The arginine of the DRY motif in transmembrane segment III functions as a balancing micro-switch in the activation of the β2-adrenergic receptor

TY - JOUR

T1 - The arginine of the DRY motif in transmembrane segment III functions as a balancing micro-switch in the activation of the β2-adrenergic receptor

AU - Hansen, Louise Valentin

AU - Groenen, Marleen

AU - Nygaard, Rie

AU - Frimurer, Thomas M

AU - Holliday, Nicholas D

AU - Schwartz, Thue W

PY - 2012/9/14

Y1 - 2012/9/14

N2 - Recent high resolution x-ray structures of the β2-adrenergic receptor confirmed a close salt-bridge interaction between the suspected micro-switch residue ArgIII:26 (Arg3.50) and the neighboring AspIII:25 (Asp3.49). However, neither the expected "ionic lock" interactions between ArgIII:26 and GluVI:-06 (Glu6.30) in the inactive conformation nor the interaction with TyrV:24 (Tyr5.58) in the active conformation were observed in the x-ray structures. Here we find through molecular dynamics simulations, after removal of the stabilizing T4 lysozyme, that the expected salt bridge between ArgIII:26 and GluVI:-06 does form relatively easily in the inactive receptor conformation. Moreover, mutational analysis of GluVI:-06 in TM-VI and the neighboring AspIII:25 in TM-III demonstrated that these two residues do function as locks for the inactive receptor conformation as we observed increased G(s) signaling, arrestin mobilization, and internalization upon alanine substitutions. Conversely, TyrV:24 appears to play a role in stabilizing the active receptor conformation as loss of function of G(s) signaling, arrestin mobilization, and receptor internalization was observed upon alanine substitution of TyrV:24. The loss of function of the TyrV:24 mutant could partly be rescued by alanine substitution of either AspIII:25 or GluVI:-06 in the double mutants. Surprisingly, removal of the side chain of the ArgIII:26 micro-switch itself had no effect on G(s) signaling and internalization and only reduced arrestin mobilization slightly. It is suggested that ArgIII:26 is equally important for stabilizing the inactive and the active conformation through interaction with key residues in TM-III, -V, and -VI, but that the ArgIII:26 micro-switch residue itself apparently is not essential for the actual G protein activation.

AB - Recent high resolution x-ray structures of the β2-adrenergic receptor confirmed a close salt-bridge interaction between the suspected micro-switch residue ArgIII:26 (Arg3.50) and the neighboring AspIII:25 (Asp3.49). However, neither the expected "ionic lock" interactions between ArgIII:26 and GluVI:-06 (Glu6.30) in the inactive conformation nor the interaction with TyrV:24 (Tyr5.58) in the active conformation were observed in the x-ray structures. Here we find through molecular dynamics simulations, after removal of the stabilizing T4 lysozyme, that the expected salt bridge between ArgIII:26 and GluVI:-06 does form relatively easily in the inactive receptor conformation. Moreover, mutational analysis of GluVI:-06 in TM-VI and the neighboring AspIII:25 in TM-III demonstrated that these two residues do function as locks for the inactive receptor conformation as we observed increased G(s) signaling, arrestin mobilization, and internalization upon alanine substitutions. Conversely, TyrV:24 appears to play a role in stabilizing the active receptor conformation as loss of function of G(s) signaling, arrestin mobilization, and receptor internalization was observed upon alanine substitution of TyrV:24. The loss of function of the TyrV:24 mutant could partly be rescued by alanine substitution of either AspIII:25 or GluVI:-06 in the double mutants. Surprisingly, removal of the side chain of the ArgIII:26 micro-switch itself had no effect on G(s) signaling and internalization and only reduced arrestin mobilization slightly. It is suggested that ArgIII:26 is equally important for stabilizing the inactive and the active conformation through interaction with key residues in TM-III, -V, and -VI, but that the ArgIII:26 micro-switch residue itself apparently is not essential for the actual G protein activation.

KW - Alanine

KW - Amino Acid Motifs

KW - Animals

KW - Arginine

KW - Arrestin

KW - CHO Cells

KW - COS Cells

KW - Cell Membrane

KW - Cercopithecus aethiops

KW - Cricetinae

KW - GTP-Binding Proteins

KW - Gene Silencing

KW - Models, Molecular

KW - Molecular Dynamics Simulation

KW - Mutagenesis, Site-Directed

KW - Protein Binding

KW - Receptors, Adrenergic, beta-2

KW - Structure-Activity Relationship

U2 - 10.1074/jbc.M112.348565

DO - 10.1074/jbc.M112.348565

M3 - Journal article

C2 - 22843684

SN - 0021-9258

VL - 287

SP - 31973

EP - 31982

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

IS - 38

ER -