title: The glucose transporter 4 FQQI motif is necessary for Akt substrate of 160-kilodalton-dependent plasma membrane translocation but not Golgi-localized (gamma)-ear-containing Arf-binding protein-dependent entry into the insulin-responsive storage compartment.
abstract: Newly synthesized glucose transporter 4 (GLUT4) enters into the insulin-responsive storage compartment in a process that is Golgi-localized gamma-ear-containing Arf-binding protein (GGA) dependent, whereas insulin-stimulated translocation is regulated by Akt substrate of 160 kDa (AS160). In the present study, using a variety of GLUT4/GLUT1 chimeras, we have analyzed the specific motifs of GLUT4 that are important for GGA and AS160 regulation of GLUT4 trafficking. Substitution of the amino terminus and the large intracellular loop of GLUT4 into GLUT1 (chimera 1-441) fully recapitulated the basal state retention, insulin-stimulated translocation, and GGA and AS160 sensitivity of wild-type GLUT4 (GLUT4-WT). GLUT4 point mutation (GLUT4-F5A) resulted in loss of GLUT4 intracellular retention in the basal state when coexpressed with both wild-type GGA and AS160. Nevertheless, similar to GLUT4-WT, the insulin-stimulated plasma membrane localization of GLUT4-F5A was significantly inhibited by coexpression of dominant-interfering GGA. In addition, coexpression with a dominant-interfering AS160 (AS160-4P) abolished insulin-stimulated GLUT4-WT but not GLUT4-F5A translocation. GLUT4 endocytosis and intracellular sequestration also required both the amino terminus and large cytoplasmic loop of GLUT4. Furthermore, both the FQQI and the SLL motifs participate in the initial endocytosis from the plasma membrane; however, once internalized, unlike the FQQI motif, the SLL motif is not responsible for intracellular recycling of GLUT4 back to the specialized compartment. Together, we have demonstrated that the FQQI motif within the amino terminus of GLUT4 is essential for GLUT4 endocytosis and AS160-dependent intracellular retention but not for the GGA-dependent sorting of GLUT4 into the insulin-responsive storage compartment.
authors.affiliation: Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794-8651, USA.
authors.forename: Encarnación
authors.initials: E
authors.lastname: Capilla
authors.forename: Naoko
authors.initials: N
authors.lastname: Suzuki
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Pessin
authors.forename: June Chunqiu
authors.initials: JC
authors.lastname: Hou
mesh_terms: D041721:3T3-L1 Cells; D020727:ADP-Ribosylation Factors / Q000378:metabolism; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D017667:Adipocytes / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D004705:Endocytosis; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D051275:Glucose Transporter Type 4 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C407306:GGA adaptor proteins; D020690:GTPase-Activating Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; C505647:Tbc1d4 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D020727:ADP-Ribosylation Factors