Analyzing the validity of GalR1 and GalR2 antibodies using knockout mice

G-protein-coupled receptors (GPCRs) comprise the largest family of cell surface receptors and are the major drug targets for the treatment of various human diseases. The lack of sensitive and selective antibodies capable of recognizing endogenous GPCRs, however, hampers the progress of research on this class of receptors. GalR1 through GalR3, GPCRs for the neuropeptide galanin, are potential drug targets for seizure, Alzheimer's disease, depression and anxiety, as well as pain and metabolic syndrome; therefore, determining the cellular and subcellular localization of galanin receptors is of high interest. Several Antibodies raised against galanin receptors are currently available from commercial or academic sources. We have tested several antibodies to GalR1 and GalR2 on tissues from respective knockout mice. Unexpectedly, the immunoreactivity patterns are the same in wild-type and in knockout mice, suggesting that current GalR1 and GalR2 antibodies, under standard immunodetection conditions, might not be suitable for mapping the receptors. These findings argue for taking precaution when using antibodies to galanin receptors.