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Subcellular localization of mu-opioid receptor G(s) signaling

Sumita Chakrabarti1, Andrew Chang, Alan R Gintzler

  • 1Department of Biochemistry, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA.

The Journal of Pharmacology and Experimental Therapeutics
|January 26, 2010
PubMed

Insights

The mu-opioid receptor (MOR) couples with G(s)alpha proteins, a signaling pathway enhanced by caveolae. This study confirms MOR-G(s)alpha functionality and highlights caveolae

Area of Science:

  • Neuropharmacology
  • Cellular Signaling
  • Membrane Biology

Background:

  • The functional coupling of the mu-opioid receptor (MOR) with G(s)alpha proteins has been previously described but remained debated.
  • Caveolae, specialized membrane microdomains, are implicated in various cellular signaling pathways.

Purpose of the Study:

  • To confirm the functional coupling between MOR and G(s)alpha.
  • To investigate the role of caveolae in MOR-mediated G(s)alpha signaling.

Main Methods:

  • Utilized Chinese hamster ovary (CHO) cells expressing MOR (MOR-CHO) and spinal cord membranes.
  • Stimulated MOR with sufentanil and blocked with naloxone.
  • Assessed guanosine 5'-O-(3-[35S]thio)triphosphate binding, G(s)alpha translocation, and co-immunoprecipitation (co-IP) with caveolin-1 and adenylyl cyclase (AC).

Main Results:

  • Sufentanil stimulated G(s)alpha binding to GTP in MOR-CHO membranes, which was blocked by naloxone, confirming MOR-G(s)alpha functionality.
  • MOR activation led to G(s)alpha translocation into Triton-insoluble membrane fractions and enhanced co-IP of G(s)alpha and AC with caveolin-1.
  • Lesser-phosphorylated G(s)alpha, preferentially coupled to MOR, were found concentrated in caveolae.

Conclusions:

  • This study unequivocally demonstrates the functional coupling of MOR with G(s)alpha.
  • Caveolae play a significant role in MOR-mediated G(s)alpha signaling, potentially housing downstream effectors for MOR-G(s)alpha-AC signaling.

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