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Membranes, Volume 4, Issue 4 (December 2014) – 6 articles , Pages 642-777

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1959 KiB

Open AccessArticle

Structure of a Sialo-Oligosaccharide from Glycophorin in Carp Red Blood Cell Membranes

by Takahiko Aoki, Kenji Chimura, Hikaru Sugiura and Yasuko Mizuno

Membranes 2014, 4(4), 764-777; https://doi.org/10.3390/membranes4040764 - 13 Nov 2014

Cited by 1 | Viewed by 5879

Abstract

We isolated a high-purity carp glycophorin from carp erythrocyte membranes and prepared the oligosaccharide fraction from glycophorin by β-elimination [1]. The oligosaccharide fraction was separated into two components (P-1 and P-2) using a Glyco-Pak DEAE column. These O-linked oligosaccharides (P-1 and P-2) were composed of glucose, galactose, fucose, N-acetylgalactosamine and N-glycolylneuraminic acid (NeuGc). The P-1 and P-2 contained one and two NeuGc residues, respectively, and the P-1 exhibited bacteriostatic activity [1]. Using NMR and GC-MS, we determined that the structure of the bacteriostatic P-1 was NeuGcα2→6 (Fucα1→4) (Glcα1→3) Galβ1→4GalNAc-ol. This O-linked oligosaccharide was unique for a vertebrate with respect to the hexosamine and hexose linkages and its non-chain structure. Full article

(This article belongs to the Section Biological Membrane Composition and Structures)

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606 KiB

Open AccessReview

The Role of the Clathrin Adaptor AP-1: Polarized Sorting and Beyond

by Fubito Nakatsu, Koji Hase and Hiroshi Ohno

Membranes 2014, 4(4), 747-763; https://doi.org/10.3390/membranes4040747 - 07 Nov 2014

Cited by 41 | Viewed by 11355

Abstract

The selective transport of proteins or lipids by vesicular transport is a fundamental process supporting cellular physiology. The budding process involves cargo sorting and vesicle formation at the donor membrane and constitutes an important process in vesicular transport. This process is particularly important for the polarized sorting in epithelial cells, in which the cargo molecules need to be selectively sorted and transported to two distinct destinations, the apical or basolateral plasma membrane. Adaptor protein (AP)-1, a member of the AP complex family, which includes the ubiquitously expressed AP-1A and the epithelium-specific AP-1B, regulates polarized sorting at the trans-Golgi network and/or at the recycling endosomes. A growing body of evidence, especially from studies using model organisms and animals, demonstrates that the AP-1-mediated polarized sorting supports the development and physiology of multi-cellular units as functional organs and tissues (e.g., cell fate determination, inflammation and gut immune homeostasis). Furthermore, a possible involvement of AP-1B in the pathogenesis of human diseases, such as Crohn’s disease and cancer, is now becoming evident. These data highlight the significant contribution of AP-1 complexes to the physiology of multicellular organisms, as master regulators of polarized sorting in epithelial cells. Full article

(This article belongs to the Special Issue Trafficking of Membrane Receptors)

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1546 KiB

Open AccessArticle

Flexibility in the Insulin Receptor Ectodomain Enables Docking of Insulin in Crystallographic Conformation Observed in a Hormone-Bound Microreceptor

by Harish Vashisth

Membranes 2014, 4(4), 730-746; https://doi.org/10.3390/membranes4040730 - 10 Oct 2014

Cited by 7 | Viewed by 7439

Abstract

Insulin binding to the insulin receptor (IR) is the first key step in initiating downstream signaling cascades for glucose homeostasis in higher organisms. The molecular details of insulin recognition by IR are not yet completely understood, but a picture of hormone/receptor interactions at one of the epitopes (Site 1) is beginning to emerge from recent structural evidence. However, insulin-bound structures of truncated IR suggest that crystallographic conformation of insulin cannot be accommodated in the full IR ectodomain due to steric overlap of insulin with the first two type III fibronectin domains (F1 and F2), which are contributed to the insulin binding-pocket by the second subunit in the IR homodimer. A conformational change in the F1-F2 pair has thus been suggested. In this work, we present an all-atom structural model of complex of insulin and the IR ectodomain, where no structural overlap of insulin with the receptor domains (F1 and F2) is observed. This structural model was arrived at by flexibly fitting parts of our earlier insulin/IR all-atom model into the simulated density maps of crystallized constructs combined with conformational sampling from apo-IR solution conformations. Importantly, our experimentally-consistent model helps rationalize yet unresolved Site Full article

