Phospholipid diversity: Correlation with membrane-membrane fusion events |
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Authors: | F Deeba K Sharma Sharad S Akhtar O Mohammad |
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Institution: | a Inter-disciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, 202002 India b Faculty of Pharmacy, Jamia Hamdard, New Delhi-62, India |
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Abstract: | The transport of various metabolically important substances along the endocytic and secretory pathways involves budding as well as fusion of vesicles with various intracellular compartments and plasma membrane. The membrane-membrane fusion events between various sub-compartments of the cell are believed to be mainly mediated by so-called “fusion proteins”. This study shows that beside the proteins, lipid components of membrane may play an equally important role in fusion and budding processes. Inside out (ISO) as well as right side out (RSO) erythrocyte vesicles were evaluated for their fusogenic potential using conventional membrane fusion assay methods. Both fluorescence dequenching as well as content mixing assays revealed fusogenic potential of the erythrocyte vesicles. Among two types of vesicles, ISO were found to be more fusogenic as compared to the RSO vesicles. Interestingly, ISO retained nearly half of their fusogenic properties after removal of the proteins, suggesting the remarkable role of lipids in the fusion process. In another set of experiments, fusogenic properties of the liposomes (subtilosome), prepared from phospholipids isolated from Bacillus subtilis (a lower microbe) were compared with those of erythrocyte vesicles. We have also demonstrated that various types of vesicles upon interaction with macrophages deliver encapsulated materials to the cytosol of the cells. Membrane-membrane fusion was also followed by the study, in which a protein synthesis inhibitor ricin A (that does not cross plasma membrane), when encapsulated in the erythrocyte vesicles or subtilosomes was demonstrated to gain access to the cytosol. |
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Keywords: | ISO Inside out vesicles RSO Right side out vesicles LUV Large unilamellar vesicles EL Erythrocyte lipids OVA Ovalbumin PC Phosphatidylcholine PS Phosphatidylserine PE Phosphatidylethanolamine R18 Octadecylrhodamine B-chloride NBD-PE l-(Phosphatidylethanolamine-N-(4-nitrobenzo-2-oxa-1" target="_blank">l-(Phosphatidylethanolamine-N-(4-nitrobenzo-2-oxa-1 3-diazole) Rh-PE N-(Lissamine rhodamine B sulfonyl)phosphatidylethanolamine ANTS l-Aminonapthalene-3" target="_blank">l-Aminonapthalene-3 6 8-trisulfonic acid DPX N N'-p-Xylylenebis (pyridinium bromide) DMEM Dulbecco's modified Eagle medium HBSS Hanks balanced salt solution FCS Fetal calf serum CTL Cytotoxic T lymphocyte |
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