Regulation of membrane trafficking in polarized epithelial cells

Fölsch, Heike

doi:10.1016/j.ceb.2008.01.003

Cited by 70 publications

(69 citation statements)

References 62 publications

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“…At the cellular level, we found that AP-1 is necessary for the polarised apical localisation of the oligopeptide transporter PEPT-1 and of the essential polarity proteins PAR-6 and CDC-42, as well as for the basolateral distribution of the monocarboxylate transporter SLCF-1. Apical and basolateral sorting in epithelial cells is a complex process and basolateral targeting has been extensively studied (Carmosino et al, 2009;Duffield et al, 2008;Folsch, 2008;Folsch et al, 2009;Gonzalez and RodriguezBoulan, 2009) whereas mechanisms underlying apical delivery have proven difficult to characterise (Golachowska et al, 2010;Weisz and Rodriguez-Boulan, 2009). Several hypotheses can be proposed for AP-1 function in apical trafficking.…”

Section: Discussionmentioning

confidence: 99%

AP-1 is required for the maintenance of apico-basal polarity in theC. elegansintestine

et al. 2012

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SUMMARYEpithelial tubes perform functions that are essential for the survival of multicellular organisms. Understanding how their polarised features are maintained is therefore crucial. By analysing the function of the clathrin adaptor AP-1 in the C. elegans intestine, we found that AP-1 is required for epithelial polarity maintenance. Depletion of AP-1 subunits does not affect epithelial polarity establishment or the formation of the intestinal lumen. However, the loss of AP-1 affects the polarised distribution of both apical and basolateral transmembrane proteins. Moreover, it triggers de novo formation of ectopic apical lumens between intestinal cells along the lateral membranes later during embryogenesis. We also found that AP-1 is specifically required for the apical localisation of the small GTPase CDC-42 and the polarity determinant PAR-6. Our results demonstrate that AP-1 controls an apical trafficking pathway required for the maintenance of epithelial polarity in vivo in a tubular epithelium.

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Section: Discussionmentioning

confidence: 99%

AP-1 is required for the maintenance of apico-basal polarity in theC. elegansintestine

et al. 2012

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“…The mechanism by which the presence of N-glycans can facilitate apical sorting of glycoproteins is poorly understood. The 1B-subunit of the AP-1B adaptor protein complex binds specifically to basolateral sorting motifs present in the cytoplasmic domains of basolateral proteins, promoting their placement into the basolateral transport containers and subsequent delivery to the basolateral membrane (25,26,28). It seems logical that a similar coupling between a sorting receptor and N-glycans would be used by the cell for delivery of glycoproteins to the apical membrane.…”

Section: Putative Apical Sorting Machinery That Recognizes N-glycansmentioning

confidence: 99%

Role of N-glycosylation in trafficking of apical membrane proteins in epithelia

Vagin

Kraut²,

Sachs³

2009

American Journal of Physiology-Renal Physiology

168

155

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ized distribution of plasma membrane transporters and receptors in epithelia is essential for vectorial functions of epithelia. This polarity is maintained by sorting of membrane proteins into apical or basolateral transport containers in the transGolgi network and/or endosomes followed by their delivery to the appropriate plasma membrane domains. Sorting depends on the recognition of sorting signals in proteins by specific sorting machinery. In the present review, we summarize experimental evidence for and against the hypothesis that N-glycans attached to the membrane proteins can act as apical sorting signals. Furthermore, we discuss the roles of N-glycans in the apical sorting event per se and their contribution to folding and quality control of glycoproteins in the endoplasmic reticulum or retention of glycoproteins in the plasma membrane. Finally, we review existing hypotheses on the mechanism of apical sorting and discuss the potential roles of the lectins, VIP36 and galectin-3, as putative apical sorting receptors. apical sorting; apical membrane retention; H-K-ATPase ␤-subunit; lectin EPITHELIAL CELLS CARRY OUT vectorial transport that requires polarized distribution of transporters and receptors to apical or basolateral membrane domains. These domains are separated by tight junctions that connect neighboring cells in the epithelial monolayer and act as diffusion barriers to prevent mixing of apical and basolateral membrane components (22). Asymmetric distribution of plasma membrane proteins is accomplished by their sorting into apical and basolateral containers in the trans-Golgi network (TGN) and/or endosomes followed by vectorial transport of these containers and insertion and retention of the proteins in the appropriate plasma membrane domains. Sorting depends on recognition of apical and basolateral sorting signals within the proteins by cellular sorting machinery (20,58,59,75,76).Numerous studies have indicated that both O-and N-glycans attached to the extracellular domains of some membrane proteins are important for apical location of these proteins. This review will focus on the role of N-glycans in polarized distribution of plasma membrane proteins in epithelia. The role of O-glycans in apical sorting has been described in several recent excellent reviews (18, 71) and will not be discussed further here.A putative role of N-glycans as apical sorting signals was postulated more than 10 years ago (24, 31). However, this hypothesis remains controversial primarily because N-glycans are important for the processes that precede or follow the actual sorting event, such as protein folding, quality control, endoplasmic reticulum (ER)-associated degradation, ER-to-Golgi trafficking, and retention of glycoproteins in the apical membrane. Therefore, merely examining the effect of altering the number or the nature of N-linked glycans on the relative abundance of the glycoprotein in the apical membrane, as has been done in many of the studies reported, does not allow one to distinguish between effects on apica...

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“…These functions require the maintenance of epithelial structural integrity through cell -cell and cell -extracellular matrix adhesion, and polarized targeting of transport and channel proteins to functionally di erent apical and basolateral plasma membrane domains. 1 Polarized targeting of proteins is regulated by di erential sorting and tra cking in the exocytic and endocytic pathways. 2 Little is known about how the cellular machineries involved in polarized sorting, tra cking, and delivering membrane proteins are regulated.…”

Section: The Epithelial Barriermentioning

confidence: 99%