1,721,009 research outputs found
Membrane lipid domains and membrane lipid domain preparations : are they the same thing?
No full textEarly notions on membrane lipid domains were derived mainly from experimental models based on artificial membranes and from studies on membrane fractions prepared by density gradient centrifugation of a cell lysate obtained by treating cells with detergents under controlled conditions. These studies introduced the biological concept that Golgi apparatus is capable to sort proteins and to send them to the plasma membrane through “rafts”, membrane lipid domains highly enriched in glycosphingolipids, sphingomyelin, ceramide and cholesterol. This concept has evolved and has been expanded in the last 10 years, and now several experimental approaches with the potential for observing these domains in intact cells are available. Here we critically discuss the necessity of discriminate between what is present on a cell membrane and what we can prepare from cell membranes in a laboratory tube
Gangliosides as Regulators of cell Membrane Organization and Functions
No full textGangliosides, characteristic complex lipids present in the external layer of plasma membranes, deeply influence the organization of the membrane as a whole and the function of specific membrane associated proteins due to lipid-lipid and lipid-protein lateral interaction. Here we discuss the basis for the membrane-organizing potential of gangliosides, examples of ganglioside-regulated membrane protein complexes and the mechanisms for the regulation of ganglioside membrane composition
Sphingolipids and membrane environments for caveolin
No full textAbstractCaveolin-1, and probably also -2 and -3, can organize multimolecular membrane complexes involved in transmembrane traffic, cell adhesion and signal transduction. In this review, we discuss on the importance of caveolin membrane environment in regulating the architecture and function of such complexes, with a special emphasis on the role of sphingolipids
Lipids and membrane lateral organization
Full text linkShortly after the elucidation of the very basic structure and properties of cellular membranes, it became evident that cellular membranes are highly organized structures with multiple and multi-dimensional levels of order. Very early observations suggested that the lipid components of biological membranes might be active players in the creations of these levels of order. In the late 80’s, several different and diverse experimental pieces of evidence coalesced together giving rise to the lipid raft hypothesis. Lipid rafts became enormously (and, in the opinion of these authors, sometimes acritically) popular, surprisingly not just within the lipidologist community (who is supposed to be naturally sensitive to the fascination of lipid rafts). Today, a PubMed search using the key word lipid rafts returned a list of 3767 papers, including 690 reviews (as a term of comparison, searching over the same time span for a very hot lipid-related key word, ceramide returned 6187 hits with 799 reviews), and a tremendous number of different cellular functions have been described as lipid raft-dependent. However, a clear consensus definition of lipid raft has been proposed only in recent times, and the basic properties, the ruling forces, and even the existence of lipid rafts in living cells have been recently matter of intense debate. The scenario that is gradually emerging from the controversies elicited by the lipid raft hypothesis emphasize multiple roles for membrane lipids in determining membrane order, that encompasses their tendency to phase separation but are clearly not limited to this. In this review, we would like to re-focus the attention of the readers on the importance of lipids in organizing the fine structure of cellular membranes
Dynamic and structural properties of Sphingolipids as driving forces for the formation of membrane domains
No full textA review on some features of membrane sphingolipids that should be involved in the generation of lipid domains. It discusses the primary role of the peculiar chemico-phys. features of this class of lipids as a driving force in detg. the properties of lipid membrane domains
Secondary accumulations of gangliosides in sphingolipidosis
No full textSphingolipid metabolism is deeply deregulated in several
pathologies. This seems to be responsible of neurodegeneration,
in sphingolipidosis. Here, we focus the attention on secondary
alterations of sphingolipid metabolism that have been sporadically
reported in the literature, in some sphingolipidosis.
We present a detailed analysis of the lipid composition in
different tissues from the acid sphingomyelinase-deficient mouse
(ASMKO), the animal model for Niemann-Pick disease type A,
characterized by the accumulation of sphingomyelin (SM). The
animal model of NPD type A, was developed using gene targeting
and embryo transfer techniques.
Results show, together with a general accumulation of SM, an
unexpected tissue specific selection of the accumulated molecular
species of SM, and of GM3 and GM2 gangliosides, that cannot be
solely explained by the lack of sphingomyelinase. We observed the
preferential accumulation of SM molecular species with shorter acyl
chains in the nervous system, but not in extraneural tissues. The
unbalance toward C18/C16-fatty acid containing SM species was
detectable as early as SM accumulation started, and monosialoganglioside
accumulation followed immediately afterwards. These
changes in sphingolipid patterns should thus represent the effect
of secondary biochemical pathways altered as a consequence of a
non-related primary cause. The mechanism underlying these
changes still remains to be elucidated and is probably the result
of changes in the expression and/or activity of more than one single
enzyme, and/or of anomalies in the traffic of the substrate/product
concentrations in multiple cellular compartments. Several pieces of
evidence suggest that altered sphingolipid metabolism results in a
non-physiological plasma membrane composition and organization,
leading to altered plasma membrane-originated signalling pathways
that could be relevant to the onset of cellular damage and of tissue
pathology
Glycosphingolipid behaviour in complex membranes
No full textAbstractGlycosphingolipids, due to their tendency to form laterally separated liquid-ordered phases, possess a high potential for the creation of order in biological membranes. The formation of glycosphingolipid-rich domains within the membrane has profound consequences on the membrane organization at different levels, and on the conformational and biological properties of membrane-associated proteins and multimolecular protein complexes. In this review, we will discuss 1) how glycosphingolipids influence the lateral organization of biological membranes; 2) how glycosphingolipids influence the function of membrane-associated proteins
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