Rab14 Regulates Apical Targeting in Polarized Epithelial Cells

Abstract

†These authors contributed equally to this work.Epithelial cells display distinct apical and basolateral membrane domains, and maintenance of this asymmetry is essential to the function of epithelial tissues. Polarized delivery of apical and basolateral membrane proteins from the trans Golgi network (TGN) and/or endosomes to the correct domain requires specific cytoplasmic machinery to control the sorting, budding and fission of vesicles. However, the molecular machinery that regulates polarized delivery of apical proteins remains poorly understood. In this study, we show that the small guanosine triphosphatase Rab14 is involved in the apical targeting pathway. Using yeast two-hybrid analysis and glutathione S-transferase pull down, we show that Rab14 interacts with apical membrane proteins and localizes to the TGN and apical endosomes. Overexpression of the GDP mutant form of Rab14 (S25N) induces an enlargement of the TGN and vesicle accumulation around Golgi membranes. Moreover, expression of Rab14-S25N results in mislocalization of the apical raft-associated protein vasoactive intestinal peptide/MAL to the basolateral domain but does not disrupt basolateral targeting or recycling. These data suggest that Rab14 specifically regulates delivery of cargo from the TGN to the apical domain.

Matrix vesicles: Are they anchored exosomes?

“…[12] This family of proteins regulate a wide range of activities that include vesicle formation and fusion to cognate membrane. [38, 39] The SNARE protein (Soluble NSF Attachment Protein REceptor)α is also present in these vesicles together with an ATPase N-ethylmaleimide-sensitive fusion (NSF) attachment protein receptor. The latter protein may drive the fusion of many of the endosomal membrane-trafficking events.…”

Apical trafficking in epithelial cells: signals, clusters and motors

“…Rab13 is involved in apical trafficking through its involvement in transport between the TGN and CRE (Nokes et al, 2008). Rab14 has been postulated to act in the transport of influenza hemagglutin (HA) to the apical surface (Kitt et al, 2008). Apical and basolateral endocytosis presumably depend on the same Rab proteins that have been studied in non-polarized cells, e.g.…”

Regulation of podocalyxin trafficking by Rab small GTPases in epithelial cells

“…17 In our recent study, the only Rab whose knockdown impaired the primary endocytic event and caused actual retention of PCX near the basal membrane in freshly attached cells was Rab14. 7 Actually, Rab14 has been reported to regulate apical targeting in MDCK cells and to be involved in early endocytic events, 18,19 although the exact mechanism of its action is yet to be elucidated.…”