Protein-mediated fusion of liposomes with microsomal membranes of XXXX : evidence for a complex mechanism dealing with membranous and cytosolic fusogenic proteins.

@entity969 @entity3456 @entity11150 @entity165
Membrane fusion is a fundamental and wide-spread phenomenon in the functioning of cells. Many studies were carried out concerning fusion of plasma membranes as for example cell-cell fusions or uptake by cells of lipid-enveloped viruses. The present study deals with the interaction of intracellular membranes of @entity11150 with artificial membranes (liposomes). Association is monitored by the uptake of radioactive liposomes by fungal microsomal membranes. The discrimination between aggregation and pure fusion is done by layering the liposomes-microsomes mixture on a continuous @entity969 gradient. The accurate quantitation of the fusion phenomenon is monitored with a fluorescent assay based on resonance energy transfer (Struck, D.K. et al. (1981) Biochemistry 20, 4093-4099). Both methods show that, at physiological pH, there is a spontaneous fusion of microsomes with @entity165 -free liposomes. This phenomenon is protein dependent as trypsinized microsomal membranes are no longer able to fuse with liposomes. Biological significance of the fusion process has been demonstrated using microsomal intrinsic protein mannosylation assay; the enhancement of the lipid to protein ratio due to the fusion of liposomes with microsomes of A. @entity3456 results in an increase in the rate of endogenous proteins mannosylation. Moreover, cytosolic proteins of A. @entity3456 promote the fusion of any kind of liposomes with microsomes.
