Expression and purification of human alpha-7 nicotinic acetylcholine receptor extracellular domain in Pichia pastoris

Human alpha-7 nicotinic acetylcholine receptor (alpha-7 nAChR) is an ion channel that plays a significant function in neuronal communication and development. Defects of alpha-7 nAChR could cause plethora of neurologic and psychiatric impairments such as schizophrenia, Alzheimer's, and inflammatory disorders. Hence, alpha-7 nAChR is an interesting candidate for drug development targeting neurological and inflammatory diseases. Therefore, the ability to obtain significant amount of the alpha-7 nAChR extracellular domain is crucial for further biochemical and structural investigations. We constructed a Pichia pastoris yeast strain that secretes the alpha-7 nAChR extracellular domain. The recombinant protein was hyperglycosylated and could be deglycosylated with Endoglycosidase H treatment. Crosslinking experiments suggested that the recombinant protein could form oligomeric states, consistent with the known property of the native alpha-7 nAChR. The optimized expression yield was 4.9 mg/l.