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Author Notes:

Address for reprint requests and other correspondence: G. Chen, Renal Division, Emory Univ. School of Medicine, WMRB Rm. 338, 1639 Pierce Dr., NE, Atlanta, GA 30322 (e-mail: gchen3@emory.edu).

Subjects:

Research Funding:

This work was supported by National Institutes of Health Grants R01-DK087838 and R21-DK080431 (to G. Chen).

Keywords:

  • cytoskeletal protein
  • latrunculin
  • membrane protein
  • urea transport

Depolymerization of cortical actin inhibits UT-A1 urea transporter endocytosis but promotes forskolin-stimulated membrane trafficking

Tools:

Journal Title:

American Journal of Physiology - Cell Physiology

Volume:

Volume 302, Number 7

Publisher:

, Pages C1012-C1018

Type of Work:

Article | Post-print: After Peer Review

Abstract:

The cytoskeleton participates in many aspects of transporter protein regulation. In this study, by using yeast two-hybrid screening, we identified the cytoskeletal protein actin as a binding partner with the UT-A1 urea transporter. This suggests that actin plays a role in regulating UT-A1 activity. Actin specifically binds to the carboxyl terminus of UT-A1. A serial mutation study shows that actin binding to UT-A1's carboxyl terminus was abolished when serine 918 was mutated to alanine. In polarized UT-A1-MDCK cells, cortical filamentous (F) actin colocalizes with UT-A1 at the apical membrane and the subapical cytoplasm. In the cell surface, both actin and UT-A1 are distributed in the lipid raft microdomains. Disruption of the F-actin cytoskeleton by latrunculin B resulted in UT-A1 accumulation in the cell membrane as measured by biotinylation. This effect was mainly due to inhibition of UT-A1 endocytosis in both clathrin and caveolin-mediated endocytic pathways. In contrast, actin depolymerization facilitated forskolin-stimulated UT-A1 trafficking to the cell surface. Functionally, depolymerization of actin by latrunculin B significantly increased UT-A1 urea transport activity in an oocyte expression system. Our study shows that cortical F-actin not only serves as a structural protein, but directly interacts with UT-A1 and plays an important role in controlling UT-A1 cell surface expression by affecting both endocytosis and trafficking, therefore regulating UT-A1 bioactivity.

Copyright information:

© 2012 the American Physiological Society

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