The Rab8 GTPase selectively regulates AP-1B-dependent basolateral transport in polarized Madin-Darby canine kidney cells.
The AP-1B clathrin adaptor complex plays a key role in the recognition and intracellular transport of many membrane proteins destined for the basolateral surface of epithelial cells. However, little is known about other components that act in conjunction with AP-1B. We found that the Rab8 GTPase is one such component. Expression of a constitutively activated GTP hydrolysis mutant selectively inhibited basolateral (but not apical) transport of newly synthesized membrane proteins. Moreover, the effects were limited to AP-1B-dependent basolateral cargo; basolateral transport of proteins containing dileucine targeting motifs that do not interact with AP-1B were targeted normally despite overexpression of mutant Rab8. Similar results were obtained for a dominant-negative allele of the Rho GTPase Cdc42, previously implicated in basolateral transport but now shown to be selective for the AP-1B pathway. Rab8-GFP was localized to membranes in the TGN-recycling endosome, together with AP-1B complexes and the closely related but ubiquitously expressed AP-1A complex. However, expression of active Rab8 caused a selective dissociation of AP-1B complexes, reflecting the specificity of Rab8 for AP-1B-dependent transport.
Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, CT 06520-8002, USA.
Agnes Lee
AL
Ang
Heike
H
Fölsch
Ulla-Maija
UM
Koivisto
Marc
M
Pypaert
Ira
I
Mellman
D033961:Adaptor Protein Complex 1 / Q000378:metabolism; D033982:Adaptor Protein Complex gamma Subunits / Q000378:metabolism; D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D015415:Biomarkers; D002460:Cell Line; D016764:Cell Polarity / Q000502:physiology*; D004285:Dogs; D011992:Endosomes / Q000378:metabolism; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism* / Q000648:ultrastructure; D015870:Gene Expression; D007668:Kidney / Q000166:cytology*; D009154:Mutation; D014168:Transferrin / Q000493:pharmacokinetics; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D021601:trans-Golgi Network / Q000378:metabolism / Q000648:ultrastructure
D033961:Adaptor Protein Complex 1; D033982:Adaptor Protein Complex gamma Subunits; D015415:Biomarkers; D014168:Transferrin; D020558:GTP Phosphohydrolases; D020764:cdc42 GTP-Binding Protein; D020691:rab GTP-Binding Proteins