Bidirectional transport of 2-chloroadenosine by equilibrative nucleoside transporter 4 (hENT4): Evidence for allosteric kinetics at acidic pH
Adenosine has been reported to be transported by equilibrative nucleoside transporter 4 (ENT4), encoded by the SLC29A4 gene, in an acidic pH-dependent manner. This makes hENT4 of interest as a therapeutic target in acidic pathologies where adenosine is protective (e.g. vascular ischaemia). We examin...
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Veröffentlicht in: | Scientific reports 2019-09, Vol.9 (1), p.13555-14, Article 13555 |
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Sprache: | eng |
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Zusammenfassung: | Adenosine has been reported to be transported by equilibrative nucleoside transporter 4 (ENT4), encoded by the
SLC29A4
gene, in an acidic pH-dependent manner. This makes hENT4 of interest as a therapeutic target in acidic pathologies where adenosine is protective (e.g. vascular ischaemia). We examined the pH-sensitivity of nucleoside influx and efflux by hENT4 using a recombinant transfection model that lacks the confounding influences of other nucleoside transporters (PK15-NTD). We established that [
3
H]2-chloroadenosine, which is resistant to metabolism by adenosine deaminase, is a substrate for hENT4. Transport of [
3
H]2-chloroadenosine at a pH of 6.0 in PK15-NTD cells stably transfected with
SLC29A4
was biphasic, with a low capacity (V
max
~ 30 pmol/mg/min) high-affinity component (K
m
~ 50 µM) apparent at low substrate concentrations, which shifted to a high capacity (V
max
~ 500 pmol/mg/min) low affinity system (K
m
> 600 µM) displaying positive cooperativity at concentrations above 200 µM. Only the low affinity component was observed at a neutral pH of 7.5 (K
m
~ 2 mM). Efflux of [
3
H]2-chloroadenosine from these cells was also enhanced by more than 4-fold at an acidic pH. Enhanced influx and efflux of nucleosides by hENT4 under acidic conditions supports its potential as a therapeutic target in pathologies such as ischaemia-reperfusion injury. |
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ISSN: | 2045-2322 2045-2322 |
DOI: | 10.1038/s41598-019-49929-w |