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A dynein loading zone for retrograde endosome motility at microtubule plus-ends

J H Lenz1, I Schuchardt, A Straube

  • 1Max-Planck-Institut für terrestrische Mikrobiologie, Marburg, Germany.

The EMBO Journal
|May 12, 2006
PubMed

Insights

In Ustilago maydis, endosomes move to the hyphal tip via Kinesin-3 motors and return via dynein motors. This dynein-dependent retrograde transport is crucial for hyphal growth and membrane recycling.

Area of Science:

  • Cell biology
  • Mycology
  • Molecular motor function

Background:

  • Early endosomes are essential for membrane recycling and hyphal growth in Ustilago maydis.
  • Bidirectional movement of endosomes along microtubules (MTs) facilitates localized growth at the hyphal tip.

Purpose of the Study:

  • To elucidate the molecular mechanism governing bidirectional endosome transport in Ustilago maydis hyphae.
  • To identify the motor proteins and regulatory factors involved in endosome trafficking.

Main Methods:

  • Microtubule-based motor protein analysis (Kinesin-3, dynein).
  • Genetic manipulation (null mutants, depletion of activators).
  • Live-cell imaging of endosome and motor protein dynamics (GFP-tagged dynein).

Main Results:

  • Endosomes move apically via Kinesin-3 and retrogradely via dynein.
  • Dynein, dynactin, and Lis1 accumulate at apical MT plus-ends, forming a reservoir for retrograde transport.
  • Defects in Lis1 or Kinesin-1 disrupt dynein/dynactin targeting and abolish endosome traffic.
  • GFP-dynein exhibits retrograde, not anterograde, movement on endosomes.

Conclusions:

  • An apical dynein loading zone in the hyphal tip facilitates efficient retrograde endosome transport.
  • This mechanism ensures endosomes reach the growth region before reversing direction, supporting hyphal tip expansion.

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