Related Experiment Video

Updated: Jun 20, 2026

Live Images of GLUT4 Protein Trafficking in Mouse Primary Hypothalamic Neurons Using Deconvolution Microscopy
08:47

Live Images of GLUT4 Protein Trafficking in Mouse Primary Hypothalamic Neurons Using Deconvolution Microscopy

Published on: December 7, 2017

Insulin-stimulated phosphorylation of the Rab GTPase-activating protein TBC1D1 regulates GLUT4 translocation

Grantley R Peck1, Jose A Chavez, William G Roach

  • 1Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.

The Journal of Biological Chemistry
|September 11, 2009
PubMed

Insights

Insulin-stimulated glucose transporter GLUT4 (glucose transporter type 4) translocation is enabled by Akt phosphorylation of TBC1D1 in muscle cells. This regulation is crucial for glucose uptake and resembles that of its paralog, AS160.

Area of Science:

  • * Cellular biology
  • * Molecular endocrinology
  • * Metabolic regulation

Background:

  • * Insulin promotes glucose transporter type 4 (GLUT4) translocation to the plasma membrane in muscle and fat cells.
  • * Akt phosphorylation of AS160 (TBC1D4) is known to trigger GLUT4 translocation by inhibiting its GTPase-activating protein activity.
  • * The role of the related protein TBC1D1, primarily in muscle, in this process remained unclear.

Purpose of the Study:

  • * To investigate the role of TBC1D1 in insulin-stimulated GLUT4 translocation.
  • * To identify key phosphorylation sites on TBC1D1 regulated by Akt.
  • * To examine the impact of TBC1D1 variants and AMPK activation on GLUT4 translocation.

Main Methods:

  • * Utilized C2C12 myotubes to study insulin signaling pathways.
  • * Employed site-directed mutagenesis to create alanine substitution mutants of TBC1D1.
  • * Assessed GLUT4 translocation in response to insulin, Akt activation, and AMP-dependent protein kinase (AMPK) activation.

Main Results:

  • * Identified potential Akt phosphorylation sites on TBC1D1 in response to insulin.
  • * A TBC1D1 mutant lacking key Akt phosphorylation sites significantly inhibited insulin-stimulated GLUT4 translocation compared to wild-type.
  • * AMPK activation partially relieved TBC1D1-mediated inhibition of GLUT4 translocation. The obesity-associated R125W TBC1D1 variant showed similar inhibitory effects to wild-type TBC1D1.

Conclusions:

  • * Akt-mediated phosphorylation of TBC1D1 is essential for enabling insulin-stimulated GLUT4 translocation.
  • * TBC1D1 regulation in GLUT4 translocation mirrors that of its paralog, AS160.
  • * TBC1D1 function in glucose transport is independent of its R125W variant and is comparable between healthy and type 2 diabetic individuals.

More Related Videos

Detection of Detergent-sensitive Interactions Between Membrane Proteins10:09

Detection of Detergent-sensitive Interactions Between Membrane Proteins

Published on: March 7, 2018

Quantitative Measurement of GLUT4 Translocation to the Plasma Membrane by Flow Cytometry05:39

Quantitative Measurement of GLUT4 Translocation to the Plasma Membrane by Flow Cytometry

Published on: November 7, 2010

Related Concept Videos

Insulin: The Receptor and Signaling Pathways01:28

Insulin: The Receptor and Signaling Pathways

Insulin action is mediated through a receptor tyrosine kinase, akin to the IGF-1 receptor. The number of receptors per cell varies significantly, from 40 on erythrocytes to 300,000 on adipocytes and hepatocytes. The insulin receptor consists of linked α/β subunit dimers, forming a heterotetramer glycoprotein with two extracellular α subunits and two β subunits spanning the membrane. The α subunits inhibit the inherent tyrosine kinase activity of the β subunits, but this inhibition is released...
Insulin Secretory Vesicles01:05

Insulin Secretory Vesicles

Insulin secretory vesicles release insulin to stimulate blood glucose uptake and regulate carbohydrate metabolism. When the blood glucose levels increase, glucose enters the pancreatic β-islet cells through glucose transporters. Once inside, glucose is metabolized through glycolysis, the citric acid cycle, and the electron transport chain, producing ATP. This increase in ATP concentration closes ATP-sensitive potassium channels, leading to depolarization of the membrane and the opening of...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...
Rab Cascades01:25

Rab Cascades

Rab GTPases act in a regulated cascade during membrane fusion, helping the lipid bilayers mix. The Rab family of proteins are active when bound to GTP, and inactive when bound to GDP. Hence, they act as guanine nucleotide-dependent molecular switches. Rab-GTP recognizes and binds to long or short-range tethering proteins to capture the target vesicle. These tethers coordinate with SNAREs on the vesicle and the target membrane to assemble the trans SNARE complex that locks the mixing bilayers.
Rab Proteins01:14

Rab Proteins

Rab proteins constitute the largest family of monomeric GTPases, of which 70 members are present in humans. Rab proteins and their effectors regulate consecutive stages of vesicle transport such as vesicle transport, docking, and fusion to the correct recipient membrane.
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
cAMP-dependent Protein Kinase Pathways01:25

cAMP-dependent Protein Kinase Pathways

Cyclic Adenosine Monophosphate (cAMP) is an essential second messenger that activates protein kinase A (PKA) and regulates various biological processes. A single epinephrine molecule binds to GPCR and activates several heterotrimeric G proteins, each stimulating multiple adenylyl cyclase, amplifying the signal, and synthesizing large numbers of cAMP molecules. Small changes in cAMP concentration affect PKA activity. The binding of four cAMP molecules induces a conformational change in PKA,...