Cited by 64Protease and Inhibitor MechanismsRetinal Diseases and TreatmentsRetinal Development and Disorders

Modulation of cathepsin D activity in retinal pigment epithelial cells

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RAKOCZY, Piroska E., LAI, C. May, BAINES, Michael, GRANDI, Salvatore DI, FITTON, J. Helen, CONSTABLE, Ian J.·1997·Biochemical Journal

Abstract

This project used retinal pigment epithelial (RPE) cells to investigate the effects of up- and down-regulation of cathepsin D expression on the processing of cathepsin D and on the normal phagocytic and digestive function of these cells. RPE cells were transfected with a pHbetaApr-1-neo vector construct carrying the full-length sequence of the translated region of human cathepsin D in sense and antisense directions. Transfected cells were characterized for the presence and expression of the transgene by PCR amplification using transgene-specific primers. Total aspartic proteinase activity present in transformed RPE cells was measured by an enzyme assay using haemoglobin as substrate. Flow cytometry was used to quantify phagocytosis of fluorescein isothiocyanate-labelled rod outer segments (ROS), and lysosomal digestion of ROS was monitored by immunofluorescence. A 435 bp fragment was present in RPE cells carrying the cathepsin D transgene in sense and antisense orientations after PCR amplification. Expression of both 52 kDa procathepsin D and 34 kDa active cathepsin D was significantly up-regulated in sense cathepsin D-transfected RPE cells and down-regulated in RPE cells transfected with antisense cathepsin D. No other forms of cathepsin D were detected in the transfected cells, suggesting that, if pseudo-cathepsin D exists in RPE cells in vivo, it requires the presence of unknown specific regulatory elements. The up- and down-regulation of cathepsin D expression was further confirmed by enzyme assay. Transfected cells retained their phagocytosing ability after ROS challenge and maintained their ability to process ROS. The processing of ROS was significantly slower in RPE cells transfected with antisense than control vector or in sense-cathepsin D-transfected cells. These results demonstrate that cathepsin D is a major proteolytic enzyme participating in the lysosomal digestion of photoreceptor outer segments.

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  • Cathepsin D was reported to degrade OS proteins in vitro, including rhodopsin.

    “It was reported to degrade OS proteins in vitro (Hayasaka et al., 1975; Rakoczy et al., 1997), including rhodopsin (Regan et al., 1980).”

    From The cell biology of the retinal pigment epithelium (2020) · cites this paper as Rakoczy et al., 1997

  • In RPE-J cells, engulfed POS co-localize with LAMP1, LAMP2, and cathepsin D, indicating that POS degradation proceeds.

    “Indeed, we observed that in RPE-J cells engulfed POS co-localized with LAMP1, LAMP2, and cathepsin D (Figure 5A, left panels, arrows) indicating that POS degradation was proceeding (Bosch et al., 1993; Rakoczy et al., 1997; Ramkumar et al., 2010).”

    From Noncanonical autophagy promotes the visual cycle (2013) · cites this paper as Rakoczy et al., 1997

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  1. Gunning, P., Leavitt, J., Muscat, G., Ng, S. and Kedes, L. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 4831-4835
  2. Lin, C., Ng, S., Gunning, P., Kedes, L. and Leavitt, J. (1985) Proc. Natl. Acad. Sci.
  3. Crossman, M., Boulton, M., Marshall, J. and Mellerio, J. (1989) Biochem. Soc. Trans. 302, 1989-1990

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Authors
RAKOCZY, P. E., LAI, C. M., BAINES, M., GRANDI, S. D., FITTON, J. H., & CONSTABLE, I. J.
Affiliations
  • Lions Eye Institute (AU)
  • The University of Western Australia (AU)
Corresponding author
BAINES, Michael
Venue
Biochemical Journal
Published
1997-06-15
Volume
324
Issue
3
Pages
935-940
ISSN
  • 0264-6021 (ISSN-L)
  • 1470-8728
OpenAlex
W1886996198
Cited by
64
References
32
Citations by year
2026: 1 · 2025: 2 · 2022: 1 · 2021: 1 · 2020: 2 · 2019: 2 · 2018: 1 · 2017: 2 · 2016: 2 · 2015: 4 · 2014: 5 · 2013: 3 · 2012: 1
FWCI
1.13
Type
journal article
Language
en
Open access
Locations
  • Biochemical Journal (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • UWA Profiles and Research Repository (University of Western Australia) (submittedVersion)
Funders
  • Université de Montpellier
  • University of California, Los Angeles
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Protease and Inhibitor Mechanisms
  • Health Sciences › Medicine › Ophthalmology › Retinal Diseases and Treatments
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Retinal Development and Disorders
Keywords
cathepsin D, retinal pigment epithelial cells, rod outer segment phagocytosis, lysosomal digestion, aspartic protease, procathepsin D, antisense transfection
MeSH terms
Animals, Cathepsin D, Cattle, Child, Cloning, Molecular, Genetic Vectors, Humans, Phagocytosis, Pigment Epithelium of Eye, Recombinant Proteins, RNA, Messenger, Rod Cell Outer Segment, Transfection, Blotting, Western, Aspartic Acid Endopeptidases

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