(This article belongs to the Special Issue Structure and Function of Membrane Receptors)

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1670 KiB

Open AccessReview

Membrane Bioprocesses for Pharmaceutical Micropollutant Removal from Waters

by Matthias De Cazes, Ricardo Abejón, Marie-Pierre Belleville and José Sanchez-Marcano

Membranes 2014, 4(4), 692-729; https://doi.org/10.3390/membranes4040692 - 06 Oct 2014

Cited by 71 | Viewed by 10544

Abstract

The purpose of this review work is to give an overview of the research reported on bioprocesses for the treatment of domestic or industrial wastewaters (WW) containing pharmaceuticals. Conventional WW treatment technologies are not efficient enough to completely remove all pharmaceuticals from water. Indeed, these compounds are becoming an actual public health problem, because they are more and more present in underground and even in potable waters. Different types of bioprocesses are described in this work: from classical activated sludge systems, which allow the depletion of pharmaceuticals by bio-degradation and adsorption, to enzymatic reactions, which are more focused on the treatment of WW containing a relatively high content of pharmaceuticals and less organic carbon pollution than classical WW. Different aspects concerning the advantages of membrane bioreactors for pharmaceuticals removal are discussed, as well as the more recent studies on enzymatic membrane reactors to the depletion of these recalcitrant compounds. Full article

(This article belongs to the Special Issue Membrane Bioprocesses and Bioreactors)

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369 KiB

Open AccessArticle

Potentialities of a Membrane Reactor with Laccase Grafted Membranes for the Enzymatic Degradation of Phenolic Compounds in Water

by Vorleak Chea, Delphine Paolucci-Jeanjean, José Sanchez and Marie-Pierre Belleville

Membranes 2014, 4(4), 678-691; https://doi.org/10.3390/membranes4040678 - 06 Oct 2014

Cited by 7 | Viewed by 5525

Abstract

This paper describes the degradation of phenolic compounds by laccases from Trametes versicolor in an enzymatic membrane reactor (EMR). The enzymatic membranes were prepared by grafting laccase on a gelatine layer previously deposited onto α-alumina tubular membranes. The 2,6-dimethoxyphenol (DMP) was selected from among the three different phenolic compounds tested (guaiacol, 4-chlorophenol and DMP) to study the performance of the EMR in dead end configuration. At the lowest feed substrate concentration tested (100 mg·L⁻¹), consumption increased with flux (up to 7.9 × 10³ mg·h⁻¹·m⁻²at 128 L·h⁻¹·m⁻²), whereas at the highest substrate concentration (500 mg·L⁻¹), it was shown that the reaction was limited by the oxygen content. Full article

(This article belongs to the Special Issue Membrane Bioprocesses and Bioreactors)

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1148 KiB

Open AccessReview

The Role of Rab Proteins in Neuronal Cells and in the Trafficking of Neurotrophin Receptors

by Cecilia Bucci, Pietro Alifano and Laura Cogli

Membranes 2014, 4(4), 642-677; https://doi.org/10.3390/membranes4040642 - 06 Oct 2014

Cited by 62 | Viewed by 14944

Abstract

Neurotrophins are a family of proteins that are important for neuronal development, neuronal survival and neuronal functions. Neurotrophins exert their role by binding to their receptors, the Trk family of receptor tyrosine kinases (TrkA, TrkB, and TrkC) and p75NTR, a member of the tumor necrosis factor (TNF) receptor superfamily. Binding of neurotrophins to receptors triggers a complex series of signal transduction events, which are able to induce neuronal differentiation but are also responsible for neuronal maintenance and neuronal functions. Rab proteins are small GTPases localized to the cytosolic surface of specific intracellular compartments and are involved in controlling vesicular transport. Rab proteins, acting as master regulators of the membrane trafficking network, play a central role in both trafficking and signaling pathways of neurotrophin receptors. Axonal transport represents the Achilles' heel of neurons, due to the long-range distance that molecules, organelles and, in particular, neurotrophin-receptor complexes have to cover. Indeed, alterations of axonal transport and, specifically, of axonal trafficking of neurotrophin receptors are responsible for several human neurodegenerative diseases, such as Huntington’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis and some forms of Charcot-Marie-Tooth disease. In this review, we will discuss the link between Rab proteins and neurotrophin receptor trafficking and their influence on downstream signaling pathways. Full article

(This article belongs to the Special Issue Trafficking of Membrane Receptors)

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