Differential contribution of SNARE‐dependent exocytosis to inflammatory potentiation of TRPV1 in nociceptors

Abstract

Potentiation of the pain-integrator ion channel transient receptor potential vanilloid type 1 (TRPV1) underlies thermal hyperalgesia mediated by a variety of proinflammatory factors. Two complementary mechanisms of TRPV1 inflammatory sensitization have been proposed, namely a decrease of its activation threshold and an increment of its surface expression in nociceptors. Here we investigated the involvement of regulated exocytosis to the inflammatory sensitization of TRPV1 in rat neonatal dorsal root ganglion neurons by proalgesic agents. The contribution of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-dependent exocytosis was evaluated using a small peptide patterned after the synaptosomal-associated protein of 25 kDa (SNAP-25) protein that acts as a specific and potent inhibitor of neuronal exocytosis. We found that TRPV1 sensitization mediated by nerve growth factor, ATP, and IGF-I was accompanied by a higher channel expression in the neuronal plasma membrane, which was prevented by blockade of regulated exocytosis. In contrast, TRPV1 sensitization caused by bradykinin, IL-1beta, and artemin was insensitive to inhibition of SNARE-dependent vesicular fusion and was not due to an increase in TRPV1 surface expression. Therefore, it appears that some, but not all, proinflammatory agents sensitize rat nociceptors by promoting the recruitment of TRPV1 channels to the neuronal surface. These findings support the tenet that SNARE complex-mediated exocytosis of TRPV1 may be a valid therapeutic target to treat inflammatory pain.

Agonist- and Ca2+-dependent Desensitization of TRPV1 Channel Targets the Receptor to Lysosomes for Degradation

“…However, the contribution of TRPV1 mobilization from the plasma membrane to intracellular reservoirs as a mechanism to attenuate nociceptor overactivity has not yet been evaluated in detail. We and others have shown that TRPV1 sensitization is achieved at least in part by rapid recruitment of a subcellular population of vesicular TRPV1 that becomes translocated to the plasma membrane by regulated exocytosis under inflammatory conditions (21,23,36). Therefore, the opposite mechanism, i.e.…”

“…23. HEK293 cells were cultured as described (24) and used 48 h after transfection with TurboFect (Fermentas Life Sciences) following the manufacturer's instructions.…”

Sensory and Signaling Mechanisms of Bradykinin, Eicosanoids, Platelet-Activating Factor, and Nitric Oxide in Peripheral Nociceptors

“…Bradykinin was shown to cause translocation of PKC in cultured DRG neurons (746). Considerable evidence has been provided for the involvement of PKC in the various excitatory (nocifensive or spikegenerating) and sensitizing effects of bradykinin studying transfected cells, cultured sensory neurons (85,94,95,120,296,411,435,585,586,685,745,764; see details in sect. IIC3), nerve fiber discharge (252,253,497), nocifensive behavior (186), and neuropeptide release (200).…”

Cyclin-Dependent Kinase 5 Controls TRPV1 Membrane Trafficking and the Heat Sensitivity of Nociceptors through KIF13B

“…As a transmembrane receptor, the number of functional TRPV1s at the plasma membrane must be a critical determinant of channel function, and potentiating channel function by increasing its levels at the cell surface is a potential mechanism underlying proinflammatory mediator-induced heat hyperalgesia (Ji et al, 2002;Van Buren et al, 2005;Zhang et al, 2005;Stein et al, 2006;Camprubí-Robles et al, 2009). In general, the number of receptors at the surface can be regulated by the membrane trafficking and insertion of receptors.…”

“…In general, the number of receptors at the surface can be regulated by the membrane trafficking and insertion of receptors. To date, studies have shown that PKC activation-sensitized SNARE-dependent exocytosis and Src-dependent phosphorylation of TRPV1 are involved in inflammatory stimuli-induced rapid membrane insertion of TRPV1s from a ready-to-go vesicular pool (Morenilla-Palao et al, 2004;Zhang et al, 2005;Camprubí-Robles et al, 2009), but the mechanisms that regulate transport of TRPV1s from the Golgi apparatus to the plasma membrane of sensory neurons is essentially unclear. Kinesin superfamily motor proteins are responsible for the intracellular anterograde transport of most cargos, including transmembrane receptors (Hirokawa et al, 2009).…”