Retinal Degeneration Protein 3 (RD3) in normal human tissues: Novel insights

Abstract

The 195-amino-acid-long human Retinal Degeneration Protein 3 (RD3) is critical in the regulation of guanylate cyclase (GC) signaling and photoreceptor cell survival. Recently, we identified significant loss of RD3 in high-risk neuroblastoma and the influential role of RD3 in tumor progression. However, the functional characterization of RD3 in tumor systems has been hampered by the dearth of information on its localization in normal tissue and by the lack of antibodies suitable for staining FFPE tissue, primarily due to the inaccessibility of the epitopes. In this study, we validated a custom-synthesized RD3 antibody and investigated the expression/localization of RD3 in assorted human tissues. We observed stratified expression of RD3 in different cell types and subcellular location of retina. We demonstrated extensive positive RD3 immunoreactivity in various normal tissues and particularly strong dot-like perinuclear staining in the lining epithelial cells, suggesting that RD3 may play an important role in the normal functioning of epithelial cells. RD3 expression is limited in the CNS. While neuroblastoma is often RD3-positive, the adrenal medulla, where many neuroblastomas originate, is RD3-negative. Meta-analysis of RD3 transcriptional expression across normal tissues confirmed tissue-specific RD3 mRNA levels. Our results revealed the tissue-specific expression/localization profile of RD3 for the first time.

Control of the Nucleotide Cycle in Photoreceptor Cell Extracts by Retinal Degeneration Protein 3

“…Guanylate kinase regulation by RD3 might not be restricted to photoreceptor cells ( Lavorgna et al, 2003 ; Azadi, 2013 ), since recent studies revealed that RD3 is also found in other tissue types like epithelial cells and is more ubiquitously expressed ( Aravindan et al, 2017 ). Additionally, the authors suggest a metastasis suppressor function for RD3 in neuroblastoma ( Khan et al, 2015 ).…”

“…These findings are, however, in disagreement with a previous study showing that inactivation of both RD3 alleles in LCA12 patients does not correlate with extraocular symptoms ( Perrault et al, 2013 ). Recently, RD3 immunoreactivity was detected in normal human cell types, in particular in epithelial cells ( Aravindan et al, 2017 ).…”

De novo regulation of RD3 synthesis in residual neuroblastoma cells after intensive multi-modal clinical therapy harmonizes disease evolution

“…However, beyond retinal localization and functions in retinal degeneration, the physiognomy and functions of RD3 are unknown. We were the first to define the distribution of constitutive RD3 expression and localization in healthy human tissues 28 . Although researchers reported RD3 co-localization with the tumor suppressor PML 34 , the functional significance of RD3 in cancer biology is unknown.…”

“…All TMA construction, RD3 IHC, and positivity scoring was performed and quantified as discussed in our earlier studies 27,28 . Dissemination of tumors to vital organs in PD were assessed by a pathologist (ZY) utilizing H&E- and synaptophysin (marker for NB) -stained sections.…”

“…High-throughput (miRNA, cGH) characterization of this model recognized acquisition of genetic/molecular rearrangements in disease evolution 25–27 . We demonstrated that Retinal Degeneration Protein 3 (RD3), which is constitutively expressed in human tissues 28 , has a regulatory role in NB evolution, and RD3 loss (i) contributes to the altered metastatic state of the NB cells in vitro and (ii) pathogenesis of disease progression in vivo , and (iii) is associated with advanced disease stage and poor clinical outcomes 29 .…”