Shank2 redistributes with NaPilla during regulated endocytosis.
Serum phosphate levels are acutely impacted by the abundance of sodium-phosphate cotransporter IIa (NaPiIIa) in the apical membrane of renal proximal tubule cells. PSD-95/Disks Large/Zonula Occludens (PDZ) domain-containing proteins bind NaPiIIa and likely contribute to the delivery, retention, recovery, and trafficking of NaPiIIa. Shank2 is a distinctive PDZ domain protein that binds NaPiIIa. Its role in regulating NaPiIIa activity, distribution, and abundance is unknown. In the present in vivo study, rats were maintained on a low-phosphate diet, and then plasma phosphate levels were acutely elevated by high-phosphate feeding to induce the recovery, endocytosis, and degradation of NaPiIIa. Western blot analysis of renal cortical tissue from rats given high-phosphate feed showed NaPiIIa and Shank2 underwent degradation. Quantitative immunofluorescence analyses, including microvillar versus intracellular intensity ratios and intensity correlation quotients, showed that Shank2 redistributed with NaPiIIa during the time course of NaPiIIa endocytosis. Furthermore, NaPiIIa and Shank2 trafficked through distinct endosomal compartments (clathrin, early endosomes, lysosomes) with the same temporal pattern. These in vivo findings indicate that Shank2 is positioned to coordinate the regulated endocytic retrieval and downregulation of NaPiIIa in rat renal proximal tubule cells.
Dobrinskikh
Evgenia
E
Department of Medicine, Anschutz Medical Center, University of Colorado, Denver, Colorado, USA.
Giral
Hector
H
Caldas
Yupanqui A
YA
Levi
Moshe
M
Doctor
R Brian
RB
D000818:Animals; D002966:Clathrin / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D007672:Kidney Cortex / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D008871:Microvilli / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000378:metabolism*; D010710:Phosphates / Q000097:blood; D016226:Phosphorus, Dietary / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa / Q000032:analysis / Q000378:metabolism*
D002966:Clathrin; D009419:Nerve Tissue Proteins; D010710:Phosphates; D016226:Phosphorus, Dietary; C485686:Shank2 protein, rat; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa
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