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Direct interaction of adenosine with the TRPV1 channel protein.

ABSTRACT: Vanilloid receptor 1 (TRPV1), a nonspecific cation channel expressed primarily in small sensory neurons, mediates inflammatory thermal pain sensation. The function and expression of TRPV1 are enhanced during inflammation and certain neuropathies, leading to sustained hyperalgesia. Activation of TRPV1 in the spinal cord and periphery promotes release of adenosine, which produces analgesia by activating A(1) and A(2A) adenosine receptor (AR) on central and peripheral neurons. This study provides evidence of a direct interaction of AR analogs with TRPV1. Adenosine analogs inhibit TRPV1-mediated Ca(2+) entry in human embryonic kidney (HEK293) cells stably expressing TRPV1 (HEK/TRPV1) and DRG neurons. This inhibition was independent of A(2A)AR activation. Specific binding of [(3)H]resiniferatoxin (RTX) in plasma membrane preparations was inhibited by CGS21680, an A(2A)AR agonist. Similar degrees of inhibition were observed with both agonists and antagonists of ARs. Adenosine analogs inhibited [(3)H]RTX binding to affinity-purified TRPV1, indicative of a direct interaction of these ligands with the receptor. Furthermore, specific capsaicin-sensitive binding of [(3)H]CGS21680 was observed in Xenopus oocyte membranes expressing TRPV1. Capsaicin-induced inward currents in DRG neurons were inhibited by adenosine and agonist and antagonist of A(2A)AR at nanomolar concentrations. Increasing the concentrations of capsaicin reversed the inhibitory response to capsaicin, suggesting a competitive inhibition at TRPV1. Finally, exposure of HEK/TRPV1 cells to capsaicin induced an approximately 2.4-fold increase in proapoptotic cells that was abolished by adenosine analogs. Together, these data suggest that adenosine could serve as an endogenous inhibitor of TRPV1 activity by directly interacting with the receptor protein.

SUBMITTER: Puntambekar P

PROVIDER: S-EPMC6729738 | biostudies-literature | 2004 Apr

REPOSITORIES: biostudies-literature

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Direct interaction of adenosine with the TRPV1 channel protein.

Puntambekar Preeti P Van Buren Jeremy J Raisinghani Manish M Premkumar Louis S LS Ramkumar Vickram V

The Journal of neuroscience : the official journal of the Society for Neuroscience 20040401 14

Vanilloid receptor 1 (TRPV1), a nonspecific cation channel expressed primarily in small sensory neurons, mediates inflammatory thermal pain sensation. The function and expression of TRPV1 are enhanced during inflammation and certain neuropathies, leading to sustained hyperalgesia. Activation of TRPV1 in the spinal cord and periphery promotes release of adenosine, which produces analgesia by activating A(1) and A(2A) adenosine receptor (AR) on central and peripheral neurons. This study provides e ...[more]

PMID: 15071115

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Project description:Human ether-á-go-go (eag)-related gene (hERG) potassium channel kinetics are characterized by rapid inactivation upon depolarization, along with rapid recovery from inactivation and very slow closing (deactivation) upon repolarization. These factors combine to create a resurgent hERG current, where the current amplitude is paradoxically larger with repolarization than with depolarization. Previous data showed that the hERG N-terminal eag domain regulated deactivation kinetics by making a direct interaction with the C-terminal region of the channel. A primary mechanism for fast inactivation depends on residues in the channel pore; however, inactivation was also shown to be slower after deletion of a large N-terminal region. The mechanism for N-terminal region regulation of inactivation is unclear. Here, we investigated the contributions of the large N-terminal domains (amino acids 1-354), including the eag domain (amino acids 1-135), to hERG channel inactivation kinetics and steady-state inactivation properties. We found that N-deleted channels lacking just the eag domain (Δ2-135) or both the eag domain and the adjacent proximal domain (Δ2-354) had less rectifying current-voltage (I-V) relationships, slower inactivation, faster recovery from inactivation, and lessened steady-state inactivation. We coexpressed genetically encoded N-terminal fragments for the eag domain (N1-135) or the eag domain plus the proximal domain (N1-354) with N-deleted hERG Δ2-135 or hERG Δ2-354 channels and found that the resulting channels had more rectifying I-V relationships, faster inactivation, slower recovery from inactivation, and increased steady-state inactivation, similar to those properties measured for wild-type (WT) hERG. We also found that the eag domain-containing fragments regulated the time to peak and the voltage at the peak of a resurgent current elicited with a ramp voltage protocol. The eag domain-containing fragments effectively converted N-deleted channels into WT-like channels. Neither the addition of the proximal domain to the eag domain in N1-354 fragments nor the presence of the proximal domain in hERG Δ2-135 channels measurably affected inactivation properties; in contrast, the proximal region regulated steady-state activation in hERG Δ2-135 channels. The results show that N-terminal region-dependent regulation of channel inactivation and resurgent current properties are caused by a direct interaction of the eag domain with the rest of the hERG channel.

Dataset Information

Direct interaction of adenosine with the TRPV1 channel protein.

Publications

Direct interaction of adenosine with the TRPV1 channel protein.

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