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I am reading papers about heterologous expression systems and I have seen that they are used a lot in neuroscience to studying interactions between proteins that are normally expressed in the brain.

I have seen that in research papers, CHO cells are used as a model cell line to study the interactions between neuronal proteins. This is done through overexpressing a protein of interest that is natively expressed in neurons in CHO cells and investigating interactions of that protein with another protein (that is endogenously expressed in CHO cells but also found in neurons).

However, I was wondering, what are the advantages of using CHO cells instead to study interactions between neuronal proteins instead of a cell culture of neurons? Wouldn't it be more accurate to study interactions between neuronal proteins using cultured neurons instead? Any insights are appreciated.

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  • $\begingroup$ Should depend on the interaction being studied. If the interaction happens within a single cell a cell line should suffice. $\endgroup$
    – Roni Saiba
    Jul 5 at 8:51
  • $\begingroup$ @ceno980 I do not know why your question is being downvoted. I feel this is a genuine question researchers come across when they getting into new arena. $\endgroup$
    – Science123
    Jul 5 at 14:28
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One of the advantages you already stated that depending on protein of interest if it's already expressed in CHO cell line, researchers use that.

Apart from that, this question is more of a general type. I will try my best to logically put down the things.

You are right, it's more appropriate to study proteins using cultured neurons. But, there are many practical factors that may compel us to avoid cultured neurons.

  1. Ease of Culturing cells Its way easier to culture cell lines such as CHO/HEK293/HeLa compared to neurons. Neurons are very sensitive and culturing them needs serious expertise and still, things can get wrong. There are many labs across the world that have dedicated technicians to avoid individual differences between cultures which can topple up experimental results. In contrast, culturing common cell lines doesn't need that level of expertise (relative comparison). Furthermore, for neuronal culture, several serious ethical guidelines need to be followed and require a good amount of funding to set up the facility. In addition, to have neurons develop processes and ready for study generally 10-12 days are required which prolongs the length of study. With common cell lines, you can perform an unlimited number of experiments and get results in a relatively short amount of time.

  2. Ease of expression Sometimes, the endogenous level of expression is not sufficient enough to visualize the interactions. More importantly, you do not have a tool to visualize these endogenously expressed proteins in cultured neurons. At that point Transfection and overexpression comes in handy. Transfection and overexpression in cultured neurons are way more difficult compared to common cell lines such as CHO, HEK, HeLa, etc. The efficiency is very low. It needs serious optimization and still, everything may go in vain. If endogenous expression levels are sufficient enough, knock-in expression is an option. Still, it requires several months to have such knocked-in mice and the success of knock-in is very low with larger proteins such as fluorescent proteins. Indeed new techniques are getting developed such as viral methods etc. Still, they are not well established across the globe. In the case of common cell lines, it's relatively easy to transfect/optimize the conditions to obtain abundant protein of interest for the study.

Thus weighing time, money, expertise, and whether or not cultured neurons absolutely necessary to draw meaningful conclusions generally determine which cells to choose.

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  • $\begingroup$ Thank you for your reply. Regarding your statement: "More importantly, you do not have a tool to visualize these endogenously expressed proteins in cultured neurons." I was wondering, is it not possible permeabilise the cell membranes of the neurons and then use indirect immunofluorescence to detect proteins that are endogenously expressed (even if they are expressed at a very low level)? $\endgroup$
    – ceno980
    Jul 5 at 21:24
  • $\begingroup$ (1/2) Good question.There are some reasons for this.Let me clarify one thing first. Endogenous doesn’t necessarily refer to proteins present inside the cell rather it means ‘natively expressed’.Not always you want to permealize and visualize intracellular proteins. For example 70% of the FDA approved drugs target membrane proteins. Coming back to your exact question,currently we don’t have antibodies for many of the proteins of interest.Cross reactivity,low affinity etc are the common issues with available antibodies. $\endgroup$
    – Science123
    Jul 6 at 15:11
  • $\begingroup$ @ceno980 (2/2)(continued) Therefore you see studies genetically attaching fluorescent proteins/epitope tags to the protein of interest to study/visualize them.Still they are not perfect. That’s a different topic for discussion. $\endgroup$
    – Science123
    Jul 6 at 15:18
  • $\begingroup$ Thank you, for your reply it really helped $\endgroup$
    – ceno980
    Jul 7 at 1:05

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