Lack of correlation between the amplitudes of TRP channel-mediated responses to weak and strong stimuli in intracellular Ca(2+) imaging experiments.
It is often observed in intracellular Ca(2+) imaging experiments that the amplitudes of the Ca(2+) signals elicited by newly characterized TRP agonists do not correlate with the amplitudes of the responses evoked subsequently by a specific potent agonist. We investigated this rather controversial phenomenon by first testing whether it is inherent to the comparison of the effects of weak and strong stimuli. Using five well-characterized TRP channel agonists in commonly used heterologous expression systems we found that the correlation between the amplitudes of the Ca(2+) signals triggered by two sequentially applied stimuli is only high when both stimuli are strong. Using mathematical simulations of intracellular Ca(2+) dynamics we illustrate that the innate heterogeneity in expression and functional properties of Ca(2+) extrusion (e.g. plasma membrane Ca(2+) ATPase) and influx (TRP channels) pathways across a cellular population is a sufficient condition for low correlation between the amplitude of Ca(2+) signals elicited by weak and strong stimuli. Taken together, our data demonstrate that this phenomenon is an expected outcome of intracellular Ca(2+) imaging experiments that cannot be taken as evidence for lack of specificity of low-efficacy stimuli, or as an indicator of the need of other cellular components for channel stimulation.
Laboratory for Ion Channel Research and TRP Research Platform Leuven (TRPLe), Department of Molecular Cell Biology, KU Leuven, Belgium.
Yeranddy A
YA
Alpizar
Alicia
A
Sanchez
Ahmed
A
Radwan
Islam
I
Radwan
Thomas
T
Voets
Karel
K
Talavera
D000171:Acrolein / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002211:Capsaicin / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D005434:Flow Cytometry; D016257:Fura-2 / Q000737:chemistry / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008610:Menthol / Q000494:pharmacology; D011284:Pregnenolone / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
C530602:N-(1-((4-(2-(((2,4-dichlorophenyl)sulfonyl)amino)-3-hydroxypropanoyl)-1-piperazinyl)carbonyl)-3-methylbutyl)-1-benzothiophene-2-carboxamide; D013449:Sulfonamides; D050916:TRPV Cation Channels; C018370:pregnenolone sulfate; D008610:Menthol; D011284:Pregnenolone; D000171:Acrolein; D007930:Leucine; D002211:Capsaicin; C012843:cinnamaldehyde; D002118:Calcium; D016257:Fura-2
Calcium imaging; Fluorescence-activated cell sorting; PMCA; TRPA1; TRPM3; TRPM8; TRPV1; TRPV4