Biochemistry. 2003 Jun 24;42(24):7618-25.
Troponin I binds polycystin-L and inhibits its calcium-induced channel activation.
Li, Q., Liu, Y., Shen, P. Y., Dai, X. Q., Wang, S., Smillie, L. B., Sandford, R., Chen, X. Z.,
["Membrane Protein Research Group, Department of Physiology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada."]
["Membrane Protein Research Group, Department of Physiology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada."]
Polycystin-L (PCL) is an isoform of polycystin-2, the product of the second gene associated with autosomal dominant polycystic kidney disease, and functions as a Ca(2+)-regulated nonselective cation channel. We recently demonstrated that polycystin-2 interacts with troponin I, an important regulatory component of the actin microfilament complex in striated muscle cells and an angiogenesis inhibitor. In this study, using the two-microelectrode voltage-clamp technique and Xenopus oocyte expression system, we showed that the calcium-induced PCL channel activation is substantially inhibited by the skeletal and cardiac troponin I (60% and 31% reduction, respectively). Reciprocal co-immunoprecipitation experiments demonstrated that PCL physically associates with the skeletal and cardiac troponin I isoforms in overexpressed Xenopus oocytes and mouse fibroblast NIH 3T3 cells. Furthermore, both native PCL and cardiac troponin I were present in human heart tissues where they indeed associate with each other. GST pull-down and microtiter binding assays showed that the C-terminus of PCL interacts with the troponin I proteins. The yeast two-hybrid assay further verified this interaction and defined the corresponding interacting domains of the PCL C-terminus and troponin I. Taken together, this study suggests that troponin I acts as a regulatory subunit of the PCL channel complex and provides the first direct evidence that PCL is associated with the actin cytoskeleton through troponin I.
PMID: 12809519

![]() ![]() ![]() ![]() ![]() |
![]() |
Screening
![]() |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Experimental screening | Non-experimental screening | Reference | ||||||||
TRP channel construct | Interactor source | |||||||||
TRP channel | Interactor | Method | Species | Region | Species | Organ/tissue | Sample type | |||
TRPP2 |
![]() |
Troponin I 1 | Inference | Prediction | 12809519 | |||||
TRPP2 |
![]() |
Troponin I 2 | Inference | Prediction | 12809519 | |||||
TRPP2 |
![]() |
Troponin I 3 | Inference | Prediction | 12809519 |
(
:
click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)

![]() ![]() ![]() ![]() ![]() |
![]() |
Validation: In vitro validation
![]() |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Assay with recombinant proteins | Reference | |||||||||
TRP channel construct | Interactor construct | |||||||||
TRP channel | Interactor | Method | Species | Region | Expression system | Species | Region | Expression system | ||
TRPP2 |
![]() |
Troponin I 1 | Fusion protein-pull down assay | Human | 562-805 | E. coli | Human | Not specified | Not specified | 12809519 |
TRPP2 |
![]() |
Troponin I 2 | Fusion protein-pull down assay | Human | 562-805 | E. coli | Human | Not specified | Not specified | 12809519 |
TRPP2 |
![]() |
Troponin I 3 | Fusion protein-pull down assay | Human | 562-805 | E. coli | Human | Not specified | Not specified | 12809519 |
(
:
click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)

![]() ![]() ![]() ![]() ![]() |
![]() |
Validation: In vivo validation
![]() |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|
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 | ||||
TRPP2 |
![]() |
Troponin I 1 | Co-immunoprecipitation | NIH-3T3 | Human | Full-length | Human | Full-length | 12809519 | |
TRPP2 |
![]() |
Troponin I 1 | Co-immunoprecipitation | Xenopus oocyte | Human | Full-length | Human | Full-length | 12809519 | |
TRPP2 |
![]() |
Troponin I 2 | Co-immunoprecipitation | NIH-3T3 | Human | Full-length | Human | Full-length | 12809519 | |
TRPP2 |
![]() |
Troponin I 2 | Co-immunoprecipitation | Xenopus oocyte | Human | Full-length | Human | Full-length | 12809519 | |
TRPP2 |
![]() |
Troponin I 3 | Co-immunoprecipitation | NIH-3T3 | Human | Full-length | Human | Full-length | 12809519 | |
TRPP2 |
![]() |
Troponin I 3 | Co-immunoprecipitation | Xenopus oocyte | Human | Full-length | Human | Full-length | 12809519 | |
TRPP2 |
![]() |
Troponin I 3 | Co-immunoprecipitation | Human adult cardiac tissue | 12809519 |
(
:
click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)

![]() ![]() ![]() ![]() ![]() |
![]() |
Characterization
![]() |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Binding region mapping | Stoichiometry | Affinity (Kd) | Reference | |||||||
TRP channel | Interactor | |||||||||
TRP channel | Interactor | Method | Species | Region | Species | Region | ||||
TRPP2 |
![]() |
Troponin I 3 | Yeast two-hybrid | Human | 630-705 | Human | Not determined | 12809519 | ||
TRPP2 |
![]() |
Troponin I 3 | Yeast two-hybrid | Human | 562-805 | Human | 1-170 | 12809519 | ||
TRPP2 |
![]() |
Troponin I 3 | Yeast two-hybrid | Human | 562-805 | Human | 106-158 | 12809519 |
(
:
click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)

![]() ![]() ![]() ![]() ![]() |
![]() |
Functional consequence
![]() |
||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
TRP channel | Interactor | Method | Post-translational modification | Subcellular trafficking | Activity | Reference | ||||||
TRPP2 |
![]() |
Troponin I 1 | Calcium measurement | Inhibition | 12809519 | |||||||
TRPP2 |
![]() |
Troponin I 1 | Patch clamp | Inhibition | 12809519 | |||||||
TRPP2 |
![]() |
Troponin I 3 | Calcium measurement | Inhibition | 12809519 |
(
:
click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
