Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Kudlacek, O; Waldhoer, M; Kassack, MU; Nickel, P; Salmi, JI; Freissmuth, M; Nanoff, C.
Biased inhibition by a suramin analogue of A1-adenosine receptor/G protein coupling in fused receptor/G protein tandems: the A1-adenosine receptor is predominantly coupled to Goalpha in human brain.
Naunyn Schmiedebergs Arch Pharmacol. 2002; 365(1):8-16
Doi: 10.1007/s00210-001-0493-y
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- Co-Autor*innen der Med Uni Graz
- Waldhoer Maria
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- Abstract:
- The interface between receptors and G proteins can be considered as a drug target. Various classes of low molecular weight inhibitors have been identified that block the ability of receptors to interact with G proteins (e.g. peptides, suramin analogues and amphiphilic cations). Here we have tested if there are compounds that differentially affect the interaction of one receptor with two different (related) G protein alpha-subunits. Fusion proteins comprising the human A1-adenosine receptor and Galphai-1 (A1/Galphai-1) or Galphao (A1/Galphao) were expressed in HEK293 cells. Suramin analogues were screened for their ability to differentially affect high affinity binding of the agonist (-) N6-3-[125I](iodo-4-hydroxyphenylisopropyl) adenosine (IHPIA). One compound [NF326 = 8,8'-(carbonylbis-(imino-3,1-phenylenecarbonylimino))bis-(1-naphthol-3,6-disulfonic acid, disodium salt)] was identified that inhibited high affinity agonist binding to the fusion protein A1/Galphai-1 but modestly enhanced binding of IHPIA to A1/Galphao. This action was specific because NF326 did not affect antagonist binding to either fusion protein. In addition, it was unrelated to a difference in affinity of the receptor for the G protein fusion moiety because the stability of ternary complexes formed by IHPIA + A1/Galphai-1 and IHPIA + A1/Galphao) is comparable and because lowering the affinity of the receptor for the G protein (by introducing point mutations at cys351 of Galphai-1) enhanced the uncoupling effect of NF326. Finally, NF326 did not discriminate between a fusion protein comprising the alpha2A-adrenoceptor and Galphai-1 (alpha2A)/Galphai-1) or Galphao-1 (alpha2A)/Galphao-1); binding of the agonist [3H]UK14304 (bromoxidine) to both fusion proteins was inhibited over a comparable concentration range while binding of the antagonist [3H]yohimbine was unaffected. These observations are consistent with the interpretation that the contact sites that are formed between individual receptors and G proteins differ. These differences suffice to allow for selective disruption by G protein inhibitors of different classes. Using NF326 we show that the bulk of the A1-adenosine receptors in human cerebrocortical membranes interacts with Galphao rather than Galphai.
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- Animals -
- Antineoplastic Agents - chemistry Antineoplastic Agents - metabolism Antineoplastic Agents - pharmacology
- Brain - metabolism
- COS Cells -
- Dose-Response Relationship, Drug -
- GTP-Binding Protein alpha Subunits, Gi-Go -
- GTP-Binding Proteins - metabolism
- Heterotrimeric GTP-Binding Proteins - metabolism
- Humans -
- Purinergic P1 Receptor Antagonists -
- Receptors, Purinergic P1 - metabolism
- Suramin - analogs & derivatives Suramin - metabolism Suramin - pharmacology
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- Find related publications in this database (Keywords)
- G proteins
- adenosine receptors
- alpha(2)-adrenoceptors
- suramin analogues
- fusion proteins
- human cerebral cortex