Expression of opioid and anti-opioid receptors in Chinese hamster ovary cells after exposure to dimethyl sulfoxide

Functional and structural studies on G-protein-coupled receptors (GPCRs) at molecular levels require producing and purifying high levels of receptors, and recombinant mammalian cell expression systems constitute the best systems to obtain receptors resembling those expressed in natural environments. In the course of increasing GPCR expression in Chinese hamster ovary (CHO) cells, we have expressed mu (μ)- and kappa (κ)-opioid receptors and neuropeptide FF(1) and FF(2) receptors (NPFF(1) and NPFF(2), respectively) in dimethyl sulfoxide. This treatment did not modify the affinity (K(d)) for any receptor, but a significant increase in functional expression levels was observed for all receptors with the noticeable exception of NPFF(1).