Appearance of Water Channels in Xenopus Oocytes Expressing Red Cell CHIP28 Protein

Abstract

Water rapidly crosses the plasma membrane of red blood cells (RBCs) and renal tubules through specialized channels. Although selective for water, the molecular structure of these channels is unknown. The CHIP28 protein is an abundant integral membrane protein in mammalian RBCs and renal proximal tubules and belongs to a family of membrane proteins with unknown functions. Oocytes from Xenopus laevis microinjected with in vitro-transcribed CHIP28 RNA exhibited increased osmotic water permeability; this was reversibly inhibited by mercuric chloride, a known inhibitor of water channels. Therefore it is likely that CHIP28 is a functional unit of membrane water channels.

Expression and functional analysis of the rice plasma-membrane intrinsic protein gene family

“…Aquaporins play a significant role in recovery from water deficit in both prokaryotic and eukaryotic cells [1,38]. Expression of aquaporin genes are regulated under water stress treatments in many plant species [17,18,[20][21][22].…”

“…Transmembrane water transport occurs by diffusion through the lipid bilayer and/or by increased membrane permeability due to the water channel proteins, aquaporins [1]. The presence of aquaporins, a class of major intrinsic proteins (MIPs), enables fast and controlled translocation of water across the membrane.…”

Functional expression of the human CHIP28 water channel in a yeast secretory mutant

“…The estimated number of functional C!-IIP28 molecules per vesicle is (~13, considering that the siagle water channel Pf is 6.8-16 x 10 -~4 cm3/s [6,9], the vesicle slrface area is 3.14x 10 -~° cm 2 and that APf (defined as C HIP28-containing vesicle Pf-control vesicle Pf) is 2.8 x 10 .3 c~ ~/s. Several water channel characteristics were verified, in p,.rticular a low activation energy value and sensitivity to a cl tssical mercurial sulfhydryl reagent.…”

“…The functional characterization of CHIP28 has so far been essentially performed by micro-injecting in vitro-transcribed cRNA into Xenopus laevis oocytes [6] and by reconstituting purified CHIP28 into proteoliposomes [7][8][9]. In the present work, we investigated a new heterologous expression system for CHIP28 production and functional analysis: a Saccharomyces cerevisiae temperature-sensitive mutant strain, defective in the final step of the secretory pathway (sec mutant) [10], which has already been successfully used for the expression of membrane proteins [11][12][13].…”

Role of transpiration in arsenic accumulation of hyperaccumulator Pteris vittata L.

“…Based on results from the present study, this carrier may be closely related to water uptake. The earlier view is that water molecules enter into cells through passive diffusion, but recently, it has been suggested that some specialized water transport carriers like aquaglyceroporins play an important role (Luu and Maurel 2005;Preston et al 1992). The aquaglyceroporins, a class of water channel not only permeable to water molecules but also permeable to glycerol and small solutes (Thomas et al 2002), have been identified as carriers of As in bacteria, yeast, humans, and other vertebrates (Mukhopadhyay et al 2014) but not found in the As hyperaccumulator yet (Mathews et al 2011).…”