INVESTIGADORES
VALDEZ Javier Esteban
artículos
Título:
Slow Diffusion of Proteins in the Yeast Plasma Membrane Allows Polarity to Be Maintained by Endocytic Cycling
Autor/es:
VALDEZ TAUBAS J; PELHAM HR
Revista:
CURRENT BIOLOGY
Editorial:
CELL PRESS
Referencias:
Año: 2003 vol. 13 p. 1636 - 1640
ISSN:
0960-9822
Resumen:
Yeast
cells and the mating intermediates termed schmoos show a polarised distribution
of some plasma membrane proteins.
Maintenance of this polarity is not well understood. Here we show that the exocytic SNARE Snc1,
which normally recycles between plasma membrane, endosomes and the Golgi, is
polarised on the surface of both normal cells and schmoos, and that this
requires its endocytosis. Endocytic
cycling, together with localised exocytosis, is sufficient to generate polarity
because the rate of diffusion of Snc1 and other proteins in the yeast plasma
membrane is very much slower than would be expected from measurements in animal
cells. Slow diffusion is a property of
the plasma membrane: it is not observed on vacuolar membranes, and does not
require the cell wall or polymerised actin, but is partially affected in an erg6 mutant defective in ergosterol
synthesis. An alternative model for
schmoo polarity has recently been proposed in which protein localisation is
driven by an asymmetric distribution of ergosterol-containing lipid rafts. We have reinvestigated this, and conclude
that neither the location of a GPI-linked marker protein nor filipin staining
provides evidence to support such a model.
In contrast, endocytic cycling provides a simple and flexible mechanism
for polarity maintenance.