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Originally published In Press as doi:10.1167/iovs.08-2616 on April 1, 2009
 (Investigative Ophthalmology and Visual Science. 2009;50:5759-5768.)
© 2009 by The Association for Research in Vision and Ophthalmology, Inc.
doi:10.1167/iovs.08-2616
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Subtilisin-like Proprotein Convertase Expression, Localization, and Activity in the Human Retina and Optic Nerve Head

John A. Fuller, Anne-Marie Brun-Zinkernagel, Abbot F. Clark, and Robert J. Wordinger

From the Department of Cell Biology and Genetics, University of North Texas Health Science Center, Fort Worth, Texas.

Corresponding author: John A. Fuller, Wilmer Eye Institute, Johns Hopkins University School of Medicine, 400 N Broadway, The Robert and Clarice Smith Building, Room 3001, Baltimore, MD 21287; jfulle19{at}jhmi.edu.

Purpose. Subtilisin-like proprotein convertases (SPCs) are a family of calcium-dependent cleavage enzymes that act on dibasic sites of various peptide/protein substrates. The purpose of this study was to investigate the expression, localization, and activity of SPCs in the human retina and optic nerve head.

Methods. mRNA expression of the SPC family in the human retina and optic nerve head tissues was evaluated by quantitative reverse transcription polymerase chain reaction (QRT-PCR). Double immunofluorescence staining was performed on paraffin-embedded human posterior sections to localize SPC family members. Western blot analysis was used to identify PACE4 isoform expression within the optic nerve head and retina. In addition, a fluorogenic SPC substrate-based assay was used to elucidate SPC enzyme activity within human retina and optic nerve head (ONH) tissues.

Results. QPCR results indicated that PC1 and PC2 were expressed 4.1- and 5.7-fold higher in retina compared to optic nerve head, whereas PACE4 was expressed 4.1-fold higher in the ONH. PC1 and PC2 were localized primarily in neuronal cells, whereas PACE4 and PC5 were limited to the glia of the retina and optic nerve head. SPC activity in ONH lysate was significantly higher than that of retinal lysate; however, when an SPC inhibitor was added, activity in ONH decreased more than that in retina.

Conclusions. These results indicate that the SPCs are expressed in distinct patterns throughout the human retina and ONH. PC1 and PC2 were primarily expressed in neurons, whereas PACE4 appeared to be largely restricted to glia. Thus, elevated PACE4 may modulate the bioactivity of proteins secreted in the ONH and retina.






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