Figure 4
From: A novel alternatively spliced isoform of the mu-opioid receptor: functional antagonism
MOR1K couples to Gα s . COS1 cells were transiently transfected with MYC-tagged MOR1 or FLAG-tagged MOR1K constructs. (A) Iimmunoprecipitation was performed with anti-FLAG (raised in rabbit) and anti-MYC (raised in rabbit) antibodies. Immunoblotting was conducted with specific anti-Gα antibodies as described. The MOR1K-FLAG construct was found to couple to Gαs, while the MOR1-MYC construct coupled only to Gαi/o. The exposure time for MOR1K-FLAG experiments were ~2 times longer to see band intensities comparable to MOR1-MYC. (B) Consistent with Gαs binding to the MOR1K isoform, morphine-mediated increases in Ca2+ levels were not prevented by pre-treatment of MOR1K expressing cells with PTX (100 ng/ml for 15min).