| First Author | Marsango S | Year | 2022 |
| Journal | Proc Natl Acad Sci U S A | Volume | 119 |
| Issue | 24 | Pages | e2201103119 |
| PubMed ID | 35671422 | Mgi Jnum | J:326751 |
| Mgi Id | MGI:7311550 | Doi | 10.1073/pnas.2201103119 |
| Citation | Marsango S, et al. (2022) The M1 muscarinic receptor is present in situ as a ligand-regulated mixture of monomers and oligomeric complexes. Proc Natl Acad Sci U S A 119(24):e2201103119 |
| abstractText | The quaternary organization of rhodopsin-like G protein-coupled receptors in native tissues is unknown. To address this we generated mice in which the M1 muscarinic acetylcholine receptor was replaced with a C-terminally monomeric enhanced green fluorescent protein (mEGFP)-linked variant. Fluorescence imaging of brain slices demonstrated appropriate regional distribution, and using both anti-M1 and anti-green fluorescent protein antisera the expressed transgene was detected in both cortex and hippocampus only as the full-length polypeptide. M1-mEGFP was expressed at levels equal to the M1 receptor in wild-type mice and was expressed throughout cell bodies and projections in cultured neurons from these animals. Signaling and behavioral studies demonstrated M1-mEGFP was fully active. Application of fluorescence intensity fluctuation spectrometry to regions of interest within M1-mEGFP-expressing neurons quantified local levels of expression and showed the receptor was present as a mixture of monomers, dimers, and higher-order oligomeric complexes. Treatment with both an agonist and an antagonist ligand promoted monomerization of the M1-mEGFP receptor. The quaternary organization of a class A G protein-coupled receptor in situ was directly quantified in neurons in this study, which answers the much-debated question of the extent and potential ligand-induced regulation of basal quaternary organization of such a receptor in native tissue when present at endogenous expression levels. |
