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Heterotrimeric G‐protein serves as scaffold for Mu‐opioid receptor mediated signal transduction in lipid rafts
Author(s) -
Zhang Lei,
Law PingYee
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a916
Subject(s) - lipid raft , heterotrimeric g protein , adenylyl cyclase , microbiology and biotechnology , g protein , g protein coupled receptor , signal transduction , gs alpha subunit , chemistry , receptor , camp dependent pathway , scaffold protein , biology , biochemistry
Mu‐opioid receptor (MOR) belongs to the G‐protein coupled receptors, which couples specifically to Gi/Go heterotrimeric G proteins. Our recent studies suggest that Gi2 not only is responsible for opioid agonist inhibition of adenylyl cyclase activity, but also performs as a scaffold to recruit the receptor and post‐receptor signaling molecules to form a signaling complex for adenylyl cyclase superactivation after chronic agonist treatment. Our current results show that in neuroblastoma Neuro2A‐MOR (N2AMOR) cells, MOR and Gi2 are both located in lipid rafts fractions, the plasma membrane microdomains that are rich in sphingolipid and cholesterol. Using co‐immunoprecipitation and confocal fluorescent microscopy techniques, MOR and Gi2 are colocalized and interacted with each other in lipid rafts. Disruption of lipid rafts by methyl‐beta‐cyclodextrin causes the loss of colocalization of mu‐receptors and Gi2. More importantly, disruption of lipid rafts also causes the loss of MOR activities, including the inhibition of agonist‐induced intracellular cAMP level and mobilization of the intracellular Ca 2+ . Furthermore these activities can be restored after adding back cholesterol. Taken together, these observations suggest that G‐protein scaffolding and lipid raft localization are essential for the receptor to regulate the signal transduction precisely and efficiently. (Research supported by NIDA grants DA0166774 and DA007339)