Tubular flow activates magnesium transport in the distal convoluted tubule

Abstract

Magnesium (Mg2+) is an important cofactor of many enzymes crucial for life; therefore, maintaining a Mg2+ balance in the body is essential. In the kidney, the distal convoluted tubule (DCT) determines the final urinary Mg2+ excretion. The nephron is subjected to variable urinary flow, but little is known about the influence of flow on Mg2+ transport. Primary cilia, which are mechanosensory organelles that sense changes in flow, are expressed on tubular epithelial cells. This study aimed to elucidate whether urinary flow facilitates DCT Mg2+ transport. To this end, mouse DCT15 cells, with and without primary cilia, were exposed to physiologic fluid flow generating 0.3, 0.6, and 1.2 dyn/cm2 fluid shear stress (FSS). FSS stimulated Mg2+ uptake significantly. Net Mg2+ uptake (i.e., the difference between static and FSS) followed a single component saturable first‐order transport function and was independent of FSS magnitude and primary cilia. FSS did not affect the expression of magnesiotropic genes, including Cnnm2, Kcna1, Proegf, Trpm6, and Trpm7. Transient receptor potential cation channel subfamily melastatin (TRPM) member 7 (Trmp7) inhibition by 2‐aminoethyl diphenyl borinate or knockout of TRPM6 did not alter net Mg2+ uptake, suggesting that TRPM6/TRPM7 homo/heterodimeric channels are not involved in FSS‐activated Mg2+ transport. In summary, FSS generated by physiologic fluid flow is a new factor activating Mg2+ transport in DCT independent of primary cilia.—Verschuren, E. H. J., Hoenderop, J. G. J., Peters, D. J. M., Arjona, F. J., Bindels, R. J. M. Tubular flow activates magnesium transport in the distal convoluted tubule. FASEB J. 33, 5034–5044 (2019). http://www.fasebj.org

Pannexin‐1 mediates fluid shear stress‐sensitive purinergic signaling and cyst growth in polycystic kidney disease

“…Studies have shown that FSS‐modulated ATP release is primary cilia‐dependent . Therefore, Ift140 −/− mDCT15 cells were used, where ciliogenesis is inhibited, to study the ATP extrusion upon FSS mechanosensation . After staining for the primary cilia‐specific protein ARL13B, no primary cilia were detected in Ift140 −/− cells.…”

“…Both Pkd1 −/− clones used in this study were generated independently by either use of the PX458 or PX333‐GFP plasmid. The Ift140 −/− mDCT15 cell line was previously generated and validated by sanger sequencing and immunocytochemistry …”

Flow induces common and specific transcriptional changes in renal tubular epithelial cells involving the PI3K pathway

“…In previous studies, it was shown that several segment-specific transporters are altered due to flow, such as calcium transporters in DCT and CD 50 or magnesium transporters in DCT. 44 Transcriptomic data from tubular cell types not included in this study, e.g. the loop of Henle, and the DCT, will help to complement our understanding of flow-induced effects on cells in renal tubules in the future.…”

Molecular Mechanisms of Renal Magnesium Reabsorption

“…Verschuren and colleagues used an in vitro microfluidic system to determine the effects of fluid shear stress (FSS) on Mg 21 uptake by mDCT15 cells. 67 Mg 21 uptake was stimulated, but the pathways or regulatory mechanisms are unclear. CRISPR/Cas9 disruption of intraflagellar transport 140 homolog (IFT140), which is required for primary cilium function, affected static uptake but had no effect on FSS-induced uptake.…”

“…Changes in fluid flow rate cause shear stress that is detected by primary cilia or mechanosensing proteins located at the apical membrane of the renal epithelia. Verschuren and colleagues used an in vitro microfluidic system to determine the effects of fluid shear stress (FSS) on Mg 2+ uptake by mDCT15 cells 67 . Mg 2+ uptake was stimulated, but the pathways or regulatory mechanisms are unclear.…”