Complex sentence: G protein-coupled receptor 6, also known as GPR6, is a human gene coding for a receptor that gets selectively activated by sphingosine-1-phosphate.
Split into simpler sentences: G protein-coupled receptor 6, also known as GPR6, is a protein which in humans is encoded by the "GPR6" gene. It has been reported that GPR6 is activated by sphingosine-1-phosphate.