Abstract

Nucleotide stimulation of G_q-coupled P2Y receptors expressed in Xenopuslaevis oocytes produces the activation of an endogenous voltage-gated ion channel, previously identified as the transient inward (T_in) channel. Expression of human P2Y₁, human P2Y₂, rat P2Y₆, human P2Y₁₁, or skate P2Y receptors in oocytes resulted in modulation of the voltage dependence and inactivation gating of the channel. Expression of the human P2Y₄ receptor, rat M₁-muscarinic receptor, and human B₁-bradykinin receptor did not alter the properties of the T_in channel. Replacement of the C-terminal domain of the human B₁-bradykinin receptor with the C-terminal domains of either the human P2Y₁ or human P2Y₂receptor resulted in voltage dependence and inactivation-gating properties, respectively, of the T_in channel that were similar to those elicited by the respective native P2Y receptor. Systematic truncation of the C-terminal region of the human P2Y₁ receptor identified a short region responsible for modulation of the T_in channel. This region contains a conserved sequence motif found in all P2Y receptors that modulates the voltage dependence of the T_in channel. Synthetic 20-mer peptides from the C-terminal domains of human P2Y₁ and P2Y₂ receptors produced a shift in the voltage dependence and slowed inactivation gating, respectively, after injection into oocytes expressing human B₁-bradykinin or truncated human P2Y₁ receptors. These results indicate that certain P2Y receptors are capable of modulating the voltage sensitivity and inactivation gating of an endogenous oocyte ion channel through interactions involving the C-terminal region of the receptor. Such modulation of ion channel function could also exist in native mammalian cells that express P2Y receptors.