Glial-specific retrovirally mediated gas1 gene expression induces glioma cell apoptosis and inhibits tumor growth in vivo.

We recently reported that the targeted expression of growth arrest specific 1 (Gas1) induces apoptosis in glioma cells. Because the vast majority of gliomas present genetic alterations that reduce their ability to undergo apoptosis, a gene therapy strategy aimed at reinstating apoptotic processes in glioma cells is an interesting approach for the treatment of these tumors. We used a retroviral gene transfer system to transduce C6 glioma cells with a transgene in which the expression of a full-length human gas1 cDNA is under the transcriptional control of a human promoter of the glial fibrillary acidic protein (gfa2). In vitro experiments showed that the retroviral transfer of gas1 significantly reduces the number of viable cells, and induces apoptosis in C6 cells, through the activation of caspase-3. Furthermore, retroviral-mediated transfer of gas1 to gliomas implanted in nude mice induces a significant inhibition of tumor growth, accompanied by increased caspase-3 activation. In the present experiments, we have taken advantage of the property of retrovirus to transfer transgenes exclusively to proliferating cells, together with the use of a glial specific promoter, to selectively target the expression of gas1, a pro-apoptotic gene, to glioma cells.

Human brain synembryn interacts with Gsalpha and Gqalpha and is translocated to the plasma membrane in response to isoproterenol and carbachol.

Heterotrimeric G-proteins transduce signals from heptahelical transmembrane receptors to different effector systems, regulating diverse complex intracellular pathways and functions. In brain, facilitation of depolarization-induced neurotransmitter release for synaptic transmission is mediated by Gsalpha and Gqalpha. To identify effectors for Galpha-proteins, we performed a yeast two-hybrid screening of a human brain cDNA library, using the human Galphas protein as a bait. We identified a protein member of the synembryn family as one of the interacting proteins. Extending the study to other Galpha subunits, we found that Gqalpha also interacts with synembryn, and these interactions were confirmed by in vitro pull down studies and by in vivo confocal laser microscopy analysis. Furthermore, synembryn was shown to translocate to the plasma membrane in response to carbachol and isoproterenol. This study supports recent findings in C. elegans where, through genetic studies, synembryn was shown to act together with Gqalpha regulating neuronal transmitter release. Based on these observations, we propose that synembryn is playing a similar role in human neuronal cells.