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Ciliary targeting motif VxPx directs assembly of a trafficking module through Arf4

Jana Mazelova1, Lisa Astuto-Gribble, Hiroki Inoue

  • 1Division of Ophthalmology, Department of Surgery, University of New Mexico, Albuquerque, NM 87131, USA.

The EMBO Journal
|January 21, 2009
PubMed

Insights

Researchers identified a novel ciliary targeting motif (VxPx) in rhodopsin. This motif interacts with Arf4, regulating membrane protein transport to cilia and preventing retinal degeneration.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • Primary cilia dysfunction is linked to human diseases, including retinal degeneration.
  • Mechanisms of membrane protein targeting to cilia are not fully understood.

Purpose of the Study:

  • To elucidate the molecular mechanisms of ciliary membrane protein targeting.
  • To identify key proteins and pathways involved in cargo selection for cilia.

Main Methods:

  • Identified the VxPx motif in rhodopsin and its interaction with Arf4.
  • Investigated the role of the Arf4-based targeting complex (Arf4, Rab11, FIP3, ASAP1) at the trans-Golgi network (TGN).
  • Utilized transgenic animal models with Arf4 mutations to study rhodopsin trafficking and retinal degeneration.

Main Results:

  • The VxPx motif binds Arf4, influencing its association with the TGN and the assembly of a ciliary targeting complex.
  • ASAP1 mediates GTP hydrolysis on Arf4, regulating the budding of post-TGN carriers.
  • An Arf4 mutant (I46D) impaired in GTP hydrolysis led to aberrant rhodopsin trafficking and retinal degeneration.

Conclusions:

  • The Arf4-based complex is crucial for selecting and packaging ciliary membrane proteins.
  • The VxPx motif and Arf4 pathway represent a conserved mechanism for ciliary cargo delivery.
  • Dysregulation of this pathway contributes to retinal degeneration, highlighting potential therapeutic targets.

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