Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The identities of heterotrimeric G proteins that can interact with the mu-opioid receptor were investigated by alpha-azidoanilido[32P]GTP labeling of alpha subunits in the presence of opioid agonists in Chinese hamster ovary (CHO)-MORIVA3 cells, a CHO clone that stably expressed mu-opioid receptor cDNA (MOR-1). This clone expressed 1.01 x 10(6) mu-opioid receptors per cell and had higher binding affinity and potency to inhibit adenylyl cyclase for the mu-opioid-selective ligands [D-Ala2,N-MePhe4, Gly-ol]-enkephalin and [N-MePhe3,D-Pro4]-morphiceptin, relative to the delta-selective opioid agonist [D-Pen2,D-Pen5]-enkephalin or the kappa-selective opioid agonist U-50,488H. mu-Opioid ligands induced an increase in alpha-azidoanilido[32P]GTP photoaffinity labeling of four G alpha subunits in this clone, three of which were identified as Gi3 alpha, Gi2 alpha, and Go2 alpha. The same pattern of simultaneous interaction of the mu-opioid receptor with multiple G alpha subunits was also observed in two other clones, one expressing about three times more and the other 10-fold fewer receptors as those expressed in CHO-MORIVA3 cells. The opioid-induced increase of labeling of these G proteins was agonist specific, concentration dependent, and blocked by naloxone and by pretreatment of these cells with pertussis toxin. A greater agonist-induced increase of alpha-azidoanilido[32P]GTP incorporation into Gi2 alpha (160-280%) and Go2 alpha (110-220%) than for an unknown G alpha (G? alpha) (60%) or Gi3 alpha (40%) was produced by three different mu-opioid ligands tested. In addition, slight differences were also found between the ability of various mu-opioid agonists to produce half-maximal labeling (ED50) of any given G alpha subunit, with a rank order of Gi3 alpha > Go2 alpha > Gi2 alpha = G? alpha. In any case, these results suggest that the activated mu-opioid receptor couples to four distinct G protein alpha subunits simultaneously.
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PMID:Expression of the mu-opioid receptor in CHO cells: ability of mu-opioid ligands to promote alpha-azidoanilido[32P]GTP labeling of multiple G protein alpha subunits. 776 33

Naloxone benzoylhydrazone (NalBzoH) is a potent mu antagonist in vivo. In a cell line stably transfected with MOR-1 (CHO/MOR-1), NalBzoH also was an antagonist when examined in adenylyl cyclase studies. In binding studies, it displayed high affinity for the mu receptor, confirming its earlier characterization in brain membranes. In competition studies under equilibrium conditions, NalBzoH and diprenorphine both retained their potency in the presence of the stable GTP analog 5'-guanylylimidophosphate, consistent with their mu antagonist properties, whereas the agonist DAMGO showed more than a 3-fold loss of affinity. The dissociation of 3H-diprenorphine was monophasic. However, kinetic studies revealed biphasic dissociations for both 3H-NalBzoH and 3H-DAMGO. The slow component of 3H-NalBzoH dissociation, corresponding to the higher affinity state, was dependent on coupling to G-proteins. It is selectively abolished by guanine nucleotides, leaving only the rapid dissociation phase. Furthermore, the slow dissociation component is eliminated by treatment of the cells with pertussis toxin, but not cholera toxin. In conclusion, NalBzoH is an unusual opioid. Functionally it is an antagonist, a classification consistent with its equilibrium binding in the presence of guanine nucleotides. Yet, kinetic studies reveal that it labels a G-protein coupled state of the receptor with high affinity.
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PMID:3H-naloxone benzoylhydrazone binding in MOR-1-transfected Chinese hamster ovary cells: evidence for G-protein-dependent antagonist binding. 965 82