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mBet3p is required for homotypic COPII vesicle tethering in mammalian cells

Sidney Yu1, Ayano Satoh, Marc Pypaert

  • 1Howard Hughes Medical Institute and Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06519, USA.

The Journal of Cell Biology
|August 2, 2006
PubMed

Insights

Mammalian Bet3p (mBet3p), a conserved TRAPP subunit, is crucial for vesicular tubular cluster (VTC) formation by mediating COPII vesicle tethering and fusion. Its depletion disrupts Golgi architecture and causes cargo accumulation.

Area of Science:

  • Cell biology
  • Molecular and cell biology
  • Protein complex function

Background:

  • TRAPPI complex tethers COPII vesicles to the Golgi in yeast.
  • In mammalian cells, COPII vesicles form vesicular tubular clusters (VTCs) via homotypic tethering.
  • The role of TRAPPI subunits in mammalian VTC biogenesis is unclear.

Purpose of the Study:

  • To investigate the function of mammalian Bet3p (mBet3p), a conserved TRAPP subunit, in VTC biogenesis.
  • To determine if mBet3p is required for COPII vesicle tethering and fusion in mammalian cells.

Main Methods:

  • Immunofluorescence microscopy to localize mBet3p on the transitional ER (tER) and VTCs.
  • In vitro assay to reconstitute VTC biogenesis and assess mBet3p's role in vesicle tethering and fusion.
  • siRNA-mediated depletion of mBet3p to analyze effects on ERGIC-53 localization and Golgi architecture.

Main Results:

  • mBet3p localizes to the tER and VTCs.
  • mBet3p inactivation leads to cargo accumulation colocalizing with COPII coat.
  • In vitro assays show mBet3p is essential for COPII vesicle tethering and fusion.
  • mBet3p depletion disrupts ERGIC-53 localization and Golgi architecture.

Conclusions:

  • The TRAPPI complex, specifically mBet3p, is essential for mammalian VTC biogenesis.
  • mBet3p plays a critical role in the homotypic tethering and fusion of COPII vesicles.
  • Disruption of mBet3p function impairs ER-to-Golgi transport and cellular organization.

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