Lack of correlation between the amplitudes of TRP channel-mediated responses to weak and strong stimuli in intracellular Ca(2+) imaging experiments

Cell Calcium. 2013 Nov;54(5):362-74. doi: 10.1016/j.ceca.2013.08.005. Epub 2013 Sep 8.

Abstract

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.

Keywords: Calcium imaging; Fluorescence-activated cell sorting; PMCA; TRPA1; TRPM3; TRPM8; TRPV1; TRPV4.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acrolein / analogs & derivatives
  • Acrolein / pharmacology
  • Animals
  • CHO Cells
  • Calcium / metabolism*
  • Calcium Signaling / drug effects
  • Capsaicin / pharmacology
  • Cricetinae
  • Cricetulus
  • Flow Cytometry
  • Fura-2 / chemistry
  • Fura-2 / metabolism
  • HEK293 Cells
  • Humans
  • Leucine / analogs & derivatives
  • Leucine / pharmacology
  • Menthol / pharmacology
  • Pregnenolone / pharmacology
  • Sulfonamides / pharmacology
  • TRPV Cation Channels / agonists
  • TRPV Cation Channels / genetics
  • TRPV Cation Channels / metabolism*
  • Transfection

Substances

  • N-(1-((4-(2-(((2,4-dichlorophenyl)sulfonyl)amino)-3-hydroxypropanoyl)-1-piperazinyl)carbonyl)-3-methylbutyl)-1-benzothiophene-2-carboxamide
  • Sulfonamides
  • TRPV Cation Channels
  • pregnenolone sulfate
  • Menthol
  • Pregnenolone
  • Acrolein
  • Leucine
  • Capsaicin
  • cinnamaldehyde
  • Calcium
  • Fura-2