Regulation Of Kcnq2/3 Channels By The Transcriptional Repressor REST In Nociception

Abstract

Understanding how excitability of sensory neurons is regulated is an important goal since this excitability underlies pain transmission and unfortunately almost everyone will suffer from inflammatory pain at some point in their life. Recent studies have identified expression of M-type K+ channels (encoded by KCNQ genes) in damage-sensing (nociceptive) sensory neurons, where they are thought to control excitability. Accordingly, receptor-induced inhibition of M-current in these neurons has been shown to contribute to peripheral sensitisation and inflammatory pain. Here we describe a new mechanism for downregulation of KCNQ channel expression in nociceptors. We identified binding sites for the transcriptional repressor REST within both the KCNQ2 and KCNQ3 genes. Dorsal root ganglia (DRG) neurons cultured in the presence of a REST-expressing adenovirus showed 7.39±0.11 fold (p≤0.05) increased REST protein, which led to a concomitant 2.20±0.09 fold (p≤0.05) decrease in KCNQ2 protein and a corresponding 7.65±0.49 fold (p≤0.01) reduction in M-current in DRG neurons, compared to vehicle control. We further show that REST protein expression was increased 3.65±0.80 fold in cultured DRG neurons in response to inflammatory stimulation (1 μM bradykinin, 1 μM histamine, 1 μM ATP, 10 μM PAR2-AP and 1 μM substance P for 48 hrs). Increases in REST correlated with a 1.76±0.38 (p≤0.05) fold decrease in KCNQ2 immunoreactivity. Similarly we observed a significant increase in REST mRNA (2.11±0.01 fold) and protein levels and a reciprocal downregulation of KCNQ2 (1.75±0.07 fold) and KCNQ3 (1.43±0.01 fold) transcripts in DRGs from animals with neuropathic nerve injury (partial sciatic nerve lesion, PSNL). We propose that transcriptional regulation of KCNQ channels by REST will have profound effects on neuronal excitability and may contribute to the mechanisms of peripheral sensitisation in chronic pain.