Differential coupling of 5-HT(1) receptors to G proteins of the G(i) family

Br J Pharmacol. 2002 Aug;136(7):1072-8. doi: 10.1038/sj.bjp.0704809.

Abstract

1: Since all 5-HT(1) receptors couple to G(i)-type G proteins and inhibit adenylyl cyclase, the functional significance of five distinct subtypes of 5-HT(1) receptors has been unclear. 2: In previous studies we have used transfected cells to demonstrate that 5-HT(1B) receptors can couple more efficiently than 5-HT(1A) receptors to activation of extracellular signal-regulated kinase (ERK) and to inhibition of adenylyl cyclase. These findings suggested the possibility that individual 5-HT(1) receptors differentially couple to isoforms of G(ialpha). 3: In the present study we utilized a model system in which pertussis toxin resistant forms of human G(ialpha1), G(ialpha2), and G(ialpha3) were used to directly compare the coupling of human 5-HT(1A), 5-HT(1B), and 5-HT(1D) receptors to each G(ialpha) in transfected human HeLa cells. 4: 5-HT(1A) receptors displayed a preference for G(ialpha1) and G(ialpha2), relative to G(ialpha3). Pertussis toxin resistant forms of G(ialpha1), G(ialpha2), and G(ialpha3) rescued 73%, 76%, and 44%, respectively, of the ERK activation stimulated by 5-HT in the absence of pertussis toxin. 5: In contrast, pertussis toxin resistant forms of G(ialpha1), G(ialpha2), and G(ialpha3) rescued 32%, 118%, and 35% of 5-HT(1B) receptor-stimulated activity, respectively, indicating that 5-HT(1B) receptors coupled primarily through G(ialpha2). A similar preference for G(ialpha2) was found in studies of the 5-HT(1D) receptor, where toxin resistant G(ialpha1), G(ialpha2), and G(ialpha3) rescued 30%, 70%, and 40% of activity, respectively. 6: In conclusion, the observed differential coupling of 5-HT(1) receptors to isoforms of G(ialpha), provides additional evidence for our previous findings that the subtypes of 5-HT(1) receptors exhibit similar, but distinct, functions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenylyl Cyclases / metabolism
  • Enzyme Activation
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism*
  • HeLa Cells
  • Humans
  • Immunoblotting
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases / metabolism
  • Pertussis Toxin / pharmacology
  • Receptor, Serotonin, 5-HT1B
  • Receptor, Serotonin, 5-HT1D
  • Receptors, Serotonin / genetics
  • Receptors, Serotonin / metabolism*
  • Receptors, Serotonin, 5-HT1
  • Transfection

Substances

  • HTR1B protein, human
  • Receptor, Serotonin, 5-HT1B
  • Receptor, Serotonin, 5-HT1D
  • Receptors, Serotonin
  • Receptors, Serotonin, 5-HT1
  • Pertussis Toxin
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • GTP-Binding Protein alpha Subunits, Gi-Go
  • Adenylyl Cyclases