A partial μ opioid receptor gene was isolated from a human genomic library using a mouse δ opioid receptor cDNA as a probe. Using information from this genomic clone and the published human μ receptor, MOR1 a cDNA was isolated from SK-N-SH mRNA that codes for a variant of the MOR1 mRNA, MOR1A. The presence of MOR1A is also shown in human brain using RT-PCR. MOR1A differs from MOR1 in that the 3′ terminal intron has not been removed. An in-frame termination codon is found four amino acids after the 5′ consensus splice site, making MOR1A eight amino acids shorter than MOR1. Both receptors show similar ligand binding and coupling to cAMP in CHO-K1 cells. The C-terminal differences between MOR1 and MOR1A could have effects on receptor coupling or receptor transport and localization. © 1994.
Bare, L. A., Mansson, E., & Yang, D. (1994). Expression of two variants of the human μ opioid receptor mRNA in SK-N-SH cells and human brain. FEBS Letters, 354(2), 213–216. https://doi.org/10.1016/0014-5793(94)01129-X