PINCH-1 is an obligate partner of integrin-linked kinase (ILK) functioning in cell shape modulation, motility, and survival.
PINCH-1 is a widely expressed focal adhesion protein that forms a ternary complex with integrin-linked kinase (ILK) and CH-ILKBP/actopaxin/alpha-parvin (abbreviated as alpha-parvin herein). We have used RNA interference, a powerful approach of reverse genetics, to investigate the functions of PINCH-1 and ILK in human cells. We report here the following. First, PINCH-1 and ILK, but not alpha-parvin, are essential for prompt cell spreading and motility. Second, PINCH-1 and ILK, like alpha-parvin, are crucial for cell survival. Third, PINCH-1 and ILK are required for optimal activating phosphorylation of PKB/Akt, an important signaling intermediate of the survival pathway. Whereas depletion of ILK reduced Ser473 phosphorylation but not Thr308 phosphorylation of PKB/Akt, depletion of PINCH-1 reduced both the Ser473 and Thr308 phosphorylation of PKB/Akt. Fourth, PINCH-1 and ILK function in the survival pathway not only upstream but also downstream (or in parallel) of protein kinase B (PKB)/Akt. Fifth, PINCH-1, ILK and to a less extent alpha-parvin are mutually dependent in maintenance of their protein, but not mRNA, levels. The coordinated down-regulation of PINCH-1, ILK, and alpha-parvin proteins is mediated at least in part by proteasomes. Finally, increased expression of PINCH-2, an ILK-binding protein that is structurally related to PINCH-1, prevented the down-regulation of ILK and alpha-parvin induced by the loss of PINCH-1 but failed to restore the survival signaling or cell shape modulation. These results provide new insights into the functions of PINCH proteins in regulation of ILK and alpha-parvin and control of cell behavior.
Fukuda
Tomohiko
T
Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
Chen
Ka
K
Shi
Xiaohua
X
Wu
Chuanyue
C
D000185:Actinin / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis; D002465:Cell Movement; D002468:Cell Physiological Phenomena; D048429:Cell Size; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D060588:LIM Domain Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D000099200:Scaffold Protein ILK; D000096985:Calponins
D000185:Actinin; D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; D060588:LIM Domain Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D017346:Protein Serine-Threonine Kinases; D034741:RNA, Small Interfering; D000099200:Scaffold Protein ILK; C088088:LIMS1 protein, human; C486590:PARVA protein, human; D000096985:Calponins; C486591:PARVB protein, human