Hi Abhilasha,

I may make a difference. I found that HEK293 cells do not have a chaperone protein for alpha7 nAChRs and that I needed to co-transfect that protein for adequate expression. On the other hand, the alpha4 and beta2 subunits were expressed with no apparent problems. I do not know if the muscle type subunits would pose a problem or not in CHO cells or fibroblasts. However, knowing that expression levels are dependent on the host cell and the type of nAChR subunit, it would be very wise to test for them for function. Alternatively, you could use SH-EP1 cells which do not naturally express functional nAChRs (look up papers from the lab of Ronald Lukas). These have been very useful as a heterologous expression system for functional studies. I have used them for a couple of studies of receptor trafficking using fluorescently-tagged nAChR subunits and been pleased with them.

Dear Abhilasha,

Yes, different host cell backgrounds theoretically can affect functioning of the same ion channel in numerous aspects, including gating, kinetics, expression levels etc. I am not sure of any consistent study methodically investigating this aspect. I can give just one example from the top of my mind: pharmacology of Nav1.2 channels expressed in Xenopus oocytes, when tested by state-dependent blockers, is right-hand shifted by a few orders of magnitude as compared to channels expressed in HEK-293 cells or native neuronal channels.

In my lab, we were using distinct cell backgrounds for expression only if we encountered problems like poor level of expression, poor cell health in culture, poor stability of recordings etc.

To my mind, it makes more sense to find appropriate NATIVE cells expressing same channel and make side-by-side comparison of pharmacology of surrogate expressing systems with native ones. This approach will validate your surrogate system and make you comfortable to run pharmacological studies with it.

Best wishes.

Victor

Hi Abhilasha,

I agree with both Teresa and Victor, and they both raised important points. In my experience I have always noticed difference in responses, as I think it was primarily due to intrinsic membrane and handling properties of individual cells.

best wishes,

Refik

Another issue is that there are differences in adaptor protein, kinase, and native channel expression that can significantly influence kinetics and trafficking of the channel of interest.  

Kristal