Open AccessSearch for adenosine A 2A spare receptors on peripheral human lymphocytes
Author(s) -
Jacquin Laurent,
Franceschi Frédéric,
By Youlet,
Durand-Gorde Josée-Martine,
Condo Jocelyne,
Deharo Jean-Claude,
Michelet Pierre,
Fenouillet Emmanuel,
Guieu Régis,
Ruf Jean
Publication year - 2013
Publication title -
febs open bio
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.718
H-Index - 31
ISSN - 2211-5463
DOI - 10.1016/j.fob.2012.11.004
Subject(s) - spare part , adenosine , receptor , peripheral , chemistry , computational biology , microbiology and biotechnology , biology , biochemistry , medicine , business , marketing
Some ligand–receptor couples involve spare receptors, which are apparent when a maximal response is achieved with only a small fraction of the receptor population occupied. This situation favours cross‐reactions with low‐affinity ligands, which may be detrimental for cell signaling. In the case of the adenosine A 2A receptors (A 2A R), which have an immunosuppressive effect on lymphocytes through cAMP production, the presence of spare A 2A R remains to be established. We examined the situation using patients over‐expressing lymphocyte A 2A R and an agonist‐like mAb to A 2A R. We found that maximal mAb binding and functional response varied among the patients whereas the dissociation constant and half‐maximal effective concentration had similar mean values (0.19 and 0.18 μM, respectively). Lymphocyte A 2A R expression was correlated to plasma adenosine level and A 2A R occupation but not to A 2A R response. These results are consistent with a lack of a reserve of functional A 2A R on human lymphocytes as a general rule and suggest that the amount and functional state of the expressed A 2A R determine the maximal level of the lymphocyte response to adenosine.