The subcellular localization control of integrin linked kinase 1 through its protein-protein interaction with caveolin-1.
Integrin linked kinase 1 (ILK1), a member of the serine/threonine kinases, has been shown to be crucial for the cell survival, differentiation, and Wnt signaling. Firstly, by using a confocal microscopy and a transfection approach, we obtained the evidence that ILK1 interacts physically with caveolin-1, a 22-kDa integral membrane protein, which is the principal structural and regulatory component of caveolae membranes. By ILK1 deletion mutant analysis, we characterized the caveolin-1-binding domain in the kinase domain of ILK1. In addition, we found that native ILK1 is associated with endogenous caveolin-1 in COS-1 cells. Secondly, transient transfection assays showed that a reduction in caveolin-1 binding leads to a substantial increase in the serine/threonine phosphorylation of ILK1. Thirdly, caveolin-1 and its scaffolding peptide (amino acids 82-101) functionally suppressed the auto-kinase activity of purified recombinant ILK1 protein. Fourthly, the association of ILK1 with caveolin-1 regulated its cytoplasmic retention; if it was not associated with caveolin-1, it was transported to the nucleus. Fifthly, we also noticed the putative nuclear localization sequences (nls) in ILK1 near the caveolin-1-binding domain. Thus, our data indicate that caveolin-1 regulates ILK1 auto-phosphorylation activity and its subcellular localization via a specific protein-protein interaction through blocking the exposure of its putative nls motif.
Chun
Jaesun
J
School of Science Education and Bio-Research Institute, Chungbuk National University, Gaeshin-dong, Heungdok-gu, Chongju, Chungbuk 361-763, Republic of Korea.
Hyun
Sunghee
S
Kwon
Taegun
T
Lee
Eun Jeoung
EJ
Hong
Soon-Kwang
SK
Kang
Sang Sun
SS
D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism*; D002522:Chlorocebus aethiops; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D000099200:Scaffold Protein ILK
D051242:Caveolin 1; D022461:Caveolins; D017346:Protein Serine-Threonine Kinases; D012694:Serine; D000099200:Scaffold Protein ILK