Membrane ion transport in non-excitable tissues.

Keith Nehrke

doi:10.1895/wormbook.1.174.1

Abstract

The facilitated movement of ions across cell membranes can be characterized as occurring through active (ATP-dependent), secondary active (coupled), or passive transport processes. Each of these processes is mediated by a diverse group of membrane proteins. Over the past fifteen years, studies of membrane transport in C. elegans have benefited from the fact that worms are anatomically simple, easily and economically cultured, and genetically tractable. These experimental advantages have been instrumental in defining how membrane transport processes contribute to whole organism physiology. The focus of this review is to survey the recent advances in our understanding of membrane transport that have arisen from integrative physiological approaches in the nematode C. elegans.

Highlights

The ability to form and maintain membrane electrochemical gradients is fundamental to life
Membrane ion transport in non-excitable tissues Subsequently, it has been discovered that a wave of Ca2+ initiates in the posterior intestinal cells and propagates forward through the intestine concomitant with execution of the defecation motor program (DMP) (Figure 2; Movie 2); several parallel approaches that utilized isolated intact intestinal preparations loaded with Ca2+ sensitive dyes or live worms expressing fluorescent Genetically Encoded Ca2+ Indicator (GECI) combined with dynamic imaging techniques have corroborated this finding (Espelt et al, 2005; Norman et al, 2005; Teramoto et al, 2006; Peters et al, 2007; Nehrke et al, 2008)
Since mir-786 acts upstream of the IP3R, which is the central molecular pacemaker for defecation, it is possible that fatty acids directly influence the IP3R's activity (Kemp et al, 2012). These results suggest that mir-786 is an amplifier of Ca2+ signaling

Summary

Introduction

The ability to form and maintain membrane electrochemical gradients is fundamental to life. Membrane ion transport in non-excitable tissues Subsequently, it has been discovered that a wave of Ca2+ initiates in the posterior intestinal cells and propagates forward through the intestine concomitant with execution of the DMP (Figure 2; Movie 2); several parallel approaches that utilized isolated intact intestinal preparations loaded with Ca2+ sensitive dyes or live worms expressing fluorescent GECIs combined with dynamic imaging techniques have corroborated this finding (Espelt et al, 2005; Norman et al, 2005; Teramoto et al, 2006; Peters et al, 2007; Nehrke et al, 2008). Ca2+ oscillations in the worm intestine appear to be supported by non-canonical store-independent Ca2+ entry pathways Despite these findings, the specific role of GON-2 and GTL-1 in regulating defecation has been debated and their loss-of-function defecation phenotypes have been suggested to result indirectly from defects in magnesium absorption (Teramoto et al, 2005). In a now-routine example of mechanistic convergence between worms and mammals, both Stim and Orai have recently been shown to function in oocyte meiotic maturation in mice (Cheon et al, 2013)

Non-neuronal contributions to the locomotor circuit

Epidermal wound closure

Proton signaling

Osmotic balance: the art of adaptation

Conclusion