AMP is an adenosine A1 receptor agonist.
Numerous receptors for ATP, ADP, and adenosine exist; however, it is currently unknown whether a receptor for the related nucleotide adenosine 5'-monophosphate (AMP) exists. Using a novel cell-based assay to visualize adenosine receptor activation in real time, we found that AMP and a non-hydrolyzable AMP analog (deoxyadenosine 5'-monophosphonate, ACP) directly activated the adenosine A(1) receptor (A(1)R). In contrast, AMP only activated the adenosine A(2B) receptor (A(2B)R) after hydrolysis to adenosine by ecto-5'-nucleotidase (NT5E, CD73) or prostatic acid phosphatase (PAP, ACPP). Adenosine and AMP were equipotent human A(1)R agonists in our real-time assay and in a cAMP accumulation assay. ACP also depressed cAMP levels in mouse cortical neurons through activation of endogenous A(1)R. Non-selective purinergic receptor antagonists (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid and suramin) did not block adenosine- or AMP-evoked activation. Moreover, mutation of His-251 in the human A(1)R ligand binding pocket reduced AMP potency without affecting adenosine potency. In contrast, mutation of a different binding pocket residue (His-278) eliminated responses to AMP and to adenosine. Taken together, our study indicates that the physiologically relevant nucleotide AMP is a full agonist of A(1)R. In addition, our study suggests that some of the physiological effects of AMP may be direct, and not indirect through ectonucleotidases that hydrolyze this nucleotide to adenosine.
Department of Cell and Molecular Physiology, University of North Carolina Neuroscience Center, Chapel Hill, North Carolina 27599, USA.
Joseph E
JE
Rittiner
Ilia
I
Korboukh
Emily A
EA
Hull-Ryde
Jian
J
Jin
William P
WP
Janzen
Stephen V
SV
Frye
Mark J
MJ
Zylka
D015720:5'-Nucleotidase / Q000378:metabolism; D000241:Adenosine / Q000378:metabolism; D058907:Adenosine A1 Receptor Agonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000249:Adenosine Monophosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology; D005576:Colforsin / Q000494:pharmacology; D057809:HEK293 Cells; D006639:Histidine; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D008024:Ligands; D051379:Mice; D057054:Molecular Imaging; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D043682:Receptor, Adenosine A1 / Q000737:chemistry / Q000378:metabolism*; D043704:Receptor, Adenosine A2B / Q000378:metabolism; D058470:Receptors, Purinergic P2Y / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000819:agonists / Q000737:chemistry / Q000378:metabolism; D059010:Single-Cell Analysis
D058907:Adenosine A1 Receptor Agonists; D008024:Ligands; D043682:Receptor, Adenosine A1; D043704:Receptor, Adenosine A2B; D058470:Receptors, Purinergic P2Y; D011993:Recombinant Fusion Proteins; D005576:Colforsin; D000249:Adenosine Monophosphate; D006639:Histidine; D015720:5'-Nucleotidase; D000241:Adenosine