Biomaterial Database

Freeze-fracture analysis of the effects of intermediates of the phosphatidylinositol cycle on fusion of rough endoplasmic reticulum membranes. 1992

F W Kan, and M Jolicoeur, and J Paiement

Département d'anatomie, Faculté de médicine, Université de Montréal, Québec, Canada.

While searching for the identity of the effector of the putative GTP-binding protein involved in fusion of rough endoplasmic reticulum (RER) cell-free incubation conditions were found permitting fusion in a GTP-independent manner. Membrane fusion was obtained using medium required to study synthesis of phosphatidylinositol (PI). We now report on the effects of various co-factors and intermediates of the PI cycle on the interaction of rough microsomes. By freeze-fracture, fusion of rough microsomes was defined as the appearance of fracture-planes of membrane larger than those of unincubated membrane. Cytosine triphosphate (CTP, 3 mM) in the presence of 2 mM MnCl2 was most effective in stimulating fusion. Guanosine triphosphate (GTP) at the same concentration, could substitute for CTP to stimulate fusion, ATP, ITP, UTP and guanosine 5'-[gamma-thio]triphosphate (GTP gamma S) could not. When combined together in the same medium CTP potentiated the effect of GTP. Arachidonic acid (20 micrograms/ml) also stimulated fusion in the presence of MnCl2. This led to the appearance of large fracture-planes of membrane with a heterogeneous distribution of intramembranous particles. Other saturated fatty acids at the same concentration did not stimulate fusion. Phosphatidylinositol (PI, 50 micrograms) and 2 mM MnCl2 had a similar effect as arachidonic acid and MnCl2 in stimulating fusion. The PI effect was largely augmented in the presence of CTP. Our results are consistent with the concept that metabolism of phospholipids may modulate GTP-dependent fusion of RER membranes.

UI	MeSH Term	Description	Entries
D008560	Membrane Fluidity	The motion of phospholipid molecules within the lipid bilayer, dependent on the classes of phospholipids present, their fatty acid composition and degree of unsaturation of the acyl chains, the cholesterol concentration, and temperature.	Bilayer Fluidity,Bilayer Fluidities,Fluidities, Bilayer,Fluidities, Membrane,Fluidity, Bilayer,Fluidity, Membrane,Membrane Fluidities
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D008862	Microsomes, Liver	Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough.	Liver Microsomes,Liver Microsome,Microsome, Liver
D010716	Phosphatidylinositols	Derivatives of phosphatidic acids in which the phosphoric acid is bound in ester linkage to the hexahydroxy alcohol, myo-inositol. Complete hydrolysis yields 1 mole of glycerol, phosphoric acid, myo-inositol, and 2 moles of fatty acids.	Inositide Phospholipid,Inositol Phosphoglyceride,Inositol Phosphoglycerides,Inositol Phospholipid,Phosphoinositide,Phosphoinositides,PtdIns,Inositide Phospholipids,Inositol Phospholipids,Phosphatidyl Inositol,Phosphatidylinositol,Inositol, Phosphatidyl,Phosphoglyceride, Inositol,Phosphoglycerides, Inositol,Phospholipid, Inositide,Phospholipid, Inositol,Phospholipids, Inositide,Phospholipids, Inositol
D003570	Cytidine Triphosphate	Cytidine 5'-(tetrahydrogen triphosphate). A cytosine nucleotide containing three phosphate groups esterified to the sugar moiety.	CTP,CRPPP,Magnesium CTP,Mg CTP,Triphosphate, Cytidine
D004721	Endoplasmic Reticulum	A system of cisternae in the CYTOPLASM of many cells. In places the endoplasmic reticulum is continuous with the plasma membrane (CELL MEMBRANE) or outer membrane of the nuclear envelope. If the outer surfaces of the endoplasmic reticulum membranes are coated with ribosomes, the endoplasmic reticulum is said to be rough-surfaced (ENDOPLASMIC RETICULUM, ROUGH); otherwise it is said to be smooth-surfaced (ENDOPLASMIC RETICULUM, SMOOTH). (King & Stansfield, A Dictionary of Genetics, 4th ed)	Ergastoplasm,Reticulum, Endoplasmic
D005614	Freeze Fracturing	Preparation for electron microscopy of minute replicas of exposed surfaces of the cell which have been ruptured in the frozen state. The specimen is frozen, then cleaved under high vacuum at the same temperature. The exposed surface is shadowed with carbon and platinum and coated with carbon to obtain a carbon replica.	Fracturing, Freeze,Fracturings, Freeze,Freeze Fracturings
D006160	Guanosine Triphosphate	Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.	GTP,Triphosphate, Guanosine
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D051381	Rats	The common name for the genus Rattus.	Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus