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[The double-play of PP17/TIP47]

Alain Pauloin1, Michèle Ollivier-Bousquet, Eric Chanat

  • 1Unité de Génomique et physiologie de la lactation, Inra, 78352 Jouy-en-Josas, France. pauloin@jouy.inra.fr

Medecine Sciences : M/S
|November 5, 2004
PubMed

Insights

The protein TIP47, also known as PP17b, is crucial for transporting mannose 6-phosphate receptors. This ubiquitous protein also plays a role in lipid droplet traffic, suggesting a dual function in cellular processes.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mannose 6-phosphate receptors are essential for lysosomal enzyme targeting.
  • The intracellular transport mechanisms of these receptors are not fully understood.
  • TIP47 (also known as PP17b) has been identified as a key player in receptor recycling.

Purpose of the Study:

  • To elucidate the role of TIP47 in the retrograde transport of mannose 6-phosphate receptors.
  • To investigate the potential dual functions of TIP47 in both receptor trafficking and lipid metabolism.
  • To explore the homology of TIP47 with lipid droplet-associated proteins.

Main Methods:

  • Protein identification and characterization.
  • Analysis of protein-protein interactions (e.g., with Rab9-GTP).
  • Homology studies comparing TIP47 with adipophilin and perilipins.
  • Investigation of TIP47's association with lipid droplets.

Main Results:

  • TIP47, in complex with Rab9-GTP, mediates the return of mannose 6-phosphate receptors from late endosomes to the trans-Golgi network.
  • TIP47 shares sequence homology with lipid droplet proteins (adipophilin, perilipins) and is associated with lipid droplets.
  • Previous studies identified PP17b (homologous to TIP47) as a placental protein and a cancer biomarker.

Conclusions:

  • TIP47 is a multifunctional protein involved in distinct cellular transport pathways.
  • The discovery of TIP47's role provides a missing link in understanding mannose 6-phosphate receptor trafficking.
  • A hypothesis is proposed regarding how TIP47 integrates roles in receptor and lipid droplet transport.

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