Study On Sensing Characteristics And Signal Encoding Logic Of Umami Receptors

Umami is one of the basic flavors?sour,bitter,salty,sweet,umami?,it represents the information of amino acids in food.The umami tastants are sensed by umami taste receptors,that mainly expressed in taste buds,and widely found in mammalian tissues and cells.Umami receptors include two types:metabotropic glutamate receptors?mGluR1 and mGluR4?and heterodimer T1R1/T1R,all of which belong to G-protein coupled receptor.At present,there are many studies on the signal transduction mechanism of umami,but due to the integrity and complexity of the taste signal,the signal difference of individual receptor in sensing the same substance has not been effectively studied.The quantitative analysis method proposed in this study about umami sensing and information coding ability could be help the future research and application of umami.The main research contents of this paper are as follows:?1?Firstly,taste bud sensors were constructed by using taste bud tissues from difference tongue regions of rabbit.Subsequently,detects the response current to MSG and IMP,Finally,receptor kinetics was used to analyze these current signals,the Shannon's theorem was used to quantitatively analyze the information coding amount of umami receptor to ligand signal.The taste bud sensor assembled by rabbit tongue was able to steadily respond to umami substances within 5 days,and different taste bud sensors have different intensity response currents for MSG and IMP.Every taste bud sensor could sense MSG and IMP based on enzyme-substrate kinetics.T1R1/T1R3 is the main receptor encoding umami signal,which is more expressed in the rostral tongue cells.Sensitivity to MSG,the rostral tongue is nearly 100 times stronger than caudal tongue.For MSG signals when the cell signal is maximized,only 5-7 receptors need to be activated.?2?Enzyme-linked immunosorbent assay?Elisa?and immunofluorescence?IF?were used to verify the quantification and localization of umami receptors on different parts of rabbit tongue.The results showed that the T1R1 receptor in the rostral tongue was higher than other parts,and the mGluR1 on caudal tongue was higher than other parts,especially in middle of the caudal tongue,and the largest amount;According to the analysis of fluorescence intensity,it could be concluded that three kinds of umami receptors exist in the front,middle and back of the tongue.In terms of distribution characteristics,it can be seen that the distribution of T1R1 and mGluR4 is relatively concentrated and the contour is clear,while the distribution of mGluR1 is more dispersed.The difference of the contours reflects the distribution of three umami receptors in tongue epithelial cells of different regions.?3?The aim of this chapter was to study the difference of sensing ability among three kinds of human umami receptors.The biosensor was constructed using human umami receptors,and its response current to monosodium glutamate?MSG?was determined by electrochemical workstation.The kinetic analysis showed that the allosteric constants of three kinds of umami receptors were:K_T1R1=7.183×10^-12 mol/L,K_mGluR1=1.659×10^-15 mol/L,K_mGluR4=7.61×10^-15 mol/L,respectively.The results indicate that there is a significant difference in the sensing of MSG among umami receptors,especially between T1R1 and mGluRs.The researching outcomes proved that among the three known human umami taste receptors,mGluR4 has the most robust sensitivity to MSG,followed by mGluR1,and T1R1 has the least sensitivity to MSG.T1R1/T1R3 is the main umami sensing receptor in human umami perception.