Differential internalization of mammalian and non-mammalian gonadotropin-releasing hormone receptors. Uncoupling of dynamin-dependent internalization from mitogen-activated protein kinase signaling

J N Hislop, H M Everest, A Flynn, T Harding, J B Uney, B E Troskie, R P Millar, C A McArdle

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

Desensitization and internalization of G-protein-coupled receptors can reflect receptor phosphorylation-dependent binding of beta-arrestin, which prevents G-protein activation and targets receptors for internalization via clathrin-coated vesicles. These can be pinched off by a dynamin collar, and proteins controlling receptor internalization can also mediate mitogen-activated protein kinase signaling. Gonadotropin-releasing hormone (GnRH) stimulates internalization of its receptors via clathrin-coated vesicles. Mammalian GnRH receptors (GnRH-Rs) are unique in that they lack C-terminal tails and do not rapidly desensitize, whereas non-mammalian GnRH-R have C-terminal tails and, where investigated, do rapidly desensitize and internalize. Using recombinant adenovirus expressing human and Xenopus GnRH-Rs we have explored the relationship between receptor internalization and mitogen-activated protein kinase signaling in HeLa cells with regulated tetracycline-controlled expression of wild-type or a dominant negative mutant (K44A) of dynamin. These receptors were phospholipase C-coupled and had appropriate ligand affinity and specificity. K44A dynamin expression did not alter human GnRH-R internalization but dramatically reduced internalization of Xenopus GnRH-R (and epidermal growth factor (EGF) receptor). Blockade of clathrin-mediated internalization (sucrose) abolished internalization of all three receptors. Both GnRH-Rs also mediated phosphorylation of ERK 2 and for both receptors, this was inhibited by K44A dynamin. The same was true for EGF- and protein kinase C-mediated ERK 2 phosphorylation. ERK 2 phosphorylation was also inhibited by a protein kinase C inhibitor but not affected by an EGF receptor tyrosine kinase inhibitor. We conclude that a) desensitizing and non-desensitizing GnRH-Rs are targeted for clathrin-coated vesicle-mediated internalization by functionally distinct mechanisms, b) GnRH-R signaling to ERK 2 is dynamin-dependent and c) this does not reflect a dependence on dynamin-dependent GnRH-R internalization.
Original languageEnglish
Pages (from-to)39685-94
Number of pages10
JournalThe Journal of Biological Chemistry
Volume276
Issue number43
DOIs
Publication statusPublished - 26 Oct 2001

Keywords

  • Animals
  • Dynamins
  • Endocytosis
  • GTP Phosphohydrolases
  • Humans
  • Inositol Phosphates
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinases
  • Receptors, LHRH
  • Recombinant Proteins
  • Signal Transduction
  • Species Specificity

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