CLONING AND EXPRESSION OF THE HUMAN GALANIN RECEPTOR GALR2

Galanin is a peptide hormone which modulates a wide variety of physiol ogical processes, including secretion, muscle contraction, cognitive f unction, the reproductive axis, and feeding. Two galanin receptor subt ypes, GalR1 and GalR2, have been cloned; however, for GalR2 only the r at sequence has been reported in the literature. Our cloning of human GalR2 reveals its amino acid sequence to be 85% identical to rat GalR2 and 39% identical to human GalR1. Binding of [I-125]galanin to the hu man GalR2 receptor transiently expressed in COS-7 cells was saturable (K-d = 0.24 nM +/- 0.06 nM) with a receptor density of 383 +/- 66 fmol /mg protein. Human galanin(1-30) bound with high affinity to the human GalR2 receptor, with a Ki value of 0.86 +/- 0.12 nM. With the identif ication of a second galanin receptor subtype, the specific functions o f human galanin receptor subtypes can now begin to be addressed. (C) 1 998 Academic Press.