Disease relevance of ILK

• Western blot analyses indicated very low levels of ParvB protein in MDA-MB-231 and MCF7 breast cancer cells, facilitating functional studies of the effects of ParvB on ILK signaling [1].
• Our initial results indicate that therapeutic strategies targeting ILK may be beneficial in the treatment of glioblastomas [2].
• To determine the role of ILK in the cellular radiation response, stably transfected A549 lung cancer cells overexpressing either wild-type (ILK-wk) or hyperactive ILK (ILK-hk) were studied for survival, signaling, proliferation, and examined in immunofluorescence and adhesion assays [3].
• These results demonstrate that alpha(v) integrins regulate ovarian cancer cell proliferation through ILK [4].
• In addition, ILK activity and expression are elevated in adenomatous polyposis and colon carcinomas [5].

High impact information on ILK

• We propose that ILK is a receptor-proximal protein kinase regulating integrin-mediated signal transduction [6].
• Overexpression of p59ILK disrupted epithelial cell architecture and inhibited adhesion to integrin substrates, while inducing anchorage-independent growth [6].
• Regulation of cell adhesion and anchorage-dependent growth by a new beta 1-integrin-linked protein kinase [6].
• We report here that this integrin-linked kinase (ILK) phosphorylated a beta 1-integrin cytoplasmic domain peptide in vitro and coimmunoprecipitated with beta 1 in lysates of mammalian cells [6].
• One of these is integrin-linked kinase, which connects integrins to the actin cytoskeleton and transduces signals through integrins to the extracellular matrix and from integrins to various subcellular compartments [7].

Chemical compound and disease context of ILK

• Levels of ILK expression affect gemcitabine chemoresistance in pancreatic adenocarcinoma cells [8].
• ILK may be a sensitive and specific immunohistochemical marker and useful for the positive identification of ES and PNET in formalin-fixed, paraffin-embedded tissue sections [9].
• Involvement of integrin-linked kinase in carbon tetrachloride-induced hepatic fibrosis in rats [10].
• In addition, impaired ILK kinase activity results in significant reduction of integrin-dependent invasion mediated by invasins of two other important pathogens, Staphylococcus aureus and Yersinia spp [11].
• In ovarian carcinoma xenografts, ABT-627, a specific ET(A)R antagonist, suppresses ILK expression, Akt and glycogen synthase kinase-3beta phosphorylation, and tumor growth [12].

Biological context of ILK

• Furthermore, dominant-negative ILK or WT PTEN induces G(1) phase cycle arrest and enhanced apoptosis [13].
• Transfection of dominant-negative ILK and WT PTEN into these cells also results in the inhibition of PKB/Akt kinase activity [13].
• Inhibition of ILK suppressed this LPS-stimulated IkappaB phosphorylation and degradation [14].
• Here we demonstrate, using several different approaches, that inhibiting ILK kinase activity, or expression, results in the inhibition of cell attachment, cell migration, F-actin organization, and the specific cytoskeletal localization of CH-ILKBP and paxillin in human cells [15].
• These data demonstrate that the kinase and adaptor properties of ILK function together, in a Pi3 kinase-dependent manner, to regulate integrin-mediated cell attachment and signal transduction [15].

Anatomical context of ILK

• In this report we demonstrate that VEGF-induced vessel morphogenesis of human umbilical vein endothelial cells (HUVEC) was inhibited by the transfection of a dominant negative, kinase-deficient ILK (ILK-KD), as well as by treatment with the phosphatidylinositol 3-kinase inhibitor LY294002 [16].
• The above results raise the potential for regulation of MP activity in platelet cytoskeleton by ILK