Uptake of leptin and albumin via separate pathways in proximal tubule cells.
The adipokine leptin and oncotic protein albumin are endocytosed in the proximal tubule via the scavenger receptor megalin. Leptin reduces megalin expression and activates cell signalling pathways that upregulate fibrotic protein expression. The aim of this study was to investigate if leptin uptake in proximal tubule cells was via the albumin-megalin endocytic complex. In immortalised proximal tubule Opossum kidney cells (OK) fluorescent leptin and albumin co-localised following 5min exposure, however there was no co-localisation at 10, 20 and 30min exposure. In OK cells, acute exposure to leptin for 2h did not alter NHE3, ClC-5, NHERF1 and NHERF2 mRNA. However, acute leptin exposure increased NHERF2 protein expression in proximal tubule cells. In OK cells, immunoprecipitation experimentation indicated leptin did not bind to ClC-5. Leptin uptake in OK cells was enhanced by bafilomycin and ammonium chloride treatment, demonstrating that uptake was not dependent on lysosomal pH. Thus, it is likely that two pools of megalin exist in proximal tubule cells to facilitate separate uptake of leptin and albumin by endocytosis.
Centre For Chronic Disease, College of Health and Biomedicine, Victoria University, St. Albans, VIC 3021, Australia; Department of Physiology, The University of Melbourne, Parkville, Melbourne, VIC 3010, Australia.
Jessica F
JF
Briffa
Centre For Chronic Disease, College of Health and Biomedicine, Victoria University, St. Albans, VIC 3021, Australia.
Esther
E
Grinfeld
School of Medical Sciences, The Bosch Institute, The University of Sydney, NSW 2006, Australia.
Philip
P
Poronnik
Centre For Chronic Disease, College of Health and Biomedicine, Victoria University, St. Albans, VIC 3021, Australia.
Andrew J
AJ
McAinch
Centre For Chronic Disease, College of Health and Biomedicine, Victoria University, St. Albans, VIC 3021, Australia; Department of Physiology, The University of Melbourne, Parkville, Melbourne, VIC 3010, Australia. Electronic address: Deanne.Skelly@unimelb.edu.au.
Deanne H
DH
Hryciw
D000418:Albumins / Q000378:metabolism*; D000818:Animals; D018118:Chloride Channels / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D020738:Leptin / Q000378:metabolism*; D008247:Lysosomes / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D013997:Time Factors
D000418:Albumins; D018118:Chloride Channels; D020738:Leptin; D017923:Sodium-Hydrogen Exchangers
Albumin; Leptin; Megalin; NHERF2; Proximal tubule