title: The exocyst complex regulates free fatty acid uptake by adipocytes.
abstract: The exocyst is an octameric molecular complex that drives vesicle trafficking in adipocytes, a rate-limiting step in insulin-dependent glucose uptake. This study assessed the role of the exocyst complex in regulating free fatty acid (FFA) uptake by adipocytes. Upon differentiating into adipocytes, 3T3-L1 cells acquire the ability to incorporate extracellular FFAs in an insulin-dependent manner. A kinetic assay using fluoresceinated FFA (C12 dodecanoic acid) uptake allows the real-time monitoring of FFA internalization by adipocytes. The insulin-dependent uptake of C12 dodecanoic acid by 3T3-L1 adipocytes is mediated by Akt and phosphatidylinositol 3 (PI3)-kinase. Gene silencing of the exocyst components Exo70 and Sec8 significantly reduced insulin-dependent FFA uptake by adipocytes. Consistent with the roles played by Exo70 and Sec8 in FFA uptake, mCherry-tagged Exo70 and HA-tagged Sec8 partially colocalize with lipid droplets within adipocytes, suggesting their active roles in the development of lipid droplets. Tubulin polymerization was also found to regulate FFA uptake in collaboration with the exocyst complex. This study demonstrates a novel role played by the exocyst complex in the regulation of FFA uptake by adipocytes.
authors.affiliation: Division of Metabolism, Endocrinology & Diabetes (MEND), Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, United States of America.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Division of Metabolism, Endocrinology & Diabetes (MEND), Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, United States of America; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States of America.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Akama
authors.affiliation: Division of Metabolism, Endocrinology & Diabetes (MEND), Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, United States of America; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States of America.
authors.forename: Yibin
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Division of Metabolism, Endocrinology & Diabetes (MEND), Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, United States of America; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States of America.
authors.forename: Tae-Hwa
authors.initials: TH
authors.lastname: Chun
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D020868:Gene Silencing; D007700:Kinetics; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D034622:RNA Interference; D014404:Tubulin / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics
chemical_list: D002352:Carrier Proteins; C522783:Exo70 protein, mouse; D005230:Fatty Acids, Nonesterified; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C489608:Sec8l1 protein, mouse; D014404:Tubulin; D033921:Vesicular Transport Proteins; D058539:Phosphatidylinositol 3-Kinase