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Int. J. Mol. Sci. 2014, 15(1), 1176-1188; doi:10.3390/ijms15011176
Article

Leptin Activates RhoA/ROCK Pathway to Induce Cytoskeleton Remodeling in Nucleus Pulposus Cells

1,†
, 1,†
, 2
, 1
, 2
, 1
 and 1,*
1 Department of Orthopaedic Surgery, Peking Union Medical College Hospital, Peking Union Medical College, Beijing 100730, China 2 Institute of Digestive Disease and State Key Laboratory of Digestive Diseases, Department of Medicine and Therapeutics and LKS Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China These authors contributed equally to this work.
* Author to whom correspondence should be addressed.
Received: 30 November 2013 / Revised: 3 January 2014 / Accepted: 8 January 2014 / Published: 16 January 2014
(This article belongs to the Section Biochemistry, Molecular Biology and Biophysics)
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Abstract

Hyperleptinemia is implicated in obesity-associated lumbar disc degeneration. Nevertheless, the effect of leptin on the intracellular signaling of nucleus pulposus cells is not clear. The current study sought to delineate the possible involvement of the RhoA/ROCK pathway in leptin-mediated cytoskeleton reorganization in nucleus pulposus cells. Nucleus pulposus cells isolated from scoliosis patients were treated with 10 ng/mL of leptin. Fluorescent resonance energy transfer analysis was used to determine the activation of RhoA signaling in nucleus pulposus cells. The protein expression of LIMK1 and cofilin-2 were analyzed by western blot analysis. F-actin cytoskeletal reorganization was assessed by rhodamine-conjugated phalloidin immunoprecipitation. Leptin induced F-actin reorganization and stress fiber formation in nucleus pulposus cells, accompanied by localized RhoA activation and phosphorylation of LIMK1 and cofilin. The RhoA inhibitor C3 exoenzyme or the ROCK inhibitor Y-27632 potently attenuated the effects of leptin on F-actin reorganization and stress fiber formation. Both inhibitors also prevented leptin-induced phosphorylation of LIMK1 and cofilin-2. Our study demonstrated that leptin activated the RhoA/ROCK/LIMK/cofilin-2 cascade to induce cytoskeleton reorganization in nucleus pulposus cells. These findings may provide novel insights into the pathogenic mechanism of obesity-associated lumbar disc degeneration.
Keywords: disc degeneration; fluorescent resonance energy transfer (FRET); cytoskeleton; leptin; F-actin disc degeneration; fluorescent resonance energy transfer (FRET); cytoskeleton; leptin; F-actin
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Li, Z.; Liang, J.; Wu, W.K.K.; Yu, X.; Yu, J.; Weng, X.; Shen, J. Leptin Activates RhoA/ROCK Pathway to Induce Cytoskeleton Remodeling in Nucleus Pulposus Cells. Int. J. Mol. Sci. 2014, 15, 1176-1188.

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