Left-Handed Dimer of EphA2 Transmembrane Domain: Helix Packing Diversity among Receptor Tyrosine Kinases

Abstract

The Eph receptor tyrosine kinases and their membrane-bound ephrin ligands control a diverse array of cell-cell interactions in the developing and adult organisms. During signal transduction across plasma membrane, Eph receptors, like other receptor tyrosine kinases, are involved in lateral dimerization and subsequent oligomerization presumably with proper assembly of their single-span transmembrane domains. Spatial structure of dimeric transmembrane domain of EphA2 receptor embedded into lipid bicelle was obtained by solution NMR, showing a left-handed parallel packing of the transmembrane helices (535-559)(2). The helices interact through the extended heptad repeat motif L(535)X(3)G(539)X(2)A(542)X(3)V(546)X(2)L(549) assisted by intermolecular stacking interactions of aromatic rings of (FF(557))(2), whereas the characteristic tandem GG4-like motif A(536)X(3)G(540)X(3)G(544) is not used, enabling another mode of helix-helix association. Importantly, a similar motif AX(3)GX(3)G as was found is responsible for right-handed dimerization of transmembrane domain of the EphA1 receptor. These findings serve as an instructive example of the diversity of transmembrane domain formation within the same family of protein kinases and seem to favor the assumption that the so-called rotation-coupled activation mechanism may take place during the Eph receptor signaling. A possible role of membrane lipid rafts in relation to Eph transmembrane domain oligomerization and Eph signal transduction was also discussed.

Hydrophobic Matching Controls the Tilt and Stability of the Dimeric Platelet-derived Growth Factor Receptor (PDGFR) β Transmembrane Segment

“…The N-and C-terminal regions are disordered due to a lack of 13 C-detected NOEs. 15 N relaxation spectroscopy corroborated that the C terminus from Lys-527 onwards is highly flexible (supplemental Fig. S2C).…”

“…Liquid-state NMR Spectroscopy-Triple-resonance experiments for assignment and 13 C NOESY experiments were recorded on 1 mM uniformly 15 N-labeled or 15 N 13 C-labeled PDGFR␤-TM peptide in 200 mM deuterated DPC micelles (Bruker Avance 600 spectrometer equipped with a TBI tripleresonance probe head). Intermonomer NOEs were acquired from a three-dimensional 13 C-filtered 13 C-edited NOESY measured on a 1:1 mixture of uniformly 15 N 13 C-labeled and unlabeled peptide dissolved in D 2 O (Bruker Avance 900 spectrometer).…”

“…Recent structural studies on the isolated TM helices of ErbB2, EphA1, EphA2, ErbB3, and the heterodimer ErbB1/ ErbB2 showed that the TM helices, at least in these systems, dimerize in two different ways: either right-handed parallel or left-handed coiled-coil ␣-helical dimers (12)(13)(14)(15)(16)(17). Ambiguity remains about what governs the arrangement in either of the two conformations or whether both conformations are relevant for activation and may in fact represent different activation states for a given RTK dimer.…”

“…Ambiguity remains about what governs the arrangement in either of the two conformations or whether both conformations are relevant for activation and may in fact represent different activation states for a given RTK dimer. Based on the observation that RTK activation often occurs in special plasma membrane compartments, called microdomains (18), Arseniev and co-workers suggested that the lipid environment may control the dimerization mode (15).…”

Dimeric structure of transmembrane domain of amyloid precursor protein in micellar environment

“…1 H, 13 1 H/ 13 C-TOCSY-HSQC, 13 C-and 15 N-edited NOESY-HSQC (recorded on 600 and 800 MHz spectrometers, respectively). To characterize intramolecular dynamics the effective rotation correlation times s R were calculated for individual amide groups of 15 N-labeled APPjmtm from the ratio of transverse and longitudinal 15 Nrelaxation rates as described in [12]. Exchange rates between water and H N protons were analyzed by detection of peaks in CLEANEX spectrum [11] recorded for 15 N-labeled APPjmtm sample, and observed cross-peaks were treated as an indication of water exposed amide groups.…”