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Organelle tethering by a homotypic PDZ interaction underlies formation of the Golgi membrane network

Debrup Sengupta1, Steven Truschel, Collin Bachert

  • 1Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.

The Journal of Cell Biology
|July 8, 2009
PubMed

Insights

Golgi ribbon formation relies on GRASP65, a protein that tethers organelles via its PDZ domain. This study reveals a homotypic PDZ interaction mechanism for organelle tethering in living cells.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The Golgi apparatus's ribbon-like structure is crucial for its function.
  • GM130 and GRASP65 are known to be involved in Golgi ribbon formation, but the underlying mechanism remains unclear.

Purpose of the Study:

  • To elucidate the mechanism by which GRASP65 mediates organelle tethering and Golgi ribbon formation.
  • To investigate the role of the GRASP65 PDZ domain in these processes.

Main Methods:

  • Development of an in vivo organelle tethering assay using mitochondria targeted with GRASP65.
  • Utilizing point mutations within the GRASP65 PDZ domain to assess its function.
  • Employing a gene replacement assay to evaluate Golgi ribbon formation.

Main Results:

  • GRASP65 targeted to mitochondria induced tethering of these organelles.
  • Tethering was dependent on the GRASP65 PDZ domain and its ability to self-interact.
  • A specific point mutation in the GRASP65 PDZ domain abolished both mitochondrial tethering and Golgi ribbon formation.
  • Membrane anchoring of the PDZ domain was necessary for efficient tethering, suggesting a trans-acting mechanism.

Conclusions:

  • A homotypic PDZ interaction mediated by GRASP65 is a key mechanism for organelle tethering in living cells.
  • This interaction is essential for the formation of the Golgi ribbon-like membrane network.

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