BIOL 4380 Lecture Notes - Lecture 11: G Protein–Coupled Receptor, Trpm5, Tas1R1
13 May 2018
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o Salty tastes are mediated by Na channels called amiloride channels, allows Na in
heeer there’s salt i the treh.
o Acidic and sour tastes, depend in the TRP channel.
o Sweet/umami depend on heterodimeric G protein coupled receptors. These receptors
form a large family called T1R1,2,3, depending on what the exact composition of the
heterodimer is, the receptor will be sensitive to either sweet or umami tastes. For sweet
we need T1R2 and 3. And for umami we need T1R1 and 3. The G protein cascade
downstream is the same for the 2 tastes and involved PLC: PLC beta 2 (activated by
alpha suuit of G protei) → produes IP seod esseger. IP atiates the TRPM5
which allows Ca in and depolarizes the taste cell.
o Bitter taste is sensed differently: we only need a sigle GPCR ooer → TR. for
certain reasons, bitter taste is understood much between than sweet and umami tastes.
The g protein is called gastducin, which activated PLC beta 2 and activated IP3 and then
TRPM5 and Ca entry.
o Be able to compare and contrast the 3 transduction pathways.
o Sit down and understand how the set of experiments were done: specificity in
peripheral taste coding supports the labeled line hypothesis: we have the wild type and
the TRPM5 +. We allow these mice to taste 3 different tastes. The behavioural response
e’re measuring, the mice are given 2 water bottles containing just water, or increased
oetratio of the tastes ad e oitor the ie’s approah to the ottle. Trp5
homozygous mouse has no response to increasing conc of sweetness. The same
behaviour is observed with umami and with bitter tastes.
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Document Summary
Salty tastes are mediated by na channels called amiloride channels, allows na in (cid:449)he(cid:374)e(cid:448)er there"s salt i(cid:374) the tre(cid:374)(cid:272)h, acidic and sour tastes, depend in the trp channel, sweet/umami depend on heterodimeric g protein coupled receptors. These receptors form a large family called t1r1,2,3, depending on what the exact composition of the heterodimer is, the receptor will be sensitive to either sweet or umami tastes. And for umami we need t1r1 and 3. The g protein cascade downstream is the same for the 2 tastes and involved plc: plc beta 2 (activated by alpha su(cid:271)u(cid:374)it of g protei(cid:374)) produ(cid:272)es ip(cid:1007) se(cid:272)o(cid:374)d (cid:373)esse(cid:374)ger. The g protein is called gastducin, which activated plc beta 2 and activated ip3 and then. We allow these mice to taste 3 different tastes. The behavioural response (cid:449)e"re measuring, the mice are given 2 water bottles containing just water, or increased (cid:272)o(cid:374)(cid:272)e(cid:374)tratio(cid:374) of the (cid:1007) tastes a(cid:374)d (cid:449)e (cid:373)o(cid:374)itor the (cid:373)i(cid:272)e"s approa(cid:272)h to the (cid:271)ottle.
