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Tayler Faye Lesleigh Wishart, Frank J Lovicu; PROFILING HEPARAN SULFATE PROTEOGLYCAN EXPRESSION IN THE LENS.. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3179. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Proteoglycans are glycoproteins comprised of a core protein and covalently attached glycosaminoglycan (GAG) chains that localise to the cell surface and/or extracellular matrix. Proteoglycans associated with sulfated GAG chains (eg. heparan sulfate proteoglycans; HSPGs) are required for the interaction of growth factors with their cognate receptors. Recent studies from our laboratory observed that impaired HSPG sulfation potently and reversibly blocks rat lens epithelial cell (LEC) proliferation induced by ocular mitogens, suggesting an important regulatory role for HSPGs in LEC behaviour. To better understand the role of the different HSPGs in lens, here we compare their expression and spatial localisation, and investigate how differentially altering their sulfation impacts on LEC mitogenesis.
We analysed the expression of all known cellular and secreted HSPGs using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), in the lens. Spatial differences in HSPG localisation were investigated using immunolabelling of mid-sagittal sections and lens epithelial whole mounts from 10-day-old Wistar rat lens. Using lens epithelial explants, we investigated the effects of different inhibitors of HSPG/GAG sulfation (eg. sodium chlorate, surfen) on growth factor-induced LEC proliferation (BrdU-incorporation) and downstream signaling pathways (eg. Western blotting of MAPK/ERK1/2).
Both cellular (syndecans and glypicans) and secreted HSPGs (eg. perlecan) were differentially expressed in 10-day old rat lens, and localised strongly to the germinative zone, and lens capsule, respectively. Functionally, we observed that lens cell proliferation and downstream signalling pathways induced by ocular mitogens were markedly reduced in the presence of the different inhibitors of HSPG/GAG sulfation.
The differential expression of different basement membrane and cell surface HSPGs suggests that specific HSPGs may be involved in the regulation of LEC behaviour. Taken together with previous work from our lab, these data support a requirement for HSPG/GAG sulfation in mitogen-induced signalling in the lens. By further characterising and specifically modulating these sulfated proteins, we hope to develop novel ways of regulating cell behaviour that will not only be relevant to lens biology and disease, but may extend to other growth factor-mediated pathologies.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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