Kappa but not delta or mu opioid receptors form homodimers at low membrane densities.
Cell Mol Life Sci
; 78(23): 7557-7568, 2021 Dec.
Article
em En
| MEDLINE
| ID: mdl-34657173
ABSTRACT
Opioid receptors (ORs) have been observed as homo- and heterodimers, but it is unclear if the dimers are stable under physiological conditions, and whether monomers or dimers comprise the predominant fraction in a cell. Here, we use three live-cell imaging approaches to assess dimerization of ORs at expression levels that are 10-100 × smaller than in classical biochemical assays. At membrane densities around 25/µm2, a split-GFP assay reveals that κOR dimerizes, while µOR and δOR stay monomeric. At receptor densities < 5/µm2, single-molecule imaging showed no κOR dimers, supporting the concept that dimer formation depends on receptor membrane density. To directly observe the transition from monomers to dimers, we used a single-molecule assay to assess membrane protein interactions at densities up to 100 × higher than conventional single-molecule imaging. We observe that κOR is monomeric at densities < 10/µm2 and forms dimers at densities that are considered physiological. In contrast, µOR and δOR stay monomeric even at the highest densities covered by our approach. The observation of long-lasting co-localization of red and green κOR spots suggests that it is a specific effect based on OR dimerization and not an artefact of coincidental encounters.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Membrana Celular
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Receptores Opioides delta
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Receptores Opioides mu
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Análise de Célula Única
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Imagem Individual de Molécula
Limite:
Animals
Idioma:
En
Ano de publicação:
2021
Tipo de documento:
Article