Studies of water permeability and proteins of erythrocyte membranes in patients with Duchenne muscular dystrophy

Comparative studies of water permeability of red blood cells from humans and over 30 animal species: an overview of 20 years of collaboration with Philip Kuchel

NMR measurements of the diffusional permeability of the human adult red blood cell (RBC) membrane to water (P(d)) and of the activation energy (E(a,d)) of the process furnished values of P(d) ~ 4 × 10(-3) cm/s at 25 °C and ~6.1 × 10(-3) cm/s at 37 °C, and E(a,d) ~ 26 kJ/mol. Comparative NMR measurements for other species showed: (1) monotremes (echidna and platypus), chicken, little penguin, and saltwater crocodile have the lowest P(d) values; (2) sheep, cow, and elephant have P(d) values lower than human P(d) values; (3) cat, horse, alpaca, and camel have P(d) values close to those of humans; (4) guinea pig, dog, dingo, agile wallaby, red-necked wallaby, Eastern grey kangaroo, and red kangaroo have P(d) values higher than those of humans; (5) mouse, rat, rabbit, and "small and medium size" marsupials have the highest values of P(d) (>8.0 × 10(-3) cm/s at 25 °C and >10.0 × 10(-3) cm/s at 37 °C). There are peculiarities of E(a,d) values for the RBCs from different species. The maximum inhibition of diffusional permeability of RBCs induced by incubation with p-chloromercuribenzene sulfonate varied between 0% (for the chicken and little penguin) to ~50% (for human, mouse, cat, sheep, horse, camel, and Indian elephant), and ~60-75% (for rat, guinea pig, rabbit, dog, alpaca, and all marsupials). These results indicate that no water channel proteins (WCPs) or aquaporins are present in the membrane of RBCs from monotremes (echidna, platypus), chicken, little penguin and saltwater crocodile whereas WCPs from the membranes of RBCs from marsupials have peculiarities.

The first discovered water channel protein, later called aquaporin 1: molecular characteristics, functions and medical implications

After a decade of work on the water permeability of red blood cells (RBC) Benga group in Cluj-Napoca, Romania, discovered in 1985 the first water channel protein in the RBC membrane. The discovery was reported in publications in 1986 and reviewed in subsequent years. The same protein was purified by chance by Agre group in Baltimore, USA, in 1988, who called in 1991 the protein CHIP28 (CHannel forming Integral membrane Protein of 28 kDa), suggesting that it may play a role in linkage of the membrane skeleton to the lipid bilayer. In 1992 the Agre group identified CHIP28's water transport property. One year later CHIP28 was named aquaporin 1, abbreviated as AQP1. In this review the molecular structure-function relationships of AQP1 are presented. In the natural or model membranes AQP1 is in the form of a homotetramer, however, each monomer has an independent water channel (pore). The three-dimensional structure of AQP1 is described, with a detailed description of the channel (pore), the molecular mechanisms of permeation through the channel of water molecules and exclusion of protons. The permeability of the pore to gases (CO(2), NH(3), NO, O(2)) and ions is also mentioned. I have also reviewed the functional roles and medical implications of AQP1 expressed in various organs and cells (microvascular endothelial cells, kidney, central nervous system, eye, lacrimal and salivary glands, respiratory apparatus, gastrointestinal tract, hepatobiliary compartments, female and male reproductive system, inner ear, skin). The role of AQP1 in cell migration and angiogenesis in relation with cancer, the genetics of AQP1 and mutations in human subjects are also mentioned. The role of AQP1 in red blood cells is discussed based on our comparative studies of water permeability in over 30 species.

Water channel proteins (later called aquaporins) and relatives: past, present, and future

Water channels or water channel proteins (WCPs) are transmembrane proteins that have a specific three-dimensional structure with a pore that can be permeated by water molecules. WCPs are large families (over 450 members) that are present in all kingdoms of life. The first WCP was discovered in the human red blood cell (RBC) membrane in 1980s. In 1990s other WCPs were discovered in plants, microorganisms, various animals, and humans; and it became obvious that the WCPs belong to the superfamily of major intrinsic proteins (MIPs, over 800 members). WCPs include three subfamilies: (a) aquaporins (AQPs), which are water specific (or selective water channels); (b) aquaglyceroporins (and glycerol facilitators), which are permeable to water and/or other small molecules; and (c) "superaquaporins" or subcellular AQPs. WCPs (and MIPs) have several structural characteristics which were better understood after the atomic structure of some MIPs was deciphered. The structure-function relationships of MIPs expressed in microorganisms (bacteria, archaea, yeast, and protozoa), plants, and some multicellular animal species [nematodes, insects, fishes, amphibians, mammals (and humans)] are described. A synthetic overview on the WCPs from RBCs from various species is provided. The physiological roles of WCPs in kidney, gastrointestinal system, respiratory apparatus, central nervous system, eye, adipose tissue, skin are described, and some implications of WCPs in various diseases are briefly presented. References of detailed reviews on each topic are given. This is the first review providing in a condensed form an overview of the whole WCP field that became in the last 20 years a very hot area of research in biochemistry and molecular cell biology, with wide and increasing implications.

Water transport in human red cells: effects of 'non-inhibitory' sulfhydryl reagents

The water diffusional permeability of human red blood cells following exposure to various sulfhydryl group (SH) reagents have been studied using a nuclear magnetic resonance technique. Exposure of red blood cells up to 12 mM N-ethylmaleimide (NEM) or 10 mM 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNE) alone does not affect water diffusion. In contrast, when DTNB treatment follows a preincubation of the cells with NEM, a small (18% at 37 degrees C) but significant inhibition of water permeability occurs. The NEM and DTNB treatment of the cells caused no change of the cell shape and volume or of the cell water volume. Consequently, the inhibition observed after NEM and DTNB treatment has a real significance.

The basal permeability to water of human red blood cells evaluated by a nuclear magnetic resonance technique

The characteristics of water diffusional permeability (P) of human red blood cells were studied on isolated erythrocytes by a doping nuclear magnetic resonance technique. In order to estimate the basal permeability the maximal inhibition of water diffusion was induced by exposure of red blood cells to p-chloromercuribenzene sulfonate (PCMBS) under various conditions (concentration, duration, temperature). The lowest values of P were around 0.7 X 10(-3) cm s-1 at 10 degrees C, 1.2 X 10(-3) cm s-1 at 15 degrees C, 1.4 X 10(-3) cm s-1 at 20 degrees C, 1.8 X 10(-3) cm s-1 at 25 degrees C, 2.1 X 10(-3) cm s-1 at 30 degrees C and 3.5 X 10(-3) cm s-1 at 37 degrees C. The mean value of the activation energy of water diffusion (Ea,d) was 25 kJ/mol for control and 43.7 kJ/mol for PCMBS--inhibited erythrocytes. The values of P and Ea,d obtained after induction of maximal inhibition of water diffusion by PCMBS can be taken as references for the basal permeability to water of the human red blood cell membrane.