Activation of the Luteinizing Hormone/Choriogonadotropin Hormone Receptor Promotes ADP Ribosylation Factor 6 Activation in Porcine Ovarian Follicular Membranes

Lisa M. Salvador, Sutapa Mukherjee, Richard A. Kahn, Marilyn L.G. Lamm, Asgerally T. Fazleabas, Evelyn T. Maizels, Marie France Bader, Heidi Hamm, Mark M. Rasenick, James E. Casanova, Mary Hunzieker-Dunn*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

Previously we demonstrated in a cell-free ovarian follicular plasma membrane model that agonist-dependent desensitization of the luteinizing hormone/choriogonadotropin receptor (LH/CG R) is GTP-dependent, mimicked by the addition of ADP-ribosylation factor (ARF) nucleotide binding site opener, which acts as a guanine nucleotide exchange factor for ARFs 1 and 6, and selectively inhibited by synthetic N-terminal ARF6 peptides. We therefore sought direct evidence that activation of the LH/CG R promotes activation of ARF1 and/or ARF6. Using a classic ARF activation assay, the cholera toxin-catalyzed ADP-ribosylation of Gαs, results show that LH/CG R activation stimulates an ARF protein by a brefeldin A-independent mechanism. Synthetic N-terminal inhibitory ARF6 but not ARF1 peptide blocks LH/CG R-stimulated ARF activity. LH/CG R activation also promotes the binding of a photoaffinity GTP analog to a protein that migrates on one- and two-dimensional polyacrylamide gel electrophoresis with ARF6. These results suggest that ARF6 is the predominant ARF activated by the LH/CG R. To activate ARF6, the LH/CG R does not appear to signal through the C-terminal regions of Gαi or Gαq or through the second or third intracellular loops or the N terminus of the cytoplasmic tail of the LH/CG R. Although exogenous recombinant ARNO promotes only a small increase in ARF6 activation in the presence of activated LH/CG R, hCG-stimulated ARF6 activation is reduced to basal levels by catalytically inactive ARF nucleotide binding-site opener. These results provide direct evidence that LH/CG R activation leads to the activation of membrane-delimited ARF6.

Original languageEnglish (US)
Pages (from-to)33773-33781
Number of pages9
JournalJournal of Biological Chemistry
Volume276
Issue number36
DOIs
StatePublished - Sep 7 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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