Role of lipid rafts in membrane delivery of renal epithelial Na+-K+-ATPase, thick ascending limb
| Autor: | Michele Salanova, Jan-Henning Frühauf, David A. Groneberg, Sebastian Bachmann, Pia Welker, Beate Geist, Eberhard Krause |
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| Rok vydání: | 2006 |
| Předmět: |
Male
Physiology Glycosylphosphatidylinositols Vasopressins Sodium-Potassium-Exchanging ATPase Detergents Biology medicine.disease_cause Kidney Rats Sprague-Dawley Membrane Microdomains Mucoproteins Physiology (medical) Protein targeting Uromodulin medicine Animals Na+/K+-ATPase Lipid raft Cells Cultured Antidiuretic Agents Epithelial Cells Raft respiratory system Membrane transport Immunohistochemistry Cell biology Rats medicine.anatomical_structure Cholesterol Biochemistry Membrane protein lipids (amino acids peptides and proteins) Rabbits |
| Zdroj: | American journal of physiology. Regulatory, integrative and comparative physiology. 292(3) |
| ISSN: | 0363-6119 |
| Popis: | Lipid rafts are cholesterol- and shingolipid-enriched membrane microdomains implicated in membrane signaling and trafficking. To assess renal epithelial raft functions through the characterization of their associated membrane proteins, we have isolated lipid rafts from rat kidney by sucrose gradient fractionation after detergent treatment. The low-density fraction was enriched in cholesterol, sphingolipid, and flotillin-1 known as lipid raft markers. Based on proteomic analysis of the low-density fraction, the protein with the highest significance score was the α-subunit of Na+-K+-ATPase (NKA), whose raft association was validated by simultaneous immunoblotting. The β-subunit of NKA was copurified from the low-density fraction. To test the role of lipid rafts in sorting and membrane delivery of renal-transporting epithelia, we have chosen to study thick ascending limb (TAL) epithelium for its high NKA activity and the property to be stimulated by antidiuretic hormone (ADH). Cultured rabbit TAL cells were studied. Cholesterol depletion and detergent extraction at warmth caused a shift of NKA to the higher-density fractions. Comparative preparations from blood monocytes revealed the absence of NKA from rafts in these nonpolarized cells. Short-term exposure of rabbit TAL cells to ADH (1 h) caused translocation and enhanced raft association of NKA via cAMP activation. Preceding cholesterol depletion prevented this effect. TAL-specific, glycosylphosphatidylinositol-anchored Tamm Horsfall protein was copurified with NKA in the same raft fraction, suggesting functional interference between these products. These results may have functional implications regarding the turnover, trafficking, and regulated surface expression of NKA as the major basolateral ion transporter of TAL. |
| Databáze: | OpenAIRE |
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