Human 5-HT3A -- Arg 440

Species Original Mutated to Mutation
Human Arg 440 Ala

R440A

Rat Equivalent Arg 439    
Mouse Equivalent Arg 446

 

Leu

Ala

Asp

Glu

Gly

His

Lys

Trp

Asn

R427L

R427A

R427D

R427E

R427G

R427H

R427K

R427W

R427N

 

h#hArg440Ala

This mutation caused a 3-fold increase in single-channel conductance. When it was combined with R436D, the double mutation produced conductance that was greater than the sum of the individual mutations. When it was combined with R432Q, there was no such synergy. In a triple mutation of R432Q, R436D, and R440A, the single-channel conductance increased substantially.

Kelley SP, Dunlop JI, Kirkness EF, Lambert JJ, Peters JA (2003) A Cytoplasmic Region Determines Single-Channel Conductance in 5-HT3 Receptors. Nature 424(6946):321-324

back to top
back to 5-HT3A

 

In this study the cytoplasmic membrane-associated (MA) helix arginine residues 432 (-4'), 436 (0'), and 440 (4') of a homomeric 5HT3AR were replaced with equivalent residues found in 5HT3B to determine if these mutations had any effect on single channel conductance (γ). The techniques of whole-cell and outside-out patch recording were used to measure γ indirectly (by variance analysis) and directly (from single channel amplitudes), respectively. The study concluded that the MA 0' position had the greatest effect on γ.

The R440A mutation caused an ~5-fold increase in γ. The R432Q, R440A two-point mutation caused an ~7-fold increase in γ. The R436D, R440A two-point mutation caused an ~26-fold increase in γ. The R432Q, R436D, R440A three-point mutation caused an ~38-fold increase in γ. The R432Q, R436E, R440A three-point mutation caused an ~36-fold increase in γ. The R432Q, R436Q, R440A three-point mutation caused an ~24-fold increase in γ. The R432Q, R436F, R440A three-point mutation caused an ~2-fold increase in γ.

Hales TG, Dunlop JI, Deeb TZ, Carland JE, Kelley SP, Lambert JJ, Peters JA (2006) Common Determinants of Single Channel Conductance within the Large Cytoplasmic Loop of 5-Hydroxytryptamine Type 3 and α4β2 Nicotinic Acetylcholine Receptors. The Journal of Biological Chemistry 281(12):8062-71

back to top
back to 5-HT3A

mArg446Leu

This study demonstrated that the physicochemical properties of residue 446 (listed as R427 in this paper) affects the rate of desensitization of the long isoform of the mouse 5-HT3A receptor. By sequential deletion of pieces of the large cytoplasmic domain, the researchers narrowed down the effects on desensitization to the MA-helix. They subsequently determined that R446 was the key effector. Furthermore, they found that the more hydrophobic the sidechain of the substituted residue, the slower the rate of desensitization. Charged susbstitutions such as glutamate and aspartate had little effect despite a reversal of charge relative to the wild type arginine residue at this position. The researchers analyzed several substituted residues and found that subsitituion by leucine had the greatest effect on desensitization. This paper supports a role for this region in determining receptor desensitization, a process that had largely been attributed to residues in the extracellular and transmembrane regions. The mechanism by which this residue affects desensitization remains undetermined.

Hu XQ, Sun H, Peoples RW, Hong R, Zhang L. (2006) An interaction involving an arginine residue in the cytoplasmic domain of the 5-HT3A receptor contributes to receptor desensitization mechanism. The Journal of Biological Chemistry 281(31):21781-8

back to top
go back to 5-HT3A

Previous Next