A dual role of the N-terminal FQQI motif in GLUT4 trafficking.
In adipocytes, the glucose transporter GLUT4 recycles between intracellular storage vesicles and the plasma membrane. GLUT4 is internalized by a clathrin- and dynamin-dependent mechanism, and sorted into an insulin-sensitive storage compartment. Insulin stimulation leads to GLUT4 accumulation on the cell surface. The N-terminal F5QQI motif in GLUT4 has been shown previously to be required for sorting of the protein in the basal state. Here, we show that the FQQI motif is a binding site for the medium chain adaptin micro1, a subunit of the AP-1 adaptor complex that plays a role in post-Golgi/endosomal trafficking events. In order to investigate the role of AP-1 and AP-2 in GLUT4 trafficking, we generated 3T3-L1 adipocytes expressing HA-GLUT4-GFP and knocked down the AP-1 and AP-2 complex by RNAi, respectively. In AP-1 and AP-2 knockdown adipocytes, GLUT4 accumulates at the cell surface in the basal state, consistent with a role of AP-1 in post-endosomal sorting of GLUT4 to the insulin-sensitive storage compartment, and of AP-2 in clathrin-mediated endocytosis. Our data demonstrate a dual role of the F5QQI motif and support the conclusion that the AP complexes direct GLUT4 trafficking and endocytosis.
Bernhardt
Ulrike
U
Department of Pharmacology, German Institute of Human Nutrition (Potsdam-Rehbrücke), Nuthetal, Germany. ulrike.bernhardt@charite.de
Carlotti
Françoise
F
Hoeben
Rob C
RC
Joost
Hans-Georg
HG
Al-Hasani
Hadi
H
D041721:3T3-L1 Cells; D020816:Amino Acid Motifs / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D011992:Endosomes / Q000378:metabolism; D005822:Genetic Vectors / Q000235:genetics; D051275:Glucose Transporter Type 4 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D034741:RNA, Small Interfering; D016415:Sequence Alignment; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D050656:Transcription Factor AP-2 / Q000235:genetics / Q000378:metabolism / Q000502:physiology
D051275:Glucose Transporter Type 4; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1; D050656:Transcription Factor AP-2