Differential Expression of ATP7A, ATP7B and CTR1 in Adult Rat Dorsal Root Ganglion Tissue

Abstract

BackgroundATP7A, ATP7B and CTR1 are metal transporting proteins that control the cellular disposition of copper and platinum drugs, but their expression in dorsal root ganglion (DRG) tissue and their role in platinum-induced neurotoxicity are unknown. To investigate the DRG expression of ATP7A, ATP7B and CTR1, lumbar DRG and reference tissues were collected for real time quantitative PCR, RT-PCR, immunohistochemistry and Western blot analysis from healthy control adult rats or from animals treated with intraperitoneal oxaliplatin (1.85 mg/kg) or drug vehicle twice weekly for 8 weeks.ResultsIn DRG tissue from healthy control animals, ATP7A mRNA was clearly detectable at levels similar to those found in the brain and spinal cord, and intense ATP7A immunoreactivity was localised to the cytoplasm of cell bodies of smaller DRG neurons without staining of satellite cells, nerve fibres or co-localisation with phosphorylated heavy neurofilament subunit (pNF-H). High levels of CTR1 mRNA were detected in all tissues from healthy control animals, and strong CTR1 immunoreactivity was associated with plasma membranes and vesicular cytoplasmic structures of the cell bodies of larger-sized DRG neurons without co-localization with ATP7A. DRG neurons with strong expression of ATP7A or CTR1 had distinct cell body size profiles with minimal overlap between them. Oxaliplatin treatment did not alter the size profile of strongly ATP7A-immunoreactive neurons but significantly reduced the size profile of strongly CTR1-immunoreactive neurons. ATP7B mRNA was barely detectable, and no specific immunoreactivity for ATP7B was found, in DRG tissue from healthy control animals.ConclusionsIn conclusion, adult rat DRG tissue exhibits a specific pattern of expression of copper transporters with distinct subsets of peripheral sensory neurons intensely expressing either ATP7A or CTR1, but not both or ATP7B. The neuron subtype-specific and largely non-overlapping distribution of ATP7A and CTR1 within rat DRG tissue may be required to support the potentially differing cuproenzyme requirements of distinct subsets of sensory neurons, and could influence the transport and neurotoxicity of oxaliplatin.

Oxaliplatin Transport Mediated by Organic Cation/Carnitine Transporters OCTN1 and OCTN2 in Overexpressing Human Embryonic Kidney 293 Cells and Rat Dorsal Root Ganglion Neurons

“…However, OCT expression is known to influenced by many factors, including animal species, gender, strain, disease, and exposures (Koepsell et al, 2007); therefore, our study does not rule out the possibility of OCTs having a significant role in the uptake of oxaliplatin by DRG neurons in contexts other than as explicitly studied. We recently showed a specific pattern of expression of copper transporters in rat DRG tissue (Ip et al, 2010) and that CTR1-expressing DRG neurons become atrophied after oxaliplatin treatment (Liu et al, 2009). The relative contributions of copper transporters, OCTs, and OCTNs to the neurotoxicity of oxaliplatin remain to be determined definitively.…”

Oxaliplatin-induced neurotoxicity is dependent on the organic cation transporter OCT2

“…These phenotypic changes occurred in the absence of any detectable changes in the expression of other transporter genes (Table S1) of putative relevance to oxaliplatin (Fig. 6), including the ATP-binding cassette transporter family c2 [Abcc2; Multidrug resistance-associated protein 2 (Mrp2)] (25), the organic cation transporter, novel, type 1 [Octn1, encoded by the solute carrier family member 22a4 (Slc22a4)] (26), the coppertransporting ATPase 1 (Atp7a) and the copper transporter 1 [Ctr1, encoded by the solute carrier family member 31a1 (Slc31a1)] (27,28). Additionally, both sensitivity to mechanical stimuli and cold occurred in the absence of any histological damage (Fig.…”

Membrane Transporters as Mediators of Cisplatin Effects and Side Effects

“…Conversely, ATP7A was localized to the cytoplasm of cell bodies of smaller DRG neurons without staining of satellite cells and nerve fibres, while high levels of Ctr1 were detected in plasma membranes and vesicular cytoplasmic structures of the cell bodies of larger-sized DRG neurons without colocalization with ATP7A [55]. The authors of this study suggest that it is possible that ATP7A-expressing DRG neurons are less sensitive to oxaliplatin neurotoxicity because the high levels of ATP7A facilitate the cellular efflux of oxaliplatin reducing its availability for reactions with DNA or other key neurotoxicity targets.…”