumenal ER protein protein disulfide isomerase (PDI) and extends throughout neurites. Levels of torsinA did not increase notably in response to nerve growth factor-induced differentiation. None of the stress conditions tested, including heat shock and the unfolded protein response, affected torsinA, except for oxidative stress, which resulted in an increase in the apparent MW of torsinA and redistribution to protrusions from the cell surface. These findings are consistent with a relatively rapid covalent modification of torsinA in response to oxidative stress causing a change in state. Mutant torsinA may interfere with and/or compromise ER functions, especially in dopaminergic neurons, which have high levels of torsinA and are intrinsically vulnerable to oxidative stress.

Herpes simplex virus type I (HSV) typically enters peripheral nerve terminals and then travels back along the nerve to reach the neuronal cell body, where it replicates or enters latency. To monitor axoplasmic transport of HSV, we used the giant axon of the squid, Loligo pealei, a well known system for the study of axoplasmic transport. To deliver HSV into the axoplasm, viral particles stripped of their envelopes by detergent were injected into the giant axon, thereby bypassing the infective process. Labeling the viral tegument protein, VP16, with green fluorescent protein allowed viral particles moving inside the axon to be imaged by confocal microscopy. Viral particles moved 2.2 ؎ 0.26 m͞sec in the retrograde direction, a rate comparable to that of the transport of endogenous organelles and of virus in mammalian neurons in culture. Electron microscopy confirmed that 96% of motile (stripped) viral particles had lost their envelope but retained tegument, and Western blot analysis revealed that these particles had retained protein from capsid but not envelope. We conclude that (i) HSV recruits the squid retrograde transport machinery; (ii) viral tegument and capsid but not envelope are sufficient for this recruitment; and (iii) the giant axon of the squid provides a unique system to dissect the viral components required for transport and to identify the cellular transport mechanisms they recruit.

Novel hybrid vectors, which incorporate critical elements of both herpes simplex virus type 1 (HSV-1) amplicon vectors and adeno-associated virus (AAV) vectors, are able to sustain transgene expression in dividing glioma cells for over 2 weeks. These vectors combine the high infectibility and large transgene capacity of HSV-1 vectors with the potential for episomal amplification and chromosomal integration of AAV vectors. The hybrid vectors contain the HSV-1 origin of DNA replication, oriS, and the DNA cleavage/packaging signal, pac, which allow amplicon replication and packaging in HSV-1 virions. The lacZ reporter gene under control of the CMV IE1 promoter is flanked by AAV inverted terminal repeat (ITR) sequences, which facilitate replication and genomic integration of this cassette in the host cell nucleus. Constructs were generated with or without the AAV rep gene (rep+ and rep-) to assess its importance in extending transgene expression. Expression of Rep proteins was confirmed by Western blot analysis. An HSV-1 amplicon construct containing the reporter gene, but no AAV sequences, was used as a control. Constructs were packaged into HSV-1 virions with or without helper virus and these vector stocks were used to infect human U87 glioma cells in culture. The hybrid vectors supported transgene retention and expression for over 2 weeks, whereas the control amplicon vector lost the transgene after 10 days. Expression was somewhat longer for the rep+ as compared to the rep- hybrid vectors. Toxicity due to the HSV-1 helper virus was eliminated using helper virus-free amplicon vector stocks. Transgene constructs could also be packaged in AAV virions, using AAV and adenovirus or HSV-1 helper functions. These HSV/AAV hybrid vectors should allow long-term, nontoxic gene delivery of DNA constructs to both dividing and nondividing cells.

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