TRPC channel interactions with calmodulin and IP3 receptors
1Center for Molecular Neurobiology and Department of Neuroscience, The Ohio State University, 168 Rightmire Hall, 1060 Carmack Road, Columbus, Ohio 43210, USA.
Novartis Foundation Symposium
|April 24, 2004
Summary
Inositol 1,4,5-trisphosphate receptors (IP3Rs) activate TRPC3 channels by displacing calmodulin, a calcium-binding protein. This interaction at the TRPC C-terminus is crucial for store-operated calcium entry.
Area of Science:
- Cellular Biology
- Molecular Physiology
- Ion Channel Function
Background:
- Store-operated calcium entry is critical for cellular signaling.
- Conformational coupling suggests physical interactions between calcium release and influx channels.
- Previous studies show functional and physical coupling between TRPC3 and IP3R.
Purpose of the Study:
- To investigate the effect of IP3R-TRPC interaction on TRPC3 channel function.
- To identify the binding domains and mechanisms of IP3R-TRPC interaction.
- To elucidate the role of calmodulin in TRPC3 channel regulation.
Main Methods:
- In vitro binding assays to determine IP3R-TRPC binding domains.
- Pull-down experiments to assess TRPC3 binding to IP3R and calmodulin.
- Patch clamp electrophysiology (whole-cell and inside-out) to measure TRPC3 channel activity.
Main Results:
- IP3R and calmodulin compete for a common binding site on the TRPC3 C-terminus.
- TRPC3 channels are activated by an IP3R peptide or by removing calmodulin.
- TRPC3 channel activity is inhibited by Ca2+ and calmodulin.
Conclusions:
- A critical interaction between IP3R and TRPC3 is identified, mediating TRPC channel activation.
- IP3Rs activate TRPC channels by displacing inhibitory calmodulin from a shared binding site.
- This mechanism provides insight into the regulation of store-operated calcium entry.
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