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  • Title: TRPC channel interactions with calmodulin and IP3 receptors.
    Author: Zhu MX, Tang J.
    Journal: Novartis Found Symp; 2004; 258():44-58; discussion 58-62, 98-102, 263-6. PubMed ID: 15104175.
    Abstract:
    Consistent with the conformational coupling mechanism, which suggests that store-operated channels are activated via physical interactions with intracellular calcium release channels, previous studies have demonstrated a functional coupling and a physical interaction between the transient receptor potential canonical type 3 (TRPC3) and inositol 1,4,5-trisphosphate receptor (IP3R). The IP3R-TRPC binding domains were determined using in vitro binding assays. This work aimed to study the effect of IP3R-TRPC interaction on TRPC function. Pull-down experiments were used to study the binding of TRPC to IP3R and to calmodulin. Patch clamp recordings in whole-cell and inside-out configurations were used to examine the effect of a TRPC-binding IP3R fragment, Ca2+ and calmodulin on TRPC activity. We found that IP3R and calmodulin compete for a common binding site at the TRPC C-terminus. TRPC channels are activated either by a peptide representing the TRPC-binding domain of IP3R or by inactivation of calmodulin from the excised membrane patches. TRPC3 activity is inhibited by Ca2+ and calmodulin. Therefore, we have identified a critical IP3R-TRPC interaction that is involved in the activation of TRPC-formed channels. We propose that IP3Rs activate TRPC channels by displacing inhibitory calmodulin from a common calmodulin-IP3R binding site located at the C-terminus of TRPC.
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