Activation of Inositol 1,4,5-Trisphosphate Receptor Is Essential for the Opening of Mouse TRP5 Channels

Abstract

We studied the opening mechanism of Ca(2+)-permeable channels formed with mouse transient receptor potential type 5 (mTRP5) using Xenopus oocytes. After stimulation of coexpressed muscarinic M(1) receptors with acetylcholine (ACh) in a Ca(2+)-free solution, switching to 2 mM Ca(2+)-containing solution evoked a large Cl(-) current, which reflects the opening of endogenous Ca(2+)-dependent Cl(-) channels following Ca(2+) entry through the expressed channels. The ACh-evoked response was not affected by a depletion of Ca(2+) store with thapsigargin but was inhibited by preinjection of antisense oligodeoxynucleotides (ODNs) to G(q), G(11), or both. The mTRP5 channel response was also induced by a direct activation of G proteins with injection of guanosine 5'-3-O-(thio)triphosphate (GTP gamma S). The ACh- and GTP gamma S-evoked responses were inhibited by either pretreatment with a phospholipase C inhibitor, U73122, or an inositol-1,4,5-trisphosphate (IP(3)) receptor inhibitor, xestospongin C (XeC). An activation of IP(3) receptors with injection of adenophostin A (AdA) evoked the mTRP5 channel response in a dose-dependent manner. The AdA-evoked response was not suppressed by preinjection of antisense ODNs to G(q/11) or U73122 but was suppressed by either preinjection of XeC or a peptide mimicking the IP(3) binding domain of Xenopus IP(3) receptor. These findings suggest that the activation of IP(3) receptor is essential for the opening of mTRP5 channels, and that neither G proteins, phosphoinositide metabolism, nor depletion of the Ca(2+) store directly modifies the IP(3) receptor-linked opening of mTRP5 channels.

Vomeronasal sensory neurons fromSternotherus odoratus(stinkpot/musk turtle) respond to chemosignalsviathe phospholipase C system

“…We designed a peptide (see Materials and methods) against this sequence to interrupt the binding of IP 3 R3 to TRPC2 and analyzed its effect on the chemosignal response over time in musk turtle VSNs, and found that 10·mol·1 -1 peptide nearly abolished the chemosignalactivated current by 10·min. The use of a peptide to disrupt the interaction between the IP 3 R and a TRPC channel has been shown previously; in Xenopus oocytes, suppression of the mTRPC5 current was seen with preinjection of a peptide mimicking the IP 3 binding domain of the IP 3 R (Kanki et al, 2001). These results indicate that there is a functional role for the IP 3 R in the VNO of the musk turtle.…”

Regulation of Canonical Transient Receptor Potential (TRPC) Channel Function by Diacylglycerol and Protein Kinase C

“…Indeed, recent evidence indicates that there is an important functional requirement of InsP 3 Rs for the TRPC5 channel (32). Using DT40-InsP 3 R Ϫ/Ϫ cells transiently cotransfected with TRPC5 and eYFP (Fig.…”

Critical roles of Gi/oproteins and phospholipase C-δ1 in the activation of receptor-operated TRPC4 channels

“…Therefore, in addition to supporting TRPC4 function, PIP 2 also exerts a tonic inhibition on the channel. (21,(24)(25)(26)(27)(28)32). To determine if IP 3 Rs are involved in TRPC4 activation, we applied the IP 3 R inhibitor heparin (3 mg/mL) by intracellular dialysis and found that most cells failed to respond to DAMGO and subsequent application of CCh (Fig.…”