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In vivo and in vitro Studies of Adaptor-clathrin Interaction
17:14

In vivo and in vitro Studies of Adaptor-clathrin Interaction

Published on: January 26, 2011

Differential clathrin binding and subcellular localization of OCRL1 splice isoforms

Rawshan Choudhury1, Christopher J Noakes, Edward McKenzie

  • 1Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, United Kingdom.

The Journal of Biological Chemistry
|February 13, 2009
PubMed

Insights

The inositol polyphosphate 5-phosphatase OCRL1 has two isoforms that affect clathrin binding differently. Isoform a binds clathrin more strongly, impacting endocytosis, suggesting distinct functional roles in cellular trafficking.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • OCRL1 mutations cause Lowe syndrome, affecting brain, kidney, and eye development.
  • OCRL1 has two splice isoforms (a and b) differing by 8 amino acids.
  • The functional significance of OCRL1 splicing and its impact on protein interactions remain unclear.

Purpose of the Study:

  • To investigate the impact of OCRL1 splicing on its interaction with clathrin.
  • To determine how OCRL1 isoforms differ in their association with clathrin-coated vesicles.
  • To elucidate the role of OCRL1 in clathrin-mediated endocytosis.

Main Methods:

  • Comparative analysis of clathrin binding affinity between OCRL1 isoforms a and b.
  • Immunofluorescence and biochemical assays to detect enrichment in clathrin-coated trafficking intermediates.
  • Functional assays examining transferrin endocytosis in cells expressing OCRL1 variants.
  • Investigation of OCRL1 interaction with Rab GTPases and AP2.

Main Results:

  • OCRL1 isoform a exhibits higher affinity for clathrin compared to isoform b.
  • Isoform a is significantly more enriched in clathrin-coated trafficking intermediates.
  • A second clathrin-binding site was identified in OCRL1.
  • OCRL1 association with clathrin-coated intermediates depends on membrane association via Rab GTPases, not AP2.
  • Expression of OCRL1 isoform a lacking the 5-phosphatase domain impairs transferrin endocytosis, unlike isoform b.

Conclusions:

  • OCRL1 splicing generates two functional pools with distinct roles in clathrin-mediated trafficking.
  • Isoform a plays a significant role in clathrin-mediated endocytosis, while isoform b has a lesser or no role.
  • These findings provide insights into the molecular mechanisms underlying Lowe syndrome and cellular trafficking pathways.

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