Investigation of the role of the carboxyl terminal tails of the alpha and beta isoforms of the human thromboxane A2 receptor (TP) in mediating receptor : effector coupling
Files in This Item:
|Walsh et al TPa & TPb Gprotein Specificity BBA 2000.pdf||428.38 kB||Adobe PDF||Download|
|Title:||Investigation of the role of the carboxyl terminal tails of the alpha and beta isoforms of the human thromboxane A2 receptor (TP) in mediating receptor : effector coupling||Authors:||Walsh, Marie-Therese
Foley, John F.
Kinsella, B. Therese
|Permanent link:||http://hdl.handle.net/10197/3168||Date:||17-Apr-2000||Online since:||2011-09-22T16:10:32Z||Abstract:||We have investigated the functional coupling of alpha and beta isoforms of the human thromboxane A2 receptor (TP) to Galpha16 and Galpha12 members of the Gq and G12 families of heterotrimeric G proteins in human embryonic kidney (HEK) 293 cell lines HEK.alpha10 or HEK.beta3, stably over-expressing TPalpha and TPbeta, respectively. Moreover, using HEK.TP-328 cells which over-expresses a variant of TP truncated at the point of divergence of TPalpha and TPbeta we investigated the requirement of the C-tail per se in mediating G protein coupling and effector activation. Both TPalpha and TPbeta couple similarly to Galpha16 to affect increases in IP3 and mobilization of intracellular calcium ([Ca2+]i) in response to the TP agonist U46619. Whilst both TP isoforms mediated [Ca2+]i mobilization in cells co-transfected with Galpha12, neither receptor generated corresponding increases in IP3 indicating that the Galpha12 mediated increases in [Ca2+]i do not involve PLC activation. Verapamil, an inhibitor of voltage dependent Ca2+ channels reduced [Ca2+]i mobilization in TPalpha and TPbeta cells co-transfected with Galpha12 to approximately 40% of that mobilized in its absence whereas 3,4,5-trimethyloxybenzoic acid 8-(diethylamino)octyl ester (TMB-8), an antagonist of intracellular Ca2+ release, had no effect on [Ca2+]i mobilization by either receptor isoform co-transfected with Galpha12. Despite the lack of differential coupling specificity by TPalpha and TPbeta, TP-328 signaled more efficiently in the absence of a co-transfected G protein compared to the wild type receptors but, on the other hand, displayed an impaired ability to couple to co-transfected Galpha11, Galpha12 or Galpha16 subunits. In studies investigating the role of the C-tail in influencing coupling to the effector adenylyl cyclase, similar to TPalpha but not TPbeta, TP-328 coupled to GalphaS, leading to increased cAMP, rather than to Galphai. Whereas TP-328 signaled more efficiently in the absence of co-transfected G protein compared to the wild type TPalpha co-transfection of Galphas did not augment cAMP generation by TP-328. Hence, from these studies involving the wild type TPalpha, TPbeta and TP-328, we conclude that the C-tail sequences of TP are not a major determinant of G protein coupling specificity to Galpha11 and Galpha16 members of the Gq family or to Galpha12; it may play a role in determining GS versus Gi coupling and may act as a determinant of coupling efficiency.||Funding Details:||Health Research Board||Type of material:||Journal Article||Publisher:||Elsevier||Journal:||Biochimica et Biophysica Acta (BBA) - Molecular Cell Research||Volume:||1496||Issue:||2-3||Start page:||164||End page:||182||Copyright (published version):||2000 Elsevier Science B.V.||Keywords:||Thromboxane A2 receptor; G12; G16; Gs; Signalling||Subject LCSH:||Thromboxanes
|DOI:||10.1016/S0167-4889(00)00031-8||Other versions:||http://dx.doi.org/10.1016/S0167-4889(00)00031-8||Language:||en||Status of Item:||Peer reviewed|
|Appears in Collections:||Conway Institute Research Collection|
Biomolecular and Biomedical Science Research Collection
Show full item record
This item is available under the Attribution-NonCommercial-NoDerivs 3.0 Ireland. No item may be reproduced for commercial purposes. For other possible restrictions on use please refer to the publisher's URL where this is made available, or to notes contained in the item itself. Other terms may apply.