抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

A new aspect of cell membrane structure is presented, based on the dynamic clustering of sphingolipids and cholesterol to form rafts that move within the fluid bilayer. It is proposed that these rafts function as platforms for the attachment of proteins when membranes are moved around inside the cell and during signal transduction.

Functional rafts in cell membranes

Cell signaling by receptor-tyrosine kinases

Signal transduction is initiated by complex protein-protein interactions between ligands, receptors and kinases, to name only a few. It is now becoming clear that lipid micro-environments on the cell surface -- known as lipid rafts -- also take part in this process. Lipid rafts containing a given set of proteins can change their size and composition in response to intra- or extracellular stimuli. This favours specific protein-protein interactions, resulting in the activation of signalling cascades.

/pdf/lipid-rafts-and-signal-transduction-2pg659jt8g.pdf

Lipid rafts and signal transduction

http://www.ipg.org.br/Rosa_Rademakers_Neuron%20tese%20integra.pdf

Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS

Publisher Summary Polarized exocytic transport in epithelial cells can be measured by performing in vitro assays on filter-grown Madin–Darby canine kidney cells. The transport is assayed either early in the biosynthetic pathway, from the endoplasmic reticulum (ER) to the Golgi complex, or from the trans-Golgi network (TGN) to the apical or from the TGN to the basolateral plasma membrane. Membrane-impermeable molecules can gain access to lipids or membrane proteins facing the cytosol. Each batch of toxin is standardized for the amount of lactate dehydrogenase (LDH) released from the filter-grown MDCK cells, and the amount of LDH released is determined according to a previously described protocol. Measure the protein concentration, which should be around 5 mg/ml. Lower concentrations do not work. When needed, thaw the aliquots quickly and keep them on ice (up to 6 h) until use. Aliquots can be refrozen at least twice. Due to the handling and the various steps, the entire procedure for running one assay requires about 9 h for the apical assay and 11 h for the basolateral assay.

Permeabilized Epithelial Cells to Study Exocytic Membrane Transport

Introduction: new aspects of cellular sterol metabolism and transport.

&lt;div&gt;Abstract&lt;p&gt;Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest malignancies and potentially curable only with radical surgical resection at early stages. The tumor microenvironment has been shown to be central to the development and progression of PDAC. A better understanding of how early human PDAC metabolically communicates with its environment and differs from healthy pancreas could help improve PDAC diagnosis and treatment. Here we performed deep proteomic analyses from diagnostic specimens of operable, treatment-naïve PDAC patients (&lt;i&gt;n&lt;/i&gt; = 14), isolating four tissue compartments by laser-capture microdissection: PDAC lesions, tumor-adjacent but morphologically benign exocrine glands, and connective tissues neighboring each of these compartments. Protein and pathway levels were compared between compartments and with control pancreatic proteomes. Selected targets were studied immunohistochemically in the 14 patients and in additional tumor microarrays, and lipid deposition was assessed by nonlinear label-free imaging (&lt;i&gt;n&lt;/i&gt; = 16). Widespread downregulation of pancreatic secretory functions was observed, which was paralleled by high cholesterol biosynthetic activity without prominent lipid storage in the neoplastic cells. Stromal compartments harbored ample blood apolipoproteins, indicating abundant microvasculature at the time of tumor removal. The features best differentiating the tumor-adjacent exocrine tissue from healthy control pancreas were defined by upregulation of proteins related to lipid transport. Importantly, histologically benign exocrine regions harbored the most significant prognostic pathways, with proteins involved in lipid transport and metabolism, such as neutral cholesteryl ester hydrolase 1, associating with shorter survival. In conclusion, this study reveals prognostic molecular changes in the exocrine tissue neighboring pancreatic cancer and identifies enhanced lipid transport and metabolism as its defining features.&lt;/p&gt;Significance:&lt;p&gt;In clinically operable pancreatic cancer, regions distant from malignant cells already display proteomic changes related to lipid transport and metabolism that affect prognosis and may be pharmacologically targeted.&lt;/p&gt;&lt;/div&gt; 

Data from Lipid Metabolic Reprogramming Extends beyond Histologic Tumor Demarcations in Operable Human Pancreatic Cancer

