Activation of the Caenorhabditis elegans Degenerin Channel by Shear Stress Requires the MEC-10 Subunit

Abstract

Mechanotransduction in Caenorhabditis elegans touch receptor neurons is mediated by an ion channel formed by MEC-4, MEC-10, and accessory proteins. To define the role of these subunits in the channel's response to mechanical force, we expressed degenerin channels comprising MEC-4 and MEC-10 in Xenopus oocytes and examined their response to laminar shear stress (LSS). Shear stress evoked a rapid increase in whole cell currents in oocytes expressing degenerin channels as well as channels with a MEC-4 degenerin mutation (MEC-4d), suggesting that C. elegans degenerin channels are sensitive to LSS. MEC-10 is required for a robust LSS response as the response was largely blunted in oocytes expressing homomeric MEC-4 or MEC-4d channels. We examined a series of MEC-10/MEC-4 chimeras to identify specific domains (amino terminus, first transmembrane domain, and extracellular domain) and sites (residues 130 -132 and 134 -137) within MEC-10 that are required for a robust response to shear stress. In addition, the LSS response was largely abolished by MEC-10 mutations encoded by a touch-insensitive mec-10 allele, providing a correlation between the channel's responses to two different mechanical forces. Our findings suggest that MEC-10 has an important role in the channel's response to mechanical forces.

Sensory experience controls dendritic structure and behavior by distinct pathways involving degenerins

“…These findings suggest that these two proteins are required for the isolation-induced morphological modification of the PVD and represent an example in which the response to harsh touch is independent of the structural alteration of the PVD. Since MEC-10 is important for laminar shear stress 41 and touch 21 we suggest that this channel and its possible partners from the DEG/ENaC family, such as DEGT-1, ASIC-1 and DEL-1 25, 43, 44 , affect the structure and the function of the PVD independently, in an experience-dependent manner and contrary to the original hypothesis by Hall and Treinin 39 .…”

“…Thus, the structure of the PVD is sensitive to activity and cation influx via DEG/ENaCs. To determine whether the morphological effect on PVD structure is also mediated by mechanical (like friction 41 and collisions 21 ), rather than chemical cues, we used glass beads under isolated conditions, to test the effect on the morphology. We found that mechano-stimulation induced by glass beads did not restore the fraction of ectopic branching, but it did significantly increase the number of straight quaternary branches and decreased the percentage of self-avoidance defects (compared with isolated animals without beads, Fig.…”

Mechanical activation of epithelial Na+channel relies on an interdependent activity of the extracellular matrix and extracellularN-glycans of αENaC

“…In contrast to other cell lines, oocytes have a native and differentiated ECM that is not challenged by passaging during cultivation. They are also an established model for investigating the effects of SF on ENaC (Carattino et al, 2004;Althaus et al, 2007), K + channels (Hoger et al, 2002), and MEC channels (Shi et al, 2016).…”

Expression and Analysis of Flow-regulated Ion Channels in Xenopus Oocytes

“…Recently, we employed this technique to examine the regulation of MEC-4 and MEC-10 by LSS. These channel forming subunits are members of the ENaC/degenerin family expressed in C. elegans that are required for gentle touch in worms (Driscoll and Chalfie, 1991; Shi et al , 2016). Other investigators have employed the technique describe here to study the response of K + channels expressed in the vasculature to LSS (Hoger et al , 2002; Fronius et al , 2010).…”

“…Epithelial and endothelial cells are exposed to laminar shear stress (LSS), a tangential force exerted by flowing fluids against the wall of vessels and epithelia. The protocol outlined herein has been used to examine the response of ion channels expressed in Xenopus oocytes to LSS (Hoger et al , 2002; Carattino et al , 2004; Shi et al , 2006). The Xenopus oocyte is a reliable system that allows for the expression and chemical modification of ion channels and regulatory proteins (George et al , 1989; Palmer et al , 1990; Sheng et al , 2001; Carattino et al , 2003).…”