Vol. 288, Issue 1, 232-238, January 1999

G_L1 (G₁₄) Couples the Opioid Receptor-Like₁ Receptor to Stimulation of Phospholipase C¹

Lisa Y. Yung, Sushma A. Joshi, Robbie Y.K. Chan, Joy S.C. Chan, Gang Pei and Yung H. Wong

Department of Biology and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Kowloon, Hong Kong, China (L.Y.Y., S.A.J., R.Y.K.C., J.S.C.C., Y.H.W.); and Shanghai Institute of Cell Biology, Chinese Academy of Sciences, Shanghai, China (G.P.)

In most tissues and cells the opioid receptor-like (ORL₁) receptor regulates effectors primarily through the pertussis toxin (PTX)-sensitive guanine nucleotide-binding regulatory proteins (G proteins) G_i/G_o. Many G_i-coupled receptors possess additional capability to interact with one or more PTX-insensitive G proteins. Using the -induced stimulation of type 2 adenylyl cyclase as a readout, we screened the ability of ORL₁ receptor to interact with a panel of PTX-insensitive G proteins. In the presence of PTX, activation of the ORL₁ receptor resulted in the stimulation of type 2 adenylyl cyclase only in HEK 293 cells coexpressing the  subunit of G_z, G₁₂, G₁₄, or G₁₆, but not in cells coexpressing G₁₁, G₁₃, or G_q. Coupling to both G_z and G₁₆ was expected because close relatives of the ORL₁ receptor, the opioid receptors, are known to couple productively to these G proteins. ORL₁ receptor coupling to either G₁₂ or G₁₄ has not been demonstrated. As predicted by the type 2 adenylyl cyclase assays, activation of the ORL₁ receptor resulted in the formation of inositol phosphates in COS-7 cells transiently cotransfected with G₁₄. The ORL₁ receptor-mediated stimulation of phospholipase C was found to be G₁₄ dependent, agonist dose dependent, ligand selective, and PTX insensitive. We conclude that G₁₄ can link the ORL₁ receptor to regulation of phopholipase C.