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J Cell Biol. 2004 Nov 22;167(4):699-709.

Protein oligomerization modulates raft partitioning and apical sorting of GPI-anchored proteins.

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Dipartimento di Biologia e Patologia Cellulare e Molecolare, Centro di Endocrinologia ed Oncologia Sperimentale, CNR, Università degli Studi di Napoli Federico II, Italy.


An essential but insufficient step for apical sorting of glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) in epithelial cells is their association with detergent-resistant microdomains (DRMs) or rafts. In this paper, we show that in MDCK cells both apical and basolateral GPI-APs associate with DRMs during their biosynthesis. However, only apical and not basolateral GPI-APs are able to oligomerize into high molecular weight complexes. Protein oligomerization begins in the medial Golgi, concomitantly with DRM association, and is dependent on protein-protein interactions. Impairment of oligomerization leads to protein missorting. We propose that oligomerization stabilizes GPI-APs into rafts and that this additional step is required for apical sorting of GPI-APs. Two alternative apical sorting models are presented.

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