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Bitter Taste Receptor T2R4 Mediated Inactivation of Rac1 GTPase in Response to Quinine
Author(s) -
Sidhu Crystal,
Jaggupilli Appalaraju,
Chelikani Prashen,
Bhullar Rajinder P
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.866.2
Subject(s) - rac1 , g protein coupled receptor , microbiology and biotechnology , guanine nucleotide exchange factor , gtpase , chemistry , biology , biochemistry , lamellipodium , signal transduction , cytoskeleton , cell
Rac1 is a member of the Rho family of low molecular mass GTP binding proteins (GTPases). It regulates the dynamics of actin cytoskeleton by causing membrane ruffling, chemotaxis, and lamellipodia formation. Rac1 has been recently implicated in cancer metastasis and progression. As is the case with other GTPases, Rac1 cycles between the active GTP‐bound form and the inactive GDP‐bound form. This step is facilitated by a variety of Guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). T2R4 is a bitter taste receptor that belongs to the GPCR (G protein‐coupled receptor) family of membrane proteins. In addition to mediating bitter taste sensations from the tongue, T2R4 and other T2Rs have been recently found in tissues other than the oral cavity e.g. nasal epithelium, airways, brain, gastrointestinal tract and male reproductive system suggesting a much broader physiological function for these receptors. T2Rs have been implicated in bronchodilation and in vasoconstriction. Quinine is an antimalarial drug and is one of the most bitter tasting compounds known. It is a natural alkaloid with a quinoline ring and a bicyclic quinuclidine. Quinine is a known agonist for T2Rs whereas BCML (Nα,Nα‐Bis(carboxymethyl)‐L‐lysine) acts as an inverse agonist. Since Rac1 is activated via various receptors like tyrosine kinase (RTKs), integrins and GPCRs; we have investigated the potential role of T2R4 in regulating Rac1 activity. In this study, HEK293T cells stably expressing T2R4/Gα 16/44 were transiently transfected with HA‐Rac1 followed by treatment with Quinine or Quinine plus BCML for 15 min. After incubation, active Rac1 was pulled‐down from cell lysate using GST‐PAK1 and anti‐Rac1 monoclonal antibody was used in Western blots to quantify amount of active Rac1. The results demonstrated that Quinine treatment resulted in significant (p<0.001) reduction in the amount of active Rac1 whereas in the presence of BCML, Quinine failed to cause any significant change in the amount of active Rac1 when compared to untreated cells. This study is the first to show inhibitory downstream action of a T2R agonist on Rac1 function and further investigation will help in better understanding the extra‐oral physiological roles of T2Rs. Support or Funding Information This work is supported by a grant from Research Manitoba and the College of Dentistry.