Dietary potassium restriction stimulates endocytosis of ROMK channel in rat cortical collecting duct

Po Yin Chu, Raymond Quigley, Victor Babich, Chou Long Huang

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39 Citations (Scopus)

Abstract

ROMK potassium channels are present in the cortical collecting ducts (CCDs) of the kidney and serve as the exit pathways for K+ secretion in this nephron segment. Dietary K+ 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+ 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+-restricted diet compared with rats fed the control K+ 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+-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 + 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+ homeostasis during K+ deficiency.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Physiology
Volume285
Issue number6 54-6
StatePublished - Dec 2003

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Dietary Potassium
Endocytosis
Staining and Labeling
Diet
Collecting Kidney Tubules
Lysosome-Associated Membrane Glycoproteins
Clathrin-Coated Vesicles
Kidney
Kidney Cortex
Secretory Pathway
Potassium Channels
Nephrons
Xenopus laevis
Proteolysis
Oocytes
Cultured Cells
Homeostasis
Antigens
Membranes

Keywords

  • Clathrin-coated vesicles
  • Confocal imaging
  • Early endosome antigen-1
  • Lysosomal membrane glycoprotein-120

ASJC Scopus subject areas

  • Physiology

Cite this

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title = "Dietary potassium restriction stimulates endocytosis of ROMK channel in rat cortical collecting duct",
abstract = "ROMK potassium channels are present in the cortical collecting ducts (CCDs) of the kidney and serve as the exit pathways for K+ secretion in this nephron segment. Dietary K+ 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+ 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+-restricted diet compared with rats fed the control K+ 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+-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 + 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+ homeostasis during K+ deficiency.",
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T1 - Dietary potassium restriction stimulates endocytosis of ROMK channel in rat cortical collecting duct

AU - Chu, Po Yin

AU - Quigley, Raymond

AU - Babich, Victor

AU - Huang, Chou Long

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N2 - ROMK potassium channels are present in the cortical collecting ducts (CCDs) of the kidney and serve as the exit pathways for K+ secretion in this nephron segment. Dietary K+ 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+ 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+-restricted diet compared with rats fed the control K+ 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+-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 + 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+ homeostasis during K+ deficiency.

AB - ROMK potassium channels are present in the cortical collecting ducts (CCDs) of the kidney and serve as the exit pathways for K+ secretion in this nephron segment. Dietary K+ 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+ 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+-restricted diet compared with rats fed the control K+ 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+-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 + 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+ homeostasis during K+ deficiency.

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