DOI:10.1097/MOL.0000000000000201 Intracellular lipid transport processes are fundamental to cellular homeostasis, but elucidation of the underlying mechanisms has been challenging. Lipid researchers are now turning to systematic ‘omics’based strategies to tackle these issues. Chu et al. [1 && ] developed a clever genome-wide shRNA screen specifically focusing on lysosomal cholesterol exit. Surprisingly, peroxisomal proteins were significantly enriched in this screen. The authors then provide evidence that peroxisomes transiently interacted with lysosomes depending on the incoming cholesterol load. These contacts as well as cholesterol transport were facilitated by phosphatidylinositol(4,5)P2-dependent binding of synaptotagmin 7 that bridges lysosomes to peroxisomes. On the basis of filipin staining, fibroblasts from human patients and adrenal gland as well as brain tissue from mice with peroxisomal disorders displayed cholesterol accumulation in the late endosomal/lysosomal system. Peroxisomal disorders are primarily characterized by the accumulation of very long chain fatty acids [2]. Interestingly, peroxisomes have also been implicated in cholesterol and bile acid synthesis [3], and there are data that cholesterol balance is altered in peroxisomal disorders. Curiously, cholesterol levels have been reported to be either unaffected or decreased in peroxisome biogenesis defective human fibroblasts, mouse liver or serum [3,4], which is not easy to reconcile with the findings of Chu et al.. It might be that peroxisomal dysfunction results in subcellular cholesterol redistribution without a net increase in cholesterol content. Alternatively, as several different gene defects can lead to peroxisomal disorders, this might manifest in variable metabolic consequences, with some leading to more pronounced cholesterol alterations than others. Another recent, holistic perspective on intracellular lipid balance is provided by Casanovas et al. [5 && ]. They performed detailed proteomic and lipidomic analyses of the yeast Saccharomyces cerevisiae along its growth profile, from proliferative to stationary cell growth and from fermentation to respiration. Over 3000 proteins changed in abundance during these stages. The parallel monitoring of more than 200 lipid species enabled the authors

Lipid transport takes the 'omics' highway.

Objective: Identification of cellular defects underlying hypercholesterolemia in individual persons remains challenging. We aimed at establishing high-content assays for the quantitative assessment of lipid uptake and removal in accessible primary human cells to obtain new insights into the disease. Approach and Results: We set up a multiparametric imaging platform for the quantification of LDL uptake and lipid storage in cytoplasmic droplets of leukocyte populations from peripheral blood. The 39 individuals from the FINRISK2012 cohort and 23 heterozygous familial hypercholesterolemia (He-FH) patients from the METSIM cohort displayed variable LDL uptake, including patients carrying identical LDLR mutations. Moreover, He-FH patients that remained hypercholesterolemic despite statin treatment displayed low monocyte LDL uptake. In non-FH individuals, reduced LDL uptake correlated with higher body mass index (BMI) and larger hip circumference. Cellular lipid droplet quantifications enabled us to define a new parameter, lipid mobilization, describing the efficiency with which cells depleted their lipid reservoirs. Lipid mobilization correlated positively with LDL uptake and negatively with hypercholesterolemia and age, differentiating individuals with normal and elevated LDL-cholesterol (LDL-c) better than LDL uptake. Moreover, combination of cell-based readouts with a polygenic risk score for LDL-c explained hypercholesterolemia better than the genetic risk score alone. Conclusions: This study demonstrates how multiplexed cell-based assays, including novel quantifiable parameters for lipid removal, provide handles to dissect the hetereogeneity of defects contributing to hypercholesterolemia at the level of individuals.

/pdf/multiparametric-profiling-of-cellular-lipid-metabolism-in-3dl16exb9v.pdf

Elina Ikonen

Papers

Permeabilized Epithelial Cells to Study Exocytic Membrane Transport

Introduction: new aspects of cellular sterol metabolism and transport.

Data from Lipid Metabolic Reprogramming Extends beyond Histologic Tumor Demarcations in Operable Human Pancreatic Cancer

Lipid transport takes the 'omics' highway.

Multiparametric profiling of cellular lipid metabolism in hypercholesterolemia