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Characterization of the in vitro retrograde transport of MPR46

Guruprasad Ramarao Medigeshi1, Peter Schu

  • 1Georg-August Universität Göttingen, Zentrum für Biochemie und Molekulare Zellbiologie, Biochemie II, Heinrich-Düker-Weg-12, D-37073 Goettingen, Germany.

Traffic (Copenhagen, Denmark)
|November 18, 2003
PubMed

Insights

The mannose 6-phosphate receptor (MPR46) recycles from endosomes to the Golgi. This retrograde transport relies on specific proteins like SNAREs and Rab6, and adaptor protein AP-3.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The mannose 6-phosphate receptor (MPR46) is crucial for directing lysosomal enzymes to their destination.
  • MPR46 cycles between the trans-Golgi network (TGN) and endosomes, a process vital for cellular function.

Purpose of the Study:

  • To investigate the molecular mechanisms governing the retrograde transport of MPR46 from endosomes back to the TGN.
  • To identify key proteins and pathways involved in MPR46 recycling.

Main Methods:

  • Utilized an in vitro transport assay with mouse fibroblast cell lines.
  • Measured sulfation of modified MPR46 upon TGN entry as an indicator of successful transport.
  • Employed specific peptides and genetic deficiencies (AP-1) to probe transport requirements.

Main Results:

  • Retrograde transport of MPR46 is time-, temperature-, ATP-, and cytosol-dependent.
  • The process requires SNARE proteins (Vti1a, Syntaxin 16) and Rab6, and is sensitive to GTPγS and brefeldin A.
  • Transport is dependent on cytosolic AP-3 and inhibited by a peptide containing the acidic cluster-di-leucine motif, implicating AP-3 in MPR46 retrograde sorting.

Conclusions:

  • MPR46 utilizes an early endosome-to-TGN retrograde transport route.
  • The study highlights the essential roles of SNAREs, Rab6, and AP-3 in MPR46 recycling.
  • Findings provide insights into the molecular machinery of lysosomal enzyme sorting and receptor trafficking.

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