March 2012
Volume 53, Issue 14
ARVO Annual Meeting Abstract  |   March 2012
Systematic Mapping of RPE Phagocytosis Pathways
Author Affiliations & Notes
  • Nora B. Caberoy
    Ophthalmology, Bascom Palmer Eye Inst Univ of Miami, Miami, Florida
  • Yixiong Zhou
    Ophthalmology, Bascom Palmer Eye Inst Univ of Miami, Miami, Florida
  • Gabriela Alvarado
    Ophthalmology, Bascom Palmer Eye Inst Univ of Miami, Miami, Florida
  • Wei Li
    Ophthalmology, Bascom Palmer Eye Inst Univ of Miami, Miami, Florida
  • Footnotes
    Commercial Relationships  Nora B. Caberoy, None; Yixiong Zhou, None; Gabriela Alvarado, None; Wei Li, None
  • Footnotes
    Support  This work is partially supported by NIH R01GM094449-01A1, R01EY016211-05S1, 1K99EY020865-01A1, and an institutional grant from Research to Prevent Blindness
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 3702. doi:
  • Views
  • Share
  • Tools
    • Alerts
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Nora B. Caberoy, Yixiong Zhou, Gabriela Alvarado, Wei Li; Systematic Mapping of RPE Phagocytosis Pathways. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3702.

      Download citation file:

      © ARVO (1962-2015); The Authors (2016-present)

  • Supplements

Purpose: : RPE phagocytosis plays an important role in maintaining retinal homeostasis. Defects in RPE phagocytosis lead to retinal degeneration, and dysfunction in RPE phagocytosis may contribute to age-related macular degeneration. However, daunting challenge to define unknown phagocytosis pathways has hindered our understanding of the physiological and pathological roles of RPE phagocytosis. This study is to systematically identify unknown RPE phagocytosis ligands and receptor-specific phagocytosis ligands.

Methods: : An innovative strategy of phagocytosis-based functional cloning was developed to identify RPE phagocytosis ligands in the absence of receptor information. Furthermore, a novel dual functional cloning technique was developed by combining phagocytosis-based functional cloning with receptor-based affinity cloning to identify receptor-specific RPE phagocytosis ligands. Identified ligands were expressed as recombinant proteins, purified and independently verified by assays for RPE phagocytosis, receptor binding and receptor activation with intracellular signal cascades.

Results: : Phagocytosis-based functional cloning identified tubby and Tulp1 as novel phagocytosis ligands for RPE cells. Both proteins were characterized as bridging molecules for MerTK, a well-known phagocytic receptor. Phagocytic receptor-binding domain (PRBD) of tubby and Tulp1 was mapped to their N-terminal K/R(X)1-2KKK motif(s). PRBP was essential for MerTK binding and receptor phosphorylation induced by tubby and Tulp1. Phagocytosis prey-binding domain (PPBD) of tubby and Tulp1 was mapped to their highly conserved C-terminal 44 amino acids, deletion of which cause retinal degeneration. Removal of either PRBD or PPBD disrupted the bridging function of tubby and Tulp1, abolishing their stimulation of RPE phagocytosis. Dual functional cloning identified galectin-3 (Gal-3) as new MerTK-specific phagocytosis ligand. Similar to tubby and Tulp1, Gal-3 was also characterized as a new bridging molecule for MerTK to facilitate RPE phagocytosis.

Conclusions: : These results identified three new phagocytosis ligands for MerTK. These studies demonstrated that phagocytosis-based functional cloning is a valid technology for unbiased identification of RPE phagocytosis ligands in the absence of receptor information and that dual functional cloning is valid for systematic identification of receptor-specific RPE phagocytosis ligands. These technologies will improve our capability to systematically map RPE phagocytosis ligands, receptors and signaling pathways, and open a new chapter for RPE molecular phagocyte biology and exploration of their therapeutic potentials.

Keywords: retinal degenerations: cell biology • phagocytosis and killing • retinal pigment epithelium 

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.