PMID- 33605986
OWN - NLM
STAT- MEDLINE
DCOM- 20210720
LR  - 20210720
IS  - 1552-5783 (Electronic)
IS  - 0146-0404 (Print)
IS  - 0146-0404 (Linking)
VI  - 62
IP  - 2
DP  - 2021 Feb 1
TI  - Degradation of Photoreceptor Outer Segments by the Retinal Pigment Epithelium 
      Requires Pigment Epithelium-Derived Factor Receptor (PEDF-R).
PG  - 30
LID - 10.1167/iovs.62.2.30 [doi]
LID - 30
AB  - PURPOSE: To examine the contribution of pigment epithelium-derived factor 
      receptor (PEDF-R) to the phagocytosis process. Previously, we identified PEDF-R, 
      the protein encoded by the PNPLA2 gene, as a phospholipase A2 in the retinal 
      pigment epithelium (RPE). During phagocytosis, RPE cells ingest abundant 
      phospholipids and protein in the form of photoreceptor outer segment (POS) tips, 
      which are then hydrolyzed. The role of PEDF-R in RPE phagocytosis is not known. 
      METHODS: Mice in which PNPLA2 was conditionally knocked out (cKO) in the RPE were 
      generated. Mouse RPE/choroid explants were cultured. Human ARPE-19 cells were 
      transfected with siPNPLA2 silencing duplexes. POSs were isolated from bovine 
      retinas. The phospholipase A2 inhibitor bromoenol lactone was used. Transmission 
      electron microscopy, immunofluorescence, lipid labeling, pulse-chase experiments, 
      western blots, and free fatty acid and beta-hydroxybutyrate assays were performed. 
      RESULTS: The RPE of the cKO mice accumulated lipids, as well as more abundant and 
      larger rhodopsin particles, compared to littermate controls. Upon POS exposure, 
      RPE explants from cKO mice released less beta-hydroxybutyrate compared to controls. 
      After POS ingestion during phagocytosis, rhodopsin degradation was stalled both 
      in cells treated with bromoenol lactone and in PNPLA2-knocked-down cells relative 
      to their corresponding controls. Phospholipase A2 inhibition lowered 
      beta-hydroxybutyrate release from phagocytic RPE cells. PNPLA2 knockdown also 
      resulted in a decline in fatty acids and beta-hydroxybutyrate release from 
      phagocytic RPE cells. CONCLUSIONS: PEDF-R downregulation delayed POS digestion 
      during phagocytosis. The findings imply that the efficiency of RPE phagocytosis 
      depends on PEDF-R, thus identifying a novel contribution of this protein to POS 
      degradation in the RPE.
FAU - Bullock, Jeanee
AU  - Bullock J
AD  - Section of Protein Structure and Function, Laboratory of Retinal Cell and 
      Molecular Biology, National Eye Institute, National Institutes of Health, 
      Bethesda, Maryland, United States.
AD  - Department of Biochemistry and Molecular & Cellular Biology, Georgetown 
      University Medical Center, Washington DC, United States.
FAU - Polato, Federica
AU  - Polato F
AD  - Section of Protein Structure and Function, Laboratory of Retinal Cell and 
      Molecular Biology, National Eye Institute, National Institutes of Health, 
      Bethesda, Maryland, United States.
FAU - Abu-Asab, Mones
AU  - Abu-Asab M
AD  - Section of Histopathology, National Eye Institute, National Institutes of Health, 
      Bethesda, Maryland, United States.
FAU - Bernardo-Colon, Alexandra
AU  - Bernardo-Colon A
AD  - Section of Protein Structure and Function, Laboratory of Retinal Cell and 
      Molecular Biology, National Eye Institute, National Institutes of Health, 
      Bethesda, Maryland, United States.
FAU - Aflaki, Elma
AU  - Aflaki E
AD  - Section of Protein Structure and Function, Laboratory of Retinal Cell and 
      Molecular Biology, National Eye Institute, National Institutes of Health, 
      Bethesda, Maryland, United States.
FAU - Agbaga, Martin-Paul
AU  - Agbaga MP
AD  - Departments of Cell Biology and Ophthalmology, Dean McGee Eye Institute, 
      University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United 
      States.
FAU - Becerra, S Patricia
AU  - Becerra SP
AD  - Section of Protein Structure and Function, Laboratory of Retinal Cell and 
      Molecular Biology, National Eye Institute, National Institutes of Health, 
      Bethesda, Maryland, United States.
LA  - eng
GR  - R01 EY030513/EY/NEI NIH HHS/United States
PT  - Journal Article
PT  - Research Support, N.I.H., Extramural
PT  - Research Support, N.I.H., Intramural
PL  - United States
TA  - Invest Ophthalmol Vis Sci
JT  - Investigative ophthalmology & visual science
JID - 7703701
RN  - 0 (Receptors, Neuropeptide)
RN  - 0 (pigment epithelium-derived factor receptor)
RN  - 9007-49-2 (DNA)
SB  - IM
MH  - Animals
MH  - Blotting, Western
MH  - Cells, Cultured
MH  - DNA/*genetics
MH  - DNA Mutational Analysis
MH  - Disease Models, Animal
MH  - Mice, Transgenic
MH  - *Mutation
MH  - Phagocytosis
MH  - Receptors, Neuropeptide/*genetics/metabolism
MH  - Retinal Diseases/*genetics/metabolism/pathology
MH  - Retinal Photoreceptor Cell Outer Segment/*metabolism/pathology
MH  - Retinal Pigment Epithelium/*metabolism/pathology
PMC - PMC7900850
COIS- Disclosure: J. Bullock, None; F. Polato, None; M. Abu-Asab, None; A. 
      Bernardo-Colon, None; E. Aflaki, None; M.P. Agbaga, None; S.P. Becerra, None
EDAT- 2021/02/20 06:00
MHDA- 2021/07/21 06:00
PMCR- 2021/02/19
CRDT- 2021/02/19 12:11
PHST- 2021/02/19 12:11 [entrez]
PHST- 2021/02/20 06:00 [pubmed]
PHST- 2021/07/21 06:00 [medline]
PHST- 2021/02/19 00:00 [pmc-release]
AID - 2772309 [pii]
AID - IOVS-20-31418 [pii]
AID - 10.1167/iovs.62.2.30 [doi]
PST - ppublish
SO  - Invest Ophthalmol Vis Sci. 2021 Feb 1;62(2):30. doi: 10.1167/iovs.62.2.30.