Scrambling of natural and fluorescently tagged phosphatidylinositol by reconstituted G protein-coupled receptor and TMEM16 scramblases
| Autor: | Peter Bütikofer, Anant K. Menon, Kiran K. Andra, Lei Wang, Kalpana Pandey, Yugo Iwasaki |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Phospholipid scramblase Phospholipid Anoctamins Phosphatidylinositols Biochemistry Fluorescence Fungal Proteins 03 medical and health sciences chemistry.chemical_compound Animals Phospholipid Transfer Proteins 610 Medicine & health Molecular Biology G protein-coupled receptor Liposome Nectria Opsins 030102 biochemistry & molecular biology Phospholipase C Chemistry Hydrolysis Endoplasmic reticulum Vesicle Biological Transport Cell Biology Lipids Transmembrane protein Kinetics 030104 developmental biology Type C Phospholipases 570 Life sciences biology Cattle lipids (amino acids peptides and proteins) |
| DOI: | 10.7892/boris.124498 |
| Popis: | Members of the G protein–coupled receptor and TMEM16 (transmembrane protein 16) protein families are phospholipid scramblases that facilitate rapid, bidirectional movement of phospholipids across a membrane bilayer in an ATP-independent manner. On reconstitution into large unilamellar vesicles, these proteins scramble more than 10,000 lipids/protein/s as measured with co-reconstituted fluorescent nitrobenzoxadiazole (NBD)-labeled phospholipids. Although NBD-labeled phospholipids are ubiquitously used as reporters of scramblase activity, it remains unclear whether the NBD modification influences the quantitative outcomes of the scramblase assay. We now report a refined biochemical approach for measuring the activity of scramblase proteins with radiolabeled natural phosphatidylinositol ([(3)H]PI) and exploiting the hydrolytic activity of bacterial PI-specific phospholipase C (PI-PLC) to detect the transbilayer movement of PI. PI-PLC rapidly hydrolyzed 50% of [(3)H]PI in large symmetric, unilamellar liposomes, corresponding to the lipid pool in the outer leaflet. On reconstitution of a crude preparation of yeast endoplasmic reticulum scramblase, purified bovine opsin, or purified Nectria haematococca TMEM16, the extent of [(3)H]PI hydrolysis increased, indicating that [(3)H]PI from the inner leaflet had been scrambled to the outer leaflet. Using transphosphatidylation, we synthesized acyl-NBD-PI and used it to compare our PI-PLC–based assay with conventional fluorescence-based methods. Our results revealed quantitative differences between the two assays that we attribute to the specific features of the assays themselves rather than to the nature of the phospholipid. In summary, we have developed an assay that measures scrambling of a chemically unmodified phospholipid by a reconstituted scramblase. |
| Databáze: | OpenAIRE |
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