Figure 2.

Bile acid signaling through membrane-bound or nuclear receptors. Certain bile acids can bind the membrane receptors TGR5, S1PR2, and a5B1 integrin. Alternatively, bile acids may exert their effects through nuclear receptors. In order for bile acids to bind nuclear receptors, they need to passively diffuse across the cell membrane or are actively transported by ASBT, NTCP, or OATP. Once inside the cell, bile acids can bind FXR, VDR, PXR, GR, or CAR which facilitates DNA binding and subsequent regulation of transcription. Similar to the membrane bile acid receptors, these nuclear receptors have differential affinity for specific bile acids, which are indicated in this figure.