Amino-Terminal Processing of the Human Cannabinoid Receptor 1

The human cannabinoid receptor 1 (CB1), a G protein-coupled receptor (GPCR), translocates its long amino-terminal (N-terminal) domain across the endoplasmic reticulum (ER) membrane in a C-to-N terminal direction. Using the Semliki Forest virus (SFV) expression system, CB1 was expressed in baby hamster kidney (BHK) cells. It was found that a large fraction of the CB1 molecules were N-terminally truncated prior to ER translocation. Truncation was fast and independent of the proteasome. It is concluded that the truncation process might be a way to create a novel type of CB1.