Article

Alix regulates cortical actin and the spatial distribution of endosomes.

Department of Biochemistry, the Norwegian Radium Hospital, Montebello, Oslo.
Journal of Cell Science (impact factor: 6.11). 07/2005; 118(Pt 12):2625-35. DOI:10.1242/jcs.02382
Source: PubMed

ABSTRACT Alix/AIP1 is a proline-rich protein that has been implicated in apoptosis, endocytic membrane trafficking and viral budding. To further elucidate the functions of Alix, we used RNA interference to specifically suppress its expression. Depletion of Alix caused a striking redistribution of early endosomes from a peripheral to a perinuclear location. The redistribution of endosomes did not affect transferrin recycling or degradation of endocytosed epidermal growth factor receptors, although the uptake of transferrin was mildly reduced when Alix was downregulated. Quantitative immunoelectron microscopy showed that multivesicular endosomes of Alix-depleted cells contained normal amounts of CD63, whereas their levels of lysobisphosphatidic acid were reduced. Alix depletion also caused an accumulation of unusual actin structures that contained clathrin and cortactin, a protein that couples membrane dynamics to the cortical actin cytoskeleton. Our results suggest that Alix functions in the actin-dependent intracellular positioning of endosomes, but that it is not essential for endocytic recycling or for trafficking of membrane proteins between early and late endosomes in non-polarised cells.

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Keywords

actin-dependent intracellular positioning
 
Alix
 
Alix depletion
 
Alix functions
 
Alix-depleted cells
 
contained clathrin
 
cortical actin cytoskeleton
 
couples membrane dynamics
 
endocytic membrane trafficking
 
endocytic recycling
 
endocytosed epidermal growth factor receptors
 
functions
 
lysobisphosphatidic acid
 
non-polarised cells
 
peripheral
 
Quantitative immunoelectron microscopy
 
RNA interference
 
striking redistribution
 
trafficking
 
transferrin recycling