The oligomeric states of the purified sigma-1 receptor are stabilized by ligands.
Sigma-1 receptor (S1R) is a mammalian member of the ERG2 and sigma-1 receptor-like protein family (pfam04622). It has been implicated in drug addiction and many human neurological disorders, including Alzheimer and Parkinson diseases and amyotrophic lateral sclerosis. A broad range of synthetic small molecules, including cocaine, (+)-pentazocine, haloperidol, and small endogenous molecules such as N,N-dimethyltryptamine, sphingosine, and steroids, have been identified as regulators of S1R. However, the mechanism of activation of S1R remains obscure. Here, we provide evidence in vitro that S1R has ligand binding activity only in an oligomeric state. The oligomeric state is prone to decay into an apparent monomeric form when exposed to elevated temperature, with loss of ligand binding activity. This decay is suppressed in the presence of the known S1R ligands such as haloperidol, BD-1047, and sphingosine. S1R has a GXXXG motif in its second transmembrane region, and these motifs are often involved in oligomerization of membrane proteins. Disrupting mutations within the GXXXG motif shifted the fraction of the higher oligomeric states toward smaller states and resulted in a significant decrease in specific (+)-[(3)H]pentazocine binding. Results presented here support the proposal that S1R function may be regulated by its oligomeric state. Possible mechanisms of molecular regulation of interacting protein partners by S1R in the presence of small molecule ligands are discussed.
From the Transmembrane Protein Center.
Katarzyna A
KA
Gromek
From the Transmembrane Protein Center.
Fabian P
FP
Suchy
From the Transmembrane Protein Center.
Hannah R
HR
Meddaugh
From the Transmembrane Protein Center.
Russell L
RL
Wrobel
Departments of Biochemistry and.
Loren M
LM
LaPointe
Neuroscience, University of Wisconsin-Madison, Madison, Wisconsin 53706.
Uyen B
UB
Chu
From the Transmembrane Protein Center.
John G
JG
Primm
Neuroscience, University of Wisconsin-Madison, Madison, Wisconsin 53706 aeruoho@wisc.edu.
Arnold E
AE
Ruoho
Departments of Biochemistry and.
Alessandro
A
Senes
From the Transmembrane Protein Center, Departments of Biochemistry and bgfox@biochem.wisc.edu.
Brian G
BG
Fox
D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D000818:Animals; D003432:Cross-Linking Reagents; D006168:Guinea Pigs; D006220:Haloperidol / Q000378:metabolism; D006801:Humans; D008024:Ligands; D058619:Maltose-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010423:Pentazocine / Q000378:metabolism; D055503:Protein Multimerization; D055550:Protein Stability; D017480:Receptors, sigma / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000097605:Sigma-1 Receptor
D003432:Cross-Linking Reagents; D006220:Haloperidol; D008024:Ligands; D058619:Maltose-Binding Proteins; D010423:Pentazocine; D017480:Receptors, sigma; D011993:Recombinant Fusion Proteins; D000097605:Sigma-1 Receptor
GXXXG Motif; Ligand-binding Protein; Membrane Protein; Protein-Protein Interaction; Signal Transduction; σ Receptor