期刊
CELLULAR SIGNALLING
卷 21, 期 1, 页码 120-127出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.cellsig.2008.09.016
关键词
Rho GTPases; Rho kinases; Nucleotide receptor; High density lipoprotein (HDL); Apolipoprotein A-l
类别
Cell surface receptors for high-density lipoprotein (HDL) on hepatocytes are major partners in the regulation of cholesterol homeostasis. We have previously demonstrated on human hepatocytes that apolipoprotein A-l binding to an ectopic F-1-ATPase stimulates the production of extracellular ADP that activates a P2Y(13)-mediated high-density lipoprotein (HDL) endocytosis pathway. However, P2Y(13)-dependent signalling pathway has never been described yet. The current study demonstrates a major role of cytoskeleton reorganization in F-1-ATPase/P2Y(13)-dependent HDL endocytosis under the control of the small GTPase RhoA and its effector ROCK I. Indeed human hepatocytes (HepG(2) cells) stimulated by ADP or AR-C69931MX (both P2Y(13) agonists) showed a high specific activation of RhoA; in addition, inhibition of Rho proteins by C3 exoenzyme impairs HDL endocytosis whereas a constitutively active form of RhoA stimulates HDL endocytosis at the same level as under F-1-ATPase/P2Y(13) activation. Pharmacological inhibition of ROCK activity decreased HDL endocytosis following stimulation by apoA-l (F-1-ATPase ligand), ADP or AR-C69931MX and specific siRNA ROCK I extinction prevented the stimulation of HDL endocytosis without effect of ROCK H extinction. The functional involvement of ROCK I downstream F-1-ATPase/P2Y(13) was confirmed by the strong enrichment of the membrane fraction in ROCK I and by the requirement of actin polymerization in hepatocyte HDL endocytosis. These results allow the identification of the molecular events downstream P2Y(13) receptor activation for a better understanding of hepatocyte HDL endocytosis, the latest step in reverse cholesterol transport. (C) 2008 Elsevier Inc. All rights reserved.
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