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Differential internalization of mammalian and non-mammalian gonadotropin-releasing hormone receptors - Uncoupling of dynamin-dependent internalization from mitogen-activated protein kinase signaling
被引:60
作者:
Hislop, JN
Everest, HM
Flynn, A
Harding, T
Uney, JB
Troskie, BE
Millar, RP
McArdle, CA
[1
]
机构:
[1] Univ Bristol, Res Ctr Neuroendocrinol, Bristol BS2 8HW, Avon, England
[2] MRC, Human Reprod Sci Unit, Edinburgh EH3 9ET, Midlothian, Scotland
[3] Univ Cape Town, Dept Biochem Med, ZA-7925 Observatory, South Africa
关键词:
D O I:
10.1074/jbc.M104542200
中图分类号:
Q5 [生物化学];
Q7 [分子生物学];
学科分类号:
071010 ;
081704 ;
摘要:
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) GnRII-R signaling to ERK 2 is dynamin-dependent and c) this does not reflect a dependence on dynamin-dependent GnRH-R internalization.
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页码:39685 / 39694
页数:10
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