Artículo de revista
Lens Major Intrinsic Protein (MIP) Promotes Adhesion When Reconstituted into Large Unilamellar Liposomes
Fecha
1994Registro en:
Biochemistry, Vol. 33, No. 24, 1994, 7663-7669
Autor
Michea Acevedo, Luis
Fuente Vera, Milton de la
Lagos Wilson, Néstor
Institución
Resumen
The vertebrate lens behaves like a syncytium, and it is formed mainly by cells called lens fibers.
Between the fibers are extensive networks of membrane junctions. The major intrinsic protein (MIP)
constitutes about 50-60% of the intrinsic membrane proteins found in lens fiber junctions. The role of MIP
is unknown. Nevertheless, it has been proposed that it is the protein responsible for the adhesion between
the plasmatic membranes of the lens fibers. The aim of our studies was to test the adhesion-promoting role
of MIP. We reconstituted MIP into large unilamellar vesicles (LUV) of phosphatidylcholine (PC) and
studied the vesicle aggregation between MIP-reconstituted LUV (PC-MIP) and phosphatidylserine (PS)
vesicles. The aggregation process was monitored using methods based on resonance energy transfer (RET)
and turbidity measurements. Neither RET nor an increase in turbidity occurred in any combination except
in the presence of both MIP and PS. The liposomes thus aggregate through protein-lipid interactions.
These results show that MIP promotes adhesion with negatively charged membranes, indicating that the
adhesion is electrostatic in nature. Aggregation was fastest a t pH 6.0. The aggregation effect was abolished
with pronase treatment. Preincubation of PC-MIP vesicles with anti-MIP polyclonal serum also inhibited
the aggregation. These studies are the first experimental evidence supporting the hypothesis of an adhesive
role for MIP.