Activity of hBSEP transporter expressed in human and insect cells

Abstract

Membrane transporters involved in the recycling of bile acids are also very important for the disposition of some drugs in the liver. The opportunity to measure the interaction between transporters such as BSEP (ABCB11) and potential drug candidates is very valuable to the drug development process. Overexpression systems, such as the Sf9 insect platform, have been widely used to monitor most of the ABC efflux transporters of clinical interest. While heterologous expression of the human proteins in insect cell membranes often gives high levels of activity some proteins need the lipid environment of their native cells to achieve optimal activity. Attempts by some researchers to overcome this limitation by supplementing the insect membranes with missing components such as cholesterol have met modest success. Although expression in human‐derived cell lines can be challenging, a relevant platform to predict how a human protein might function in vivo should express the protein in a system that mimics, as close as possible, its native environment. We have compared the activity of hBSEP in inverted vesicles derived from either Sf9 or human embryonic kidney (HEK) cells and found that transporter activity is higher in HEK membrane‐derived vesicles but the overall sensitivity to inhibitors (as indicated by IC50 values) is approximately the same.