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This Article Full Text Full Text (PDF) All Versions of this Article: 289/4/F826    most recent 00412.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Ziembicki, J. Articles by Huang, C. Search for Related Content PubMed PubMed Citation Articles by Ziembicki, J. Articles by Huang, C.

Mechanical force-activated phospholipase D is mediated by G_12/13-Rho and calmodulin-dependent kinase in renal epithelial cells

Departments of ¹Surgery and ⁴Medicine, Case Western Reserve University; ³Rammelkamp Center for Research and Education, MetroHealth System Campus, and ²Louis Stokes Veterans Affairs Medical Center, Cleveland, Ohio

Submitted 18 November 2004 ; accepted in final form 9 May 2005

The renal glomerulus, the site of plasma ultrafiltration, is exposed to mechanical force in vivo arising from capillary blood pressure and fluid flow. Studies of cultured podocytes demonstrate that they respond to stretch by altering the structure of the actin cytoskeleton, but the mechanisms by which physical force triggers this architectural change and the signaling pathways that lead to generation of second messengers are not defined. In the present study, we found that in renal epithelial cells [podocytes and Madin-Darby canine kidney (MDCK) cells], application of mechanical force to the cell surface through fibronectin-coated ferric beads and exposure of the cells to magnetic force lead to Rho translocation and actin cytoskeleton reorganization. This application of force recruited Rho and filamentous actin (F-actin) to bead loci and subsequently stimulated phospholipase D (PLD), a downstream effector of Rho. Using MDCK cells that stably express regulators of G protein-signaling (RGS) proteins [RGS4 attenuates G_i and G_q, and the p115RhoGEF-RGS domain (p115-RGS) attenuates G_12/13] to define the signaling pathway, we found that mechanical force induced G_12/13-Rho activation and increased F-actin to stimulate PLD activity. The activation can be partially prevented by the C₃ exoenzyme. Pretreatment of the cells with chemical inhibitors of several kinases showed that calmodulin-dependent kinase is also involved in stretch-induced PLD activation by a separate pathway. Taken together, our data demonstrate that in cultured podocytes and MDCK cells, mechanical force leads to actin cytoskeleton reorganization and PLD activation. The signaling pathways for PLD activation involve G_12/13/Rho/F-actin and calmodulin-dependent kinase.

podocytes; signaling

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