Mechanosensitive Ion Channels in Cultured Sensory Neurons of Neonatal Rats

Abstract

Mechanosensitive (MS) ion channels are present in a variety of cells. However, very little is known about the ion channels that account for mechanical sensitivity in sensory neurons. We identified the two most frequently encountered but distinct types of MS channels in 1390 of 2962 membrane patches tested in cultured dorsal root ganglion neurons. The two MS channels exhibited different thresholds, thus named as low-threshold (LT) and high-threshold (HT) MS channels, and sensitivity to pressure. The two channels retained different single-channel conductances and current-voltage relationships: LT and HT channels elicited large- and small-channel conductance with outwardly rectifying and linear I-V relationships, respectively. Both LT and HT MS channels were permeable to monovalent cations and Ca2+ and were blocked by gadolinium, a blocker of MS channels. Colchicine and cytochalasin D markedly reduced the activities of the two MS channels, indicating that cytoskeletal elements support the mechanosensitivity. Both types of MS channels were found primarily in small sensory neurons with diameters of <30 microm. Furthermore, HT MS channels were sensitized by a well known inducer of mechanical hyperalgesia, prostaglandin E2, via the protein kinase A pathway. We identified two distinct types of MS channels in sensory neurons that probably give rise to the observed MS whole-cell currents and transduce mechanical stimuli to neural signals involved in somatosensation, including pain.

TACAN is an essential component of the mechanosensitive ion channel responsible for pain sensing

“…7, 2018; evoked current did not affect the channel activation threshold (-37.1 + 3.2 mm Hg, n=47) or the percentage of active patches (82%, 47 of 57 patches). This elevated activation threshold is similar to that observed in cultured primary nociceptors (Cho et al, 2002), also known as high-threshold mechanonociceptors, highlighting another similarity between TACAN and the endogenous channel found in nociceptors. In stably transfected CHO cells, we determined the single-channel conductance of the MSC induced by TACAN proteins.…”

“…A different MSC, termed Piezo2, plays a crucial role in sensing touch but not mechanical pain (Ranade et al, 2014b). Moreover, Piezo2 displays rapid adapting kinetics and a higher conductance than the one identified in nociceptors (Cho et al, 2006;Cho et al, 2002;Coste et al, 2010). In contrast, TACAN displays slow-adapting kinetics, lower conductance, and when its expression is reduced, leaves responses to touch intact but impairs those to mechanical pain.…”

Actin Filaments Mediate Mechanical Gating during Osmosensory Transduction in Rat Supraoptic Nucleus Neurons

“…Previous studies have indicated that filamentous actin (Factin) can either participate in the gating of mechanosensitive channels (Su et al, 2000;Cho et al, 2002;Piao et al, 2003) or protect against their activation by mechanical stimuli by providing physical support for the plasma membrane (Hamill and McBride, 1997;Ko and McCulloch, 2000;Morris, 2001). To determine whether F-actin is required for mechanical regulation of SIC channels, we quantified transducer sensitivity in MNCs pretreated (30 -60 min) with Cyt-D (200 -250 M), a drug that depolymerizes F-actin (Cooper, 1987), or JSK (2.5 M), a drug that promotes actin polymerization (Bubb et al, 1994).…”

Transient Receptor Potential Vanilloid 1 Is Required for Intrinsic Osmoreception in Organum Vasculosum Lamina Terminalis Neurons and for Normal Thirst Responses to Systemic Hyperosmolality

“…The mean reversal potential of the osmotically evoked current was Ϫ27.6 Ϯ 4.5 mV, consistent with the involvement of nonselective cation channels under our experimental conditions (see Discussion). Additionally, increases in membrane conductance induced by hyperosmolality could be reversed by bath application of 300 M Gd 3ϩ (⌬G ϭ 0.51 Ϯ 0.15 nS before and ⌬G ϭ Ϫ0.16 Ϯ 0.06 nS after Gd 3ϩ ; n ϭ 8; p ϭ 0.003; data not shown), a blocker of nonselective cation channels (Hase et al, 1995;Cho et al, 2002).…”