How broad are the conclusions that one can make from a heterologous expression experiment? I am studying whether a neural protein regulates the activity of the protein GSK3. I am using heterologous expression systems where I am overexpressing the neural protein in CHO cells (via transfection) to see if it affects the levels of GSK3 in transfected cells vs controls. I am interested in seeing whether the neural protein regulates the activity of GSK3, and I have found that the levels of GSK3 are higher in the transfected cells vs control. But as I am using CHO cells as a model system, how broad are the conclusions that I can draw from this experiment? For example, will I be able to generalise what I found to neurons, or hypothesise that the same thing that I observed in this experiment occurs in neurons? Any insights are appreciated.

GSK3 is interesting because as a kinase, it is itself regulated by its phosphorylation status (particularly by Akt in neurons). Therefore, more protein does not necessarily mean more activity. For example from E13.5 to E15.5 GSK3 levels do not change but activity steadily increases. Hence if you increase GSK3 levels in neurons, it may not mean that downstream effects would change substantially, so I think although promising the _in vivo_ effects may be hard to deduce from this experiment. If you see similar effects in _in vitro_ neurons, you can be a bit more confident of potentially seeing similar effects with _in utero_ electroporation _in vivo_