Membrane lipids as signaling molecules.
ABSTRACT Membrane lipids play important roles in signaling reactions. They are involved in most if not all cellular signaling cascades and in a wide variety of tissue and cell types. The purpose of this review is to highlight major pathways of signaling originating in membrane lipids. Details of lipid metabolism, and its relation to protein function, will thus advance understanding of the role of lipids in health and disease.
Major classes of lipids including glycerophospholipids, their metabolites (eicosanoids, endocannabinoids), and sphingolipids have recently generated interest in the field of signal transduction. These lipids are tightly regulated and have an impact on various physiological functions. Importantly, aberrant lipid metabolism often leads to onset of pathology, and thus the precise balance of signaling lipids and their effectors can serve as biomarkers.
Membrane lipids form precursors for second messengers and functional assembly matrices on membrane domains during cellular stimulation. Many of these modifications are rapid reactions at lipid headgroups. Metabolism of the fatty acyl portion of membrane lipids leads to the generation of a bewildering complexity of lipid mediators with extended effects in space and time.
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ABSTRACT: Members of the P4 subfamily of P-type ATPases are thought to create and maintain lipid asymmetry in biological membranes by flipping specific lipids between membrane leaflets. In Arabidopsis, 7 of the 12 Aminophospholipid ATPase (ALA) family members are expressed in pollen. Here we show that double knockout of ALA6 and ALA7 (ala6/7) results in siliques with a ~2-fold reduction in seed set with a high frequency of empty seed positions near the bottom. Seed set was reduced to near zero when plants were grown under a hot/cold temperature stress. Reciprocal crosses indicate that the ala6/7 reproductive deficiencies are due to a defect related to pollen transmission. In-vitro growth assays provide evidence that ala6/7 pollen tubes are short and slow, with ~2-fold reductions in both maximal growth rate and overall length relative to wild-type. Outcrosses show that when ala6/7 pollen are in competition with wild-type pollen, they have a near 0% success rate in fertilizing ovules near the bottom of the pistil, consistent with ala6/7 pollen having short and slow growth defects. The ala6/7 phenotypes were rescued by the expression of either an ALA6-YFP or GFP-ALA6 fusion protein, which showed localization to both the plasma membrane and highly-mobile endomembrane structures. A mass spectrometry analysis of mature pollen grains revealed significant differences between ala6/7 and wild-type, both in the relative abundance of lipid classes and in the average number of double bonds present in acyl side chains. A change in the properties of the ala6/7 plasma membrane was also indicated by a ~10-fold reduction of labeling by lipophilic FM-dyes relative to wild-type. Together, these results indicate that ALA6 and ALA7 provide redundant activities that function to directly or indirectly change the distribution and abundance of lipids in pollen, and support a model in which ALA6 and ALA7 are critical for pollen fitness under normal and temperature-stress conditions.Frontiers in Plant Science 04/2015; 6:197. DOI:10.3389/fpls.2015.00197 · 3.64 Impact Factor
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ABSTRACT: El Texto ha sido pensado como un libro introductorio al análisis de lípidos de biomembranas para estudiantes de posgrado de Biología, Bioquímica, Biología Molecular y otros carreras afines. En el mismo se ha priorizado el desarrollo experimental de la metodología analítica de lípidos de biomembranas En cada etapa del análisis se presenta una breve introducción para luego desarrollar un método seleccionado por los autores, en cada capítulo se incluye un experimento con sus resultados esperados obtenidos de experimentos realizados por estudiantes del curso. Se agregaron además notas adicionales con algunas técnicas y datos útiles para el analista. Se han seleccionado técnicas simples y económicas que bastan para obtener información suficiente sobre la membrana del eritrocito y otros tejidos y membranas de origen natural. Se ha seleccionado como técnica separativa la cromatografía en capa fina que permite visualizar resultados con una inversión en equipamiento muy económica.Edited by Joaquin V Rodriguez Editor Científico, 11/2008; UNR EDitora., ISBN: ISBN: 978-950-673-663-7