Alpha-Gustducin is a G protein alpha subunit that plays a key role in signal transduction of compounds humans consider either sweet or bitter. The gustducin heterotrimer is thought to transduce responses from a family of bitter responsive receptors to activation of phosphodiesterase and phospholipase Cbeta2. Alpha-Gustducin knockout mice have reduced behavioral and electrophysiological responses to certain bitter and sweet compounds. Alpha-Gustducin is highly expressed in taste receptor cells, but is also expressed in the brush cells of the stomach, intestine and pancreatic ducts. Alpha-Gustducin expressing cells of the digestive tract are suspected to be the chemosensory cells of the gut that may be involved in regulating resorption, secretion of digestive hormones and intestinal motility. To study alpha-gustducin expressing cells we have produced transgenic mice expressing green fluorescent protein (GFP) under the control of 7.7 kb of the 5' flanking region of the alpha-gustducin gene. GFP was expressed in a subset of taste receptor cells, but co-localization of alpha-gustducin and GFP was found in 80-95% of the cells, depending on the particular transgenic line. Moreover GFP was not expressed in the alpha-gustducin positive cells of the gut, and it was ectopically expressed in alpha-gustducin negative cells of the retina. To address these shortfalls of the transgenic mice, we propose to produce knock-in mice in which red fluorescent protein (RFP) and a truncated human CD4 are introduced into the alpha-gustducin locus such that they are faithfully expressed under the control of the cis-acting elements that control endogenous alpha-gustducin expression RFP will be used as a marker of alpha-gustducin-expressing cells. The truncated CD4 will be used as a surface marker to purify these cells after labeling them with an anti-CD4 antibody linked to a magnetic bead, using magnetic cell sorting. The knock-in mice and the purified cells will provide important reagents with which to determine the genes that are co-expressed with alpha-gustducin, to produce cDNA libraries from alpha-gustducin expressing taste and gut cells, and to study the response of the putative chemoreceptor cells of the gut to various compounds, using calcium imaging and electrophysiology.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Small Research Grants (R03)
Project #
1R03DC004766-01
Application #
6310868
Study Section
Special Emphasis Panel (ZDC1-SRB-O (23))
Program Officer
Davis, Barry
Project Start
2001-01-01
Project End
2003-12-31
Budget Start
2001-01-01
Budget End
2001-12-31
Support Year
1
Fiscal Year
2001
Total Cost
$84,750
Indirect Cost
Name
Mount Sinai School of Medicine
Department
Physiology
Type
Schools of Medicine
DUNS #
114400633
City
New York
State
NY
Country
United States
Zip Code
10029
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He, Wei; Yasumatsu, Keiko; Varadarajan, Vijaya et al. (2004) Umami taste responses are mediated by alpha-transducin and alpha-gustducin. J Neurosci 24:7674-80
He, Wei; Danilova, Vicktoria; Zou, Shiying et al. (2002) Partial rescue of taste responses of alpha-gustducin null mice by transgenic expression of alpha-transducin. Chem Senses 27:719-27
Ruiz-Avila, L; Wong, G T; Damak, S et al. (2001) Dominant loss of responsiveness to sweet and bitter compounds caused by a single mutation in alpha -gustducin. Proc Natl Acad Sci U S A 98:8868-73