Differential involvement of gangliosides versus phospholipids in the process of temperature adaptation in vertebrates. A comparative phenomenological and physicochemical study

The dynamics and role of sphingolipids in eukaryotic organisms upon thermal adaptation

All living beings have an optimal temperature for growth and survival. With the advancement of global warming, the search for understanding adaptive processes to climate changes has gained prominence. In this context, all living beings monitor the external temperature and develop adaptive responses to thermal variations. These responses ultimately change the functioning of the cell and affect the most diverse structures and processes. One of the first structures to detect thermal variations is the plasma membrane, whose constitution allows triggering of intracellular signals that assist in the response to temperature stress. Although studies on this topic have been conducted, the underlying mechanisms of recognizing thermal changes and modifying cellular functioning to adapt to this condition are not fully understood. Recently, many reports have indicated the participation of sphingolipids (SLs), major components of the plasma membrane, in the regulation of the thermal stress response. SLs can structurally reinforce the membrane or/and send signals intracellularly to control numerous cellular processes, such as apoptosis, cytoskeleton polarization, cell cycle arresting and fungal virulence. In this review, we discuss how SLs synthesis changes during both heat and cold stresses, focusing on fungi, plants, animals and human cells. The role of lysophospholipids is also discussed.

Biological roles of glycans

Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.

Abiotic stress of ambient cold temperature regulates the host receptivity to pathogens by cell surfaced sialic acids

Ambient cold temperature, as an abiotic stress, regulates the survival, stability, transmission, and infection of pathogens. However, the effect of cold temperature on the host receptivity to the pathogens has not been fully studied. In this study, the expression of terminal α-2,3- and α-2,6-sialic acids were increased in murine lung tissues, especially bronchial epithelium, by exposure to cold condition. The expression of several sialyltransferases were also increased by exposure to cold temperature. Furthermore, in human bronchial epithelial BEAS-2B cells, the expressions of α-2,3- and α-2,6-sialic acids, and mRNA levels of sialyltransferases were increased in the low temperature condition at 33 °C. On the other hand, the treatment of Lith-Gly, a sialyltransferase inhibitor, blocked the cold-induced expression of sialic acids on surface of BEAS-2B cells. The binding of influenza H1N1 hemagglutinin (HA) toward BEAS-2B cells cultured at low temperature condition was increased, compared to 37 °C. In contrast, the cold-increased HA binding was blocked by treatment of lithocholicglycine and sialyl-N-acetyl-D-lactosamines harboring α-2,3- and α-2,6-sialyl motive. These results suggest that the host receptivity to virus at cold temperature results from the expressions of α-2,3- and α-2,6-sialic acids through the regulation of sialyltransferase expression.

Influenza A virus survival in water is influenced by the origin species of the host cell

Background

Influenza A viruses have an envelope made of a lipid bilayer and two surface glycoproteins, the hemagglutinin and the neuraminidase. The structure of the virus is directly dependent on the genetic makeup of the viral genome except the glycosylation moieties and the composition of the lipid bilayer. They both depend on the host cell and are in direct contact with the environment, such as air or water. Virus survival is important for virus transmission from contaminated waters in the case of wild aquatic birds or from contaminated surface or air for humans.

Objective

The objective of this study was to check whether the origin species of the host cell has an influence on influenza A virus survival.

Method

The persistence in water at 35°C of viruses grown on either mammalian cells or avian cells and belonging to two different subtypes H1N1 and H5N1 was compared.

Results

Both H5N1 and H1N1 viruses remained infectious for periods of time as long as 19–25 days, respectively. However, within the same subtype, viruses grown on mammalian cells were more stable in water at 35°C than their counterparts grown on avian cells, even for viruses sharing the same genetic background.

Conclusions

This difference in virus stability outside the host is probably connected to the nature of the lipid bilayer taken from the cell or to the carbohydrate side chains of the virus surface glycoproteins. Moreover, the long-lasting survival time might have a critical role in the ecology of influenza viruses, especially for avian viruses.

Distribution of mono-, di- and trisialo gangliosides in the brain of Actinopterygian fishes

BACKGROUND

Mono-, di- and trisialo gangliosides are major glycosphingolipids in the brain of higher vertebrates involved in lipid raft assembly. In contrast, the fish brain is abundant in polisialo-gangliosides, whose function is implicated in the modulation of repulsive and attractive intercellular interactions during embryonic development and a temperature adaptation process. The histological distribution of gangliosides is usually studied in rodent and mammalian brains, but to date it has not been described in the case of fish brain.

METHODS

Gangliosides were extracted from adult brains of trout, carp and zebrafish and separated by TLC. High-affinity anti-ganglioside (GM1, GD1a, GD1b, GT1b) IgG antibodies were used for immunohistochemistry.

RESULTS

In trout and carp brains GM1 and GT1b are expressed in the same neuronal cell bodies from the telencephalon to the spinal cord. In zebrafish brain GM1 was not detected, whereas GT1b is a general neuropil staining. GD1a is specific for unmyelinated parallel fibers in carp and zebrafish brains as well as parallel fibers in the molecular layer of all cerebellar divisions. In trout brain GD1b is found in parallel fibers of the cerebellum, but not in the tectum mesencephali. GD1b is expressed in zebrafish neuronal cell bodies.

CONCLUSIONS

Each studied species has a different expression of complex gangliosides. GT1b is widely present, whereas GD1a and GD1b appear in a specific group of unmyelinated fibers and could be used as their specific marker.

GENERAL SIGNIFICANCE

This is the first report on mono-, di- and trisialo ganglioside (GM1, GD1a, GD1b and GT1b) distribution in the brain of adult Actinopterygian fishes. This article is part of a Special Issue entitled Glycoproteomics.

Pathophysiological actions of neuropathy-related anti-ganglioside antibodies at the neuromuscular junction

The outer leaflet of neuronal membranes is highly enriched in gangliosides. Therefore, specific neuronal roles have been attributed to this family of sialylated glycosphingolipids, e.g. in modulation of ion channels and transporters, neuronal interaction and recognition, temperature adaptation, Ca(2+) homeostasis, axonal growth, (para)node of Ranvier stability and synaptic transmission. Recent developmental, ageing and injury studies on transgenic mice lacking subsets of gangliosides indicate that gangliosides are involved in maintenance rather than development of the nervous system and that ganglioside family members are able to act in a mutually compensatory manner. Besides having physiological functions, gangliosides are the likely antigenic targets of autoantibodies present in Guillain-Barré syndrome (GBS), a group of neuropathies with clinical symptoms of motor- and/or sensory peripheral nerve dysfunction. Antibody binding to peripheral nerves is thought to either interfere with ganglioside function or activate complement, causing axonal damage and thereby disturbed action potential conduction. The presynaptic motor nerve terminal at the neuromuscular junction (NMJ) may be a prominent target because it is highly enriched in gangliosides and lies outside the blood-nerve barrier, allowing antibody access. The ensuing neuromuscular synaptopathy might contribute to the muscle weakness in GBS patients. Several groups, including our own, have studied the effects of anti-ganglioside antibodies in ex vivo and in vivo experimental settings at mouse NMJs. Here, after providing a background overview on ganglioside synthesis, localization and physiology, we will review those studies, which clearly show that anti-ganglioside antibodies are capable of binding to NMJs and thereby can exert a variety of pathophysiological effects. Furthermore, we will discuss the human clinical electrophysiological and histological evidence produced so far of the existence of a neuromuscular synaptopathy contributing to muscle weakness in GBS patients.

Neuromuscular synaptic transmission in aged ganglioside-deficient mice

Gangliosides are sialylated glycosphingolipids that are present in high density on neuronal membranes, especially at synapses, where they are assumed to play functional or modulating roles. Mice lacking GM2/GD2-synthase express only the simple gangliosides GD3 and GM3 and develop progressive motor behaviour deficits upon ageing, apparently due to failing complex ganglioside-dependent maintenance and/or repair processes or, alternatively, toxic GM3/GD3 accumulation. We investigated the function of neuromuscular junctions (NMJs) of aged (>9 month-old) GM2/GD2-synthase null-mutant mice, because synaptic dysfunction might develop with age and could potentially contribute to the late-onset motor phenotype. In addition, we studied NMJs of old mice lacking GD3-synthase (expressing only O- and a-series gangliosides), which do not show an overt neurological phenotype but may develop subclinical synaptic deficits. Detailed electrophysiological analyses showed subtle changes in presynaptic neurotransmitter release. Acetylcholine release at 40 Hz nerve stimulation at aged GM2/GD2-synthase null-mutant NMJs ran down slightly more pronounced than at wild-type NMJs, and spontaneous acetylcholine release rate at GD3-synthase null-mutant NMJs was somewhat higher than at wild-type, selectively at 25 °C bath temperature. Interestingly, we observed faster kinetics of postsynaptic electrophysiological responses at aged GD3-synthase null-mutant NMJs, not previously seen by us at NMJs of young GD3-synthase null-mutants or other types of (aged or young) ganglioside-deficient mice. These kinetic changes might reflect a change in postsynaptic acetylcholine receptor behaviour. Our data indicate that it is highly unlikely that transmission failure at NMJs contributes to the progressive motor defects of aged GM2/GD2-synthase null-mutants and that, despite some kinetic changes of synaptic signals, neuromuscular transmission remains successful in aged GD3-synthase null-mutant mice. Apparently, mutual redundancy of the different gangliosides in supporting presynaptic function, as observed previously by us in young mice, remains adequate upon ageing or, alternatively, gangliosides have only relatively little direct impact on neuromuscular synaptic function, even in aged mice.

Neuromuscular synaptic function in mice lacking major subsets of gangliosides

Gangliosides are a family of sialylated glycosphingolipids enriched in the outer leaflet of neuronal membranes, in particular at synapses. Therefore, they have been hypothesized to play a functional role in synaptic transmission. We have measured in detail the electrophysiological parameters of synaptic transmission at the neuromuscular junction (NMJ) ex vivo of a GD3-synthase knockout mouse, expressing only the O- and a-series gangliosides, as well as of a GM2/GD2-synthase*GD3-synthase double-knockout (dKO) mouse, lacking all gangliosides except GM3. No major synaptic deficits were found in either null-mutant. However, some extra degree of rundown of acetylcholine release at high intensity use was present at the dKO NMJ and a temperature-specific increase in acetylcholine release at 35 degrees C was observed in GD3-synthase knockout NMJs, compared with wild-type. These results indicate that synaptic transmission at the NMJ is not crucially dependent on the particular presence of most ganglioside family members and remains largely intact in the sole presence of GM3 ganglioside. Rather, presynaptic gangliosides appear to play a modulating role in temperature- and use-dependent fine-tuning of transmitter output.

The Site of Action of General Anesthetics - A Chemical Approach

Recently Urban (Br. J. Anaesth. 2002, 89, 167) and Trudell (Br. J. Anaesth. 2002, 89, 32) assessed the present state of the art in anesthesiological research. This article is an attempt to add to the discussion some ideas from the chemist's point of view. General anesthesia is a matter of molecular associations. Among the intermolecular interactions that can be involved, weak hydrogen bonding and van der Waals forces are believed to be most important. A pluralistic view is proposed, thereby different anesthetics can choose different interactions in conformity with their chemical structure. This can involve proteins, lipids, and sugars. Special attention is given to glycoproteins and glycosphingolipids. A review with 90 references.

Complex gangliosides at the neuromuscular junction are membrane receptors for autoantibodies and botulinum neurotoxin but redundant for normal synaptic function

One specialization of vertebrate presynaptic neuronal membranes is their multifold enrichment in complex gangliosides, suggesting that these sialoglycolipids may play a major functional role in synaptic transmission. We tested this hypothesis directly by studying neuromuscular synapses of mice lacking complex gangliosides attributable to deletion of the gene coding for beta1,4 GalNAc-transferase (GM2/GD2 synthase), which catalyzes an early step in ganglioside synthesis. Our studies show that complex gangliosides are surprisingly redundant for regulated neurotransmitter release under normal physiological conditions. In contrast, we show that they are membrane receptors for both the paralytic botulinum neurotoxin type-A and human neuropathy-associated anti-ganglioside autoantibodies that arise through molecular mimicry with microbial structures. These data prove the critical importance of complex gangliosides in mediating pathophysiological events at the neuromuscular synapse.

Gangliosides affect membrane-channel activities dependent on ambient temperature

1. The functional properties of biological membranes depend on their molecular composition. In regard to this, charged glycosphingolipids play an outstanding role in the functional adaptation of membranes to different temperatures. 2. In order to shed some light on the respective functional properties of complex membraneous glycosphingolipids, the effects of altered temperatures (5-40 degrees C) on planar lipid bilayers made from diphytanoylphosphatidylcholine (DPPC) and alamethicin as an ion channel was analyzed in the presence of either a sialoglycosphingolipid (less polar disialoganglioside GD1a or highly polar tetrasialoganglioside GQ1b) or phosphatidylserine (PS; as control). 3. Different to the control bilayers made from DPPC or DPPC + PS, the bilayers containing gangliosides had specific maxima in alamethicin conductance and stabile life times. Changes in pore-state conductances indicate structural effects based on an interaction of the large (negatively charged) ganglioside headgroups with the alamethicin pores. 4. The results concerning open time and closed time of channels seem to be based on the gangliosides changing the viscosity of the bilayer and possibly introducing phase transitions. 5. Thus, the findings suggest that gangliosides (1) directly affect channel molecules via their headgroups and (2) may additionally affect the fluidity of membranes in order to maintain membrane homeoviscosity in areas surrounding ion channels independent from the environmental temperature. 6. The effects of gangliosides may be of special interest in describing the ability of neuronal adaptation of vertebrates to temperature and more general regarding the functional adaptation of neurons.

FTIR study of the monosialoganglioside GM1 in perdeuterated dimyristoylglycerophosphocholine (DMPCd54) multilamellar bilayers: spectroscopic evidence of a significant interaction between Ca2+ ions and the sialic acid moiety of GM1

Fourier transform infrared (FTIR) spectroscopy was employed to study bovine brain GM1 and perdeuterated dimyristoylglycerophosphocholine (DMPCd54) multilamellar dispersions (mole fractions of GM1 in DMPCd54: 0.12, 0.15, 0.19, 0.26, 0.34, 0.41, and 0.58), in the absence and presence of 10 mM CaCl2. GM1 micelles did not display a thermal phase transition in the temperature range 5-60 degrees C. Moreover, the ceramide moiety of GM1 inserted into the hydrophobic core of DMPCd54 bilayers and was capable of undergoing a single, cooperative phase transition (Tm = 22-28 degrees C, depending on GM1 content) in a bilayer system. This suggested that the mixed bilayers consisted of a homogeneous mixture and that GM1 was uniformly dispersed in the bilayer plane rather than segregated into regions of relative enrichment. The coexistence of GM1 and DMPCd54 in a bilayer environment induced a rearrangement of the interfacial hydrogen bonding network of the amide I and ester C=O groups, relative to GM1 micelles and DMPCd54 bilayers, respectively. The modifications induced by GM1 might ultimately modulate surface events such as lipid-lipid and/or lipid-protein interactions. The spectroscopic results also suggested that the glycolipid's headgroup surface location and conformation in bilayers allow GM1 to act as a receptor for Ca2+ via its sialic acid moiety.

Cold-induced ependymin expression in zebrafish and carp brain: implications for cold acclimation

Cold acclimation has been suggested to be mediated by alternations in the gene expression pattern in the cold-adapted fish. To investigate the mechanism of cold acclimation in fish brain at the molecular level, relevant subsets of differentially expressed genes of interest were identified and cloned by the PCR-based subtraction suppression hybridization. Characterization of the selected cold-induced cDNA clones revealed one encoding ependymin. This gene was shown to be brain-specific. The expression of ependymin was induced by a temperature shift from 25 degrees C to 6 degrees C in Cyprinus carpio or 12 degrees C in Danio rerio. Activation of ependymin was detected 2 h after cold exposure and peaked at more than 10-fold at 12 h. This peak level remains unchanged until the temperature returns to 25 degrees C. Although the amount of soluble ependymin protein in brain was not changed by cold treatment, its level in the fibrous insoluble polymers increased 2-fold after exposure to low temperature. These findings indicate that the increase in ependymin expression is an early event that may play an important role in the cold acclimation of fish.

Direct electrospray-ionization mass spectrometric analysis of the major ganglioside from crucian carp liver after thin layer chromatography

Ganglioside patterns from crucian carp brain, muscle, and liver as well as liver gangliosides of roach, carp, the cichlid Oreochromis mossambicus, pigeon, dwarf hamster, and calf were comparatively analyzed by high performance thin layer chromatography (HPTLC). To achieve a rapid estimation on potentially interesting ganglioside compounds, electrospray-ionization mass spectrometry (MS) was directly applied to a chloroform/methanol extract of the major TLC band of crucian carp liver. The spectrum, obtained from a few micrograms of this crude biological sample, revealed a series of peaks corresponding to GM4-like monosialoganglioside species. GC-MS analysis revealed hydroxylated fatty acids ranging from 2 h 20 min:0 to 2 h 26 min:0 for the [M'H]- ions of m/z 1061-1145. Collision induced dissociation tandem MS/MS of the major peak with a [M'H]- ion of m/z 1117 demonstrated the presence of N-acetylneuraminic acid as sialic acid compound. The sugar composition was confirmed by GLC as galactose and sialic acid in a 1:1 molar ratio. Thus, the structure of the ion at m/z 1117 is N-acetylneuraminylgalactosylceramide (NeuAc-Gal-Cer) with the long chain base d18:1 and the hydroxylated fatty acid 2 h 24 min:0. The results demonstrate for the first time unambiguously that NeuAc-Gal-Cer is the main ganglioside fraction in fish liver and that electrospray ionization-mass spectrometry (ESI-MS) can be used to elucidate the chemical composition of a ganglioside fraction obtained by convenient extraction of a HPTLC band.