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V-type ATPase is involved in biogenesis of GLUT4 vesicles

Marina Malikova1, Jun Shi, Konstantin V Kandror

  • 1Boston University School of Medicine, Boston, Massachusetts 02118, USA.

American Journal of Physiology. Endocrinology and Metabolism
|May 29, 2004
PubMed

Insights

Proton pumps are crucial for glucose transporter 4 (GLUT4) vesicle formation in adipocytes. Inhibiting these pumps blocks insulin-regulated glucose transport by preventing the development of responsive GLUT4 vesicles.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Physiology

Background:

  • Proton pumps, specifically V-type ATPases, are known to be involved in endocytic protein trafficking.
  • The precise role of proton pumps in the GLUT4 pathway, critical for glucose uptake in adipocytes, has been debated.

Purpose of the Study:

  • To investigate the specific role of V-type ATPase proton pumps in insulin-regulated GLUT4 trafficking in 3T3-L1 adipocytes.
  • To determine whether proton pump inhibition affects GLUT4 vesicle formation and translocation.

Main Methods:

  • Treatment of 3T3-L1 adipocytes with specific V-type ATPase inhibitors: concanamycin A and bafilomycin A1.
  • Assessment of insulin-regulated glucose transport.
  • Analysis of GLUT4 localization and vesicle dynamics using cell fractionation and microscopy.

Main Results:

  • Inhibition of V-type ATPase with concanamycin A and bafilomycin A1 significantly reduced insulin-regulated glucose transport.
  • These inhibitors caused GLUT4 to accumulate in heavy intracellular membranes and decreased the population of small, responsive GLUT4 vesicles.
  • Proton pump inhibitors did not impede the translocation of existing vesicles or GLUT4 sorting in recycling endosomes.
  • Wortmannin, a different inhibitor, affected existing vesicle translocation but not vesicle formation.

Conclusions:

  • V-type ATPase proton pumps are essential for the formation of small, insulin-responsive GLUT4 vesicles in adipose cells.
  • These pumps act upstream of vesicle translocation, specifically inhibiting the formation of GLUT4-containing vesicles on donor intracellular membranes.
  • The findings clarify the controversial role of proton pumps in GLUT4 trafficking and suggest distinct mechanisms for vesicle formation versus translocation.

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