van Eerde, A. | bioRxiv Science

bioRxiv2020

The lysosomal V-ATPase B1 subunit in proximal tubule is linked to nephropathic cystinosis

Variants in ATP6V1B1, the gene encoding the B1 subunit of the vacuolar H+-ATPase lead to distal renal tubular acidosis and hearing loss of variable degree. Apart from metabolic acidosis, a 23-month-old girl with pathogenic ATP6V1B1 variants presented with increased granulocyte cystine levels, and symptoms of renal Fanconi syndrome, indicating an unknown link to proximal tubulopathy and cystinosis, a disorder of the proximal tubule caused by variants in the CTNS gene. Here, we demonstrated that ATP6V1B1 is expressed in proximal tubules of human kidney tissue, though to a lesser extent than in distal tubules. Further, we used CRISPR/Cas9 technology to selectively knockout ATP6V1B1 or CTNS in human renal proximal tubule cells and performed a full metabolomic and proteomic analysis to compare their phenotype to isogenic control cells. In line with the clinical data, the loss of ATP6V1B1 disrupted the chemiosmotic coupling between the lysosomal V ATPase B1 subunit and cystinosin and resulted in intralysosomal accumulation of cystine and autophagy activation in renal proximal tubule cells. In conclusion, we identified ATP6V1B1 as a central player in renal proximal tubule cells, regulating lysosomal cystine transport and autophagy, and its absence can lead to proximal tubule dysfunction.

pharmacology and toxicology↗

bioRxiv2018

Transcriptome and metabolome analysis provide insights into root and root released organic anion responses to phosphorus deficiency in oat

Root and root-released organic anions play important roles in uptake of phosphorus (P), an essential macronutrient for food production. Oat, ranking sixth in the worlds cereal production, contains valuable nutritional compounds and can withstand poor soil conditions. The aim of this research was to investigate root transcriptional and metabolic responses of oat grown under P-deficient and P-sufficient conditions. We conducted a hydroponic experiment and measured root morphology, organic anions exudation, and analysed changes in the transcriptome and metabolome, to understand oat root adaptation to P deficiency. We found that oat roots showed enhanced citrate and malate exudation after four weeks of P-deficiency. After 10 days of P-deficiency, we identified 9371 differentially expressed transcripts with a two-fold or greater change (p < 0.05): forty-eight sequences predicted to be involved in organic anion biosynthesis and efflux were consistently up-regulated; twenty-four up-regulated transcripts in oat were also found up-regulated upon P starvation in rice and wheat under similar conditions. Phosphorylated metabolites (i.e. glucose-6-phosphate, myo-inositol-phosphate) reduced dramatically, while citrate and malate, some sugars and amino acids increased slightly in P-deficient oat roots. Our data provide new insights into the root responses to P deficiency and root-released organic anions in oat.\n\nHighlightWe found oat- a monocot food crop, showed high exudation rate of citrate under phosphorus deficiency; root transcriptome and metabolome were then investigated to understand oat adaptation to P deficiency.

plant biology↗