The sigma 1 receptors are present in monomeric and oligomeric forms in living cells in the presence and absence of ligands

The sigma-1 receptor (S1R) is a membrane 223-amino acid protein that resides in the endoplasmic reticulum and the plasma membrane of some mammalian cells. The S1R is regulated by a various synthetic molecules including (+)-pentazocine, cocaine and haloperidol, and endogenous molecules such as sphingosine, dimethyltryptamine and dehydroepiandrosterone. Ligand regulated protein chaperone functions linked to oxidative stress and neurodegenerative disorders such as ALS and neuropathic pain have been attributed to the S1R. Several client proteins that interact with S1R have been identified including various types of ion channels and G-protein coupled receptors. When S1R constructs containing C-terminal monomeric GFP2 and YFP fusions were co-expressed in COS-7 cells and subjected to FRET spectrometry analysis, monomers, dimers, and higher oligomeric forms of S1R were identified under non-liganded conditions. In the presence of the prototypic S1R agonist, (+)-pentazocine, however, monomers and dimers were the prevailing forms of S1R. The prototypic antagonist, haloperidol, on the other hand, favored higher order S1R oligomers. These data, in sum, indicate that heterologously expressed S1Rs occur in vivo in COS-7 cells in multiple oligomeric forms and that S1R ligands alter these oligomeric structures. We suggest that the S1R oligomerization states may regulate its function(s).

Source: BJ Cell - December 15, 2014 Category: Biochemistry Authors: A K Mishra, T A Mavlyutov, D R Singh, G Biener, J Yang, J A Oliver, A E Ruoho, V Raicu Tags: BJ Biomolecules Source Type: research