Disordered Motifs and Domains in Cell Control - October 11-15, 2014

Disordered Motifs and Domains in Cell Control

Poster Session I

22-POS Board 22 The Intracellular Domain of the Human Growth Hormone Receptor is Intrinsically Disordered and Interacts with Lipids Characteristic of the Inner Plasma Membrane Leaflet Louise F. Nikolajsen 1 , Gitte W. Haxholm 1 , Andrew J. Brooks 2 , Michael J. Waters 2 , Birthe B. Kragelund 1 . 1 University of Copenhagen, Copenhagen, Denmark, 2 University of Queensland, St. Lucia, Queensland, Australia. The growth hormone receptor (GHR) is a single-pass transmembrane protein belonging to the type I cytokine receptor family. The GHR lacks intrinsic kinase activity and therefore depends on the activity of constitutively associated Janus Kinase 2 (JAK2) for signaling. GHRs exist as pre-formed inactive dimers in the membrane and binding of growth hormone (GH) leads to formation of active ternary 2:1 receptor/hormone complexes. Binding of GH has been shown to induce conformational changes in the extracellular and transmembrane domains leading to separation of the lower transmembrane domains and thereby separation of associated JAK2s. This separation results in release of intermolecular inhibitory interactions between the associated JAK2s, leading to apposition of kinase domains and signal transduction through the JAK-STAT pathway. Whereas numerous structures are available of complexes of the extracellular domain, no structural characterization is available for the intracellular domain (ICD) of the GHR. Using nuclear magnetic resonance (NMR) spectroscopy we show that the ICD of the human growth hormone receptor is intrinsically disordered over its entire length without long-range contacts. We have identified several transiently populated α-helices distributed along the chain, which are separated by extended structures. Using small unilamellar vesicles (SUVs) and NMR spectroscopy we have shown that the membrane proximal part of the GHR-ICD specifically interacts with lipids characteristic of the inner leaflet of the plasma membrane, but not with outer leaflet lipids. The lipid interaction domain (LID) spans 87 residues with three transient helices and has an architecture that is analogous to a similar domain identified in the human prolactin receptor. We propose a role for the LID:membrane interactions in signaling efficiency of the receptor.

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