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This document is an editorial published in Frontiers in Physiology titled "Renal physiology: epithelial cell mechanics." The editorial emphasizes the importance of understanding the mechanical properties of renal epithelial cells in both health and disease. It highlights key themes in epithelial cell mechanics, including energy balance, fluid and electrolyte transport, and primary cilium function. The editorial also discusses the role of renal epithelial cell mechanics in kidney disorders such as obesity-related kidney diseases, acute kidney injury, and diabetic kidney disease. The document concludes by acknowledging the contributions of the authors and reviewers to the research topic. [Extracted from the article]

ROMK potassium channels are present in the cortical collecting ducts (CCDs) of the kidney and serve as the exit pathways for [K.sup.+] secretion in this nephron segment. Dietary [K.sup.+] restriction reduces the abundance of ROMK in the kidney. We have previously shown that ROMK undergoes endocytosis via clathrin-coated vesicles in Xenopus laevis oocytes and in cultured cells. Here, we examined the effect of dietary [K.sup.+] restriction on endocytosis of ROMK in CCDs using double-labeling immunofluorescent staining and confocal microscopic imaging in whole kidney sections as well as in individually isolated tubules. We found that ROMK abundance in kidney cortex and CCDs was reduced in rats fed a [K.sup.+]-restricted diet compared with rats fed the control [K.sup.+] diet. In the control animals, ROMK staining was preferentially localized to the apical membrane of CCDs. Compared with control tubules, ROMK staining in CCDs was markedly shifted toward intracellular locations in animals fed a [K.sup.+]-deficient diet for 48 h. Some of the intracellular distribution of ROMK colocalized with an early endosomal marker, early endosomal antigen-1 or with a late endosomal/lysosomal marker, lysosomal membrane glycoprotein-120. These results suggest that [K.sup.+] restriction reduces the abundance of ROMK in CCDs by increasing endocytosis and degradation of the channel protein. This decrease in the abundance of ROMK is likely important for maintaining [K.sup.+] homeostasis during [K.sup.+] deficiency. early endosome antigen-1; lysosomal membrane glycoprotein-120; clathrin-coated vesicles; confocal imaging

ROMK channels are present in the cortical collecting ducts of kidney and are responsible for [K.sup.+] secretion in this nephron segment. Recent studies suggest that endocytosis of ROMK channels is important for regulation of [K.sup.+] secretion in cortical collecting ducts. We investigated the molecular mechanisms for endocytosis of ROMK channels expressed in Xenopus laevis oocytes and cultured Madin-Darby canine kidney cells. When plasma membrane insertion of newly synthesized channel proteins was blocked by incubation with brefeldin A, ROMK currents decreased with a half-time of ~6 h. Coexpression with the Lys44[right arrow]Ala dominant-negative mutant dynamin, but not wild-type dynamin, reduced the rate of reduction of ROMK in the presence of brefeldin A. Mutation of Asn371 to Ile in the putative NPXY internalization motif of ROMK1 abolished the effect of the Lys44[right arrow]Ala dynamin mutant on endocytosis of the channel. Coimmunoprecipitation study and confocal fluorescent imaging revealed that ROMK channels associated with clathrin coat proteins in Madin-Darby canine kidney cells. These results provide compelling evidence for endocytosis of ROMK channels via clathrin-coated vesicles. dominant-negative dynamin; Madin-Darby canine kidney cells; brefeldin A; Xenopus laevis oocytes; tyrosine-based consensus motif

A high renal oxygen (O2) need is primarily associated with the renal tubular O2 consumption (VO2) necessary for a high rate of sodium (Na+) transport. Limited O2 availability leads to increased levels of adenosine, which regulates the kidney via activation of both A1 and A2A adenosine receptors (A1R and A2AR, respectively). The relative contributions of A1R and A2AR to the regulation of renal Na+ transport and VO2 have not been determined. We demonstrated that A1R activation has a dose‐dependent biphasic effect on both renal Na+/H+ exchanger‐3 (NHE3), a major player in Na+ transport, and VO2. Here, we report concentration‐dependent effects of adenosine: less than 5 × 10−7 M adenosine‐stimulated NHE3 activity; between 5 × 10−7 M and 10−5 M adenosine‐inhibited NHE3 activity; and greater than 10−5 M adenosine reversed the change in NHE3 activity (returned to baseline). A1R activation mediated the activation and inhibition of NHE3 activity, whereas 10−4 M adenosine had no effect on the NHE3 activity due to A2AR activation. The following occurred when A1R and A2AR were activated: (a) Blockade of the A2AR receptor restored the NHE3 inhibition mediated by A1R activation, (b) the NHE‐dependent effect on VO2 mediated by A1R activation became NHE independent, and (c) A2AR bound to A1R. In summary, A1R affects VO2 via NHE‐dependent mechanisms, whereas A2AR acts via NHE‐independent mechanisms. When both A1R and A2AR are activated, the A2AR effect on NHE3 and VO2 predominates, possibly via an A1R–A2AR protein interaction. A2AR–A1R heterodimerization is proposed as the molecular mechanism enabling the NHE‐independent control of renal VO2. [ABSTRACT FROM AUTHOR]