Short-term stretch translocates the alpha-1-subunit of the Na pump to plasma membrane |
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Authors: | Sevieux Nancy Ark Mustafa Hornick Conrad Songu-Mize Emel |
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Institution: | (1) Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, 70112 New Orleans, LA;(2) Department of Physiology, Louisiana State University Health Sciences Center, 70112 New Orleans, LA;(3) Present address: Proctor and Gamble, Mason, OH;(4) Present address: Department of Pharmacology, Mersin University, Mersin, Turkey |
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Abstract: | Short-term (2–30 min) cyclic stretch activates the Na pump in cultured aortic smooth muscle cells (ASMCs). This effect of
stretch involves the phosphotidylinositol 3-kinase (PI 3-kinase) participation. Presently, we investigated whether this stimulation
is the result of translocation of Na+,K+-ATPase from endosomes to the plasma membrane. ASMCs were stretched 20% for 5 min using the Flexercell Strain Unit. The plasma
membrane and endosome fractions were isolated and Western blotted to localize the Na+,K+-ATPase α-1-subunit protein. Membrane marker enzyme, 5′ nucleotidase activity, and the early and recycling endosome markers
Rab4 and Rab11 were used to verify the enrichment of these fractions. Stretch increased Na+,K+-ATPase α-1 expression in plasma membrane fractions and decreased it in endosomes. PI 3-kinase inhibitors LY294002 and wortmannin
blocked the stretch-induced translocation of the Na+,K+-ATPase α-1-subunit. Rab4 and Rab11 were enriched in the endosomal fraction, whereas 5′ nucleotidase activity was enriched
in the plasma membrane fraction. We conclude that stimulation of the Na pump activity by shortterm cyclic stretch is the result,
at least in part, of transport of the α-subunit of the enzyme from endosomes to the plasma membrane. |
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Keywords: | Na+ K+-ATPase sodium pump α -isoform cellular translocation cyclic stretch endosomes plasma membrane |
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