Functional properties of an isolated αβ heterodimeric human placenta insulin-like growth factor 1 receptor complex

Stephen M. Feltz, Michael L. Swanson, John A. Wemmie, Jeffrey E. Pessin

Research output: Contribution to journalArticle

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Abstract

Treatment of human placenta membranes at pH 8.5 in the presence of 2.0 mM dithiothreitol (DTT) for 5 min, followed by the simultaneous removal of the DTT and pH adjustment to pH 7.6, resulted in the formation of a functional αβ heterodimeric insulin-like growth factor 1 (IGF-1) receptor complex from the native α2β2 heterotetrameric disulfide-linked state. The membrane-bound αβ heterodimeric complex displayed similar curvilinear 125I-IGF-1 equilibrium binding compared to the α2β2 heterotetrameric complex. Triton X-100 solubilization of the alkaline pH and DTT-pretreated placenta membranes, followed by Bio-Gel A-1.5m gel filtration chromatography, was found to effectively separate the α2β2 heterotetrameric and αβ heterodimeric IGF-1 receptor species. 125I-IGF-1 binding to both the isolated α2β2 heterotetrameric and αβ heterodimeric complexes demonstrated a marked straightening of the Scatchard plots, compared to the placenta membrane-bound IGF-1 receptors, with a 2-fold increase in the high-affinity binding component. Similar to the membrane-bound IFG-1 receptor species, the 125I-IGF-1 binding properties between the α2β2 heterotetrameric and αβ heterodimeric complexes were not significantly different. IGF-1 stimulation of IGF-1 receptor autophosphorylation indicated that the ligand-dependent activation of αβ heterodimeric protein kinase activity occurred concomitant with the reassociation into a covalent α2β2 heterotetrameric state. These data demonstrate that (i) a combination of alkaline pH and DTT treatment of human placenta membranes results in the formation of an αβ heterodimeric IGF-1 receptor complex, (ii) unlike the insulin receptor, high-affinity homogeneous IGF-1 binding occurs in both the α2β2 heterotetrameric and αβ heterodimeric complexes, and (iii) IGF-1-dependent autophosphorylation of the αβ heterodimeric IGF-1 receptor complex correlates with an IGF-1-dependent covalent reassociation into an α2β2 heterotetrameric disulfide-linked state.

Original languageEnglish (US)
Pages (from-to)3234-3242
Number of pages9
JournalBiochemistry
Volume27
Issue number9
StatePublished - 1988
Externally publishedYes

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Somatomedin Receptors
Somatomedins
Dithiothreitol
Placenta
Membranes
Disulfides
Insulin Receptor
Octoxynol
Placenta Growth Factor
Protein Kinases
Gel Chromatography
Gels
Straightening
Ligands
Chromatography

ASJC Scopus subject areas

  • Biochemistry

Cite this

Functional properties of an isolated αβ heterodimeric human placenta insulin-like growth factor 1 receptor complex. / Feltz, Stephen M.; Swanson, Michael L.; Wemmie, John A.; Pessin, Jeffrey E.

In: Biochemistry, Vol. 27, No. 9, 1988, p. 3234-3242.

Research output: Contribution to journalArticle

Feltz, Stephen M. ; Swanson, Michael L. ; Wemmie, John A. ; Pessin, Jeffrey E. / Functional properties of an isolated αβ heterodimeric human placenta insulin-like growth factor 1 receptor complex. In: Biochemistry. 1988 ; Vol. 27, No. 9. pp. 3234-3242.
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