Real-time Kinetic Measurements of the Interactions between Lactogenic Hormones and Prolactin-Receptor Extracellular Domains from Several Species Support the Model of Hormone-induced Transient Receptor Dimerization

doi:10.1074/jbc.271.40.24482

Real-time Kinetic Measurements of the Interactions between Lactogenic Hormones and Prolactin-Receptor Extracellular Domains from Several Species Support the Model of Hormone-induced Transient Receptor Dimerization*

From the ^‡ Institute of Biochemistry, Food Science and Nutrition, and
^″ Department of Soil Science, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel, the
^∥ Medizinische Klinik, Klinikum Innenstadt, Ludwig-Maximilians-Universitat, Munchen, Federal Republic of Germany,
^¶ Unite de Virologie et Immunologie Moleculaire, and
^‴ Unite d'Endocrinologie Moleculaire, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas Cedex, France

^§ To whom correspondence should be addressed:
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agriculture, The Hebrew University of Jerusalem, P.O.B. 12, Rehovot 76100, Israel.
Tel.: 972-89-481324; Fax: 972-89-476189; E-mail: GERTLER{at}AGRI.HUJI.AC.IL

Abstract

Interactions of recombinant soluble prolactin receptors-extracellular domains (PRLR-ECDs) from rabbit, rat, and cow and human growth hormone receptor ECD with immobilized human growth hormone, several prolactins, and bovine placental lactogen were studied utilizing surface plasmon resonance. This method enables real-time kinetic measurements of the interactions and calculations of kinetic constants and of the stoichiometry of interaction, even in cases where only transient interactions occur. In contrast to gel filtration or crystallographic studies, where in most cases the interaction of PRLR-ECDs with various lactogenic hormones indicated formation of 1:1 complexes, our surface plasmon resonance experiments indicated in all cases the transient formation of a 2:1 complex. In most of the interactions the 2:1 complex was very unstable and underwent rapid dissociation to a 1:1 complex. This situation was particularly characteristic of homologous interactions involving hormone and receptor from the same species and was mainly attributed to increased dissociation constants. We suggest that as in the case of growth hormone PRLR activation occurs via hormone-induced transient homodimerization of the receptor, lasting only a few seconds, and that this may be sufficient to initiate the biological signal. Once the signal is initiated, the receptor dimer is no longer required. Its rapid dissociation to a 1:1 complex or to its components may even be advantageous in that it permits activation of additional receptors.

Footnotes

↵* This research was supported by a grant from the Ministry of Science and Technology, Israel, and the French Ministry of Research and Technology Grant 4425-1-92. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

PRL

prolactin

PRLR-ECD

prolactin receptor-extracellular domain

GHR-ECD

growth hormone receptor-extracellular domain

GH

growth hormone

PL

placental lactogen

h

human

b

bovine

o

ovine

r

rat

rb

rabbit

mAbs

monoclonal antibodies

NHS

N-hydroxysuccinimide

EDC

N-ethyl-N′-(3-diethylaminopropyl) carbodiimide

RU

resonance unit.
↵² A. Gertler, J. Grosclaude, C. J. Strasburger, S. Nir, and J. Djiane, unpublished observations.
↵³ C. J. Strasburger, unpublished data.
↵⁴ K. Pearce and J. A. Wells, personal communication.
- Received June 5, 1996.
- Revision received July 16, 1996.