J Biol Chem. 2004 Apr 2;279(14):13696-704. Epub 2004 Jan 21.
Ca(2+) signaling by TRPC3 involves Na(+) entry and local coupling to the Na(+)/Ca(2+) exchanger.
Rosker, C., Graziani, A., Lukas, M., Eder, P., Zhu, M. X., Romanin, C., Groschner, K.,
["Department of Pharmacology and Toxicology, Karl-Franzens-University Graz, A-8010 Graz, Austria."]
["Department of Pharmacology and Toxicology, Karl-Franzens-University Graz, A-8010 Graz, Austria."]
TRPC3 has been suggested as a key component of phospholipase C-dependent Ca(2+) signaling. Here we investigated the role of TRPC3-mediated Na(+) entry as a determinant of plasmalemmal Na(+)/Ca(2+) exchange. Ca(2+) signals generated by TRPC3 overexpression in HEK293 cells were found to be dependent on extracellular Na(+), in that carbachol-stimulated Ca(2+) entry into TRPC3 expressing cells was significantly suppressed when extracellular Na(+) was reduced to 5 mm. Moreover, KB-R9743 (5 microm) an inhibitor of the Na(+)/Ca(2+) exchanger (NCX) strongly suppressed TRPC3-mediated Ca(2+) entry but not TRPC3-mediated Na(+) currents. NCX1 immunoreactivity was detectable in HEK293 as well as in TRPC3-overexpressing HEK293 cells, and reduction of extracellular Na(+) after Na(+) loading with monensin resulted in significant rises in intracellular free Ca(2+) (Ca(2+)(i)) of HEK293 cells. Similar rises in Ca(2+)(i) were recorded in TRPC3-overexpressing cells upon the reduction of extracellular Na(+) subsequent to stimulation with carbachol. These increases in Ca(2+)(i) were associated with outward membrane currents at positive potentials and inhibited by KB-R7943 (5 microm), chelation of extracellular Ca(2+), or dominant negative suppression of TRPC3 channel function. This suggests that Ca(2+) entry into TRPC3-expressing cells involves reversed mode Na(+)/Ca(2+) exchange. Cell fractionation experiments demonstrated co-localization of TRPC3 and NCX1 in low density membrane fractions, and co-immunoprecipitation experiments provided evidence for association of TRPC3 and NCX1. Glutathione S-transferase pull-down experiments revealed that NCX1 interacts with the cytosolic C terminus of TRPC3. We suggest functional and physical interaction of nonselective TRPC cation channels with NCX proteins as a novel principle of TRPC-mediated Ca(2+) signaling.
PMID: 14736881
 Screening
Validation: In vitro validation
Validation: In vivo validation
Characterization
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Screening
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| Experimental screening | Non-experimental screening | Reference | ||||||||
| TRP channel construct | Interactor source | |||||||||
| TRP channel | Interactor | Method | Species | Region | Species | Organ/tissue | Sample type | |||
| TRPC3 |
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NCX1 | Inference | Prediction | 14736881 | |||||
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
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Screening
Validation: In vitro validation
Validation: In vivo validation
Characterization
Functional consequence
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| Validation: In vitro validation
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| Assay with recombinant proteins | Reference | |||||||||
| TRP channel construct | Interactor construct | |||||||||
| TRP channel | Interactor | Method | Species | Region | Expression system | Species | Region | Expression system | ||
| TRPC3 |
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NCX1 | Fusion protein-pull down assay | Human | 742-848 | E. coli | Not used | HEK293 lysates | 14736881 | |
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
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Screening
Validation: In vitro validation
Validation: In vivo validation
Characterization
Functional consequence
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top
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| Validation: In vivo validation
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| Assay with endogenous proteins | Assay with overexpressed proteins | Reference | ||||||||
| Cell or tissue | Cell or tissue | TRP channel construct | Interactor construct | |||||||
| TRP channel | Interactor | Method | Species | Region | Species | Region | ||||
| TRPC3 |
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NCX1 | Co-immunoprecipitation | HEK293 | Human | Full-length | Not used | 14736881 | ||
(:
click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
:
click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)