Biology Reference
In-Depth Information
energy transfer (RET) or protein fragment complementation assays (PCA) are helping
us understand the stoichiometry of these complexes (
Ciruela, Vilardaga, & Fernandez-
Duenas, 2010; P´trin & H´bert, 2011; Vidi, Przybyla, Hu, &Watts, 2010
). The diver-
sity of responses induced by GPCRs is dependent not only on different types of ligands
but also on the arrangement of GPCR protomers within larger oligomeric complexes.
More importantly, the formation of oligomers can explain the signaling diversity and
the results obtained from ligand-binding studies on native receptors expressed in tissue.
Such heterooligomers, once fully characterized, may lead to the development of drugs
selective for a given pathway in a given cell type, with fewer undesirable effects. These
experiments can reveal other ligand-binding complexities in two ways: first, by exam-
ining additional ligands for the receptor partner and, second, by examining other dimer
partners in the same context. The use of siRNA in endogenous context could reveal
allostery with endogenous receptors.
SUMMARY
The measurement of ligand dissociation kinetics remains a unique way to determine
allosteric effects of small ligands, protein partners, or receptor dimerization, includ-
ing the symmetry of such interactions at the binding level. Since our capacity to use
other techniques (immunoprecipitation, fluorescence or bioluminescence resonance
energy transfer, etc.) to detect dimers is also limited to overexpression systems, using
radioligand binding kinetics may help detect such interactions between receptors in
endogenous systems using whole cells or purified membranes.
Acknowledgments
This study was supported by a Canadian Institutes of Health Research (CIHR) Team Grant in
GPCR Allosteric Regulation [CTiGAR, CTP 79848], in which both T.E.H. and S.A.L are both
coinvestigators, and CIHR grants to T.E.H. (CIHR; MOP-36379, MOP-123470) and S.A.L (CIHR,
MOP-74603, MOP-123470). T.E.H. is a Chercheur National of the “Fonds de la Recherche en
Sant
´
du Qu
´
bec” (FRSQ). S.A.L. is supported by a “Chercheur Senior” scholarship from FRSQ.
References
