Knockout of syntaxin-4 in 3T3-L1 adipocytes reveals new insight into GLUT4 trafficking and adiponectin secretion

Hannah L. Black, Rachel Livingstone, Cynthia C. Mastick, Mohammed Al Tobi, Holly Taylor, Angéline Geiser, Laura Stirrat, Dimitrios Kioumourtzoglou, John R. Petrie, James G. Boyle, Nia J. Bryant, Gwyn W. Gould

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
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Abstract

Adipocytes are key to metabolic regulation, exhibiting insulin-stimulated glucose transport that is underpinned by the insulin-stimulated delivery of glucose transporter type 4 (SLC2A4, also known and hereafter referred to as GLUT4)-containing vesicles to the plasma membrane where they dock and fuse, and increase cell surface GLUT4 levels. Adipocytokines, such as adiponectin, are secreted via a similar mechanism. We used genome editing to knock out syntaxin-4, a protein reported to mediate fusion between GLUT4-containing vesicles and the plasma membrane in 3T3-L1 adipocytes. Syntaxin-4 knockout reduced insulin-stimulated glucose transport and adiponectin secretion by ∼50% and reduced GLUT4 levels. Ectopic expression of haemagglutinin (HA)-tagged GLUT4 conjugated to GFP showed that syntaxin-4-knockout cells retain significant GLUT4 translocation capacity, demonstrating that syntaxin-4 is dispensable for insulin-stimulated GLUT4 translocation. Analysis of recycling kinetics revealed only a modest reduction in the exocytic rate of GLUT4 in knockout cells, and little effect on endocytosis. These analyses demonstrate that syntaxin-4 is not always rate limiting for GLUT4 delivery to the cell surface. In sum, we show that syntaxin-4 knockout results in reduced insulin-stimulated glucose transport, depletion of cellular GLUT4 levels and inhibition of adiponectin secretion but has only modest effects on the translocation capacity of the cells.
Original languageEnglish
Article number258375
Number of pages24
JournalJournal of Cell Science
Volume135
Issue number1
Early online date3 Dec 2021
DOIs
Publication statusPublished - 10 Jan 2022

Keywords

  • GLUT4
  • SNARE
  • syntaxin
  • membrane trafficking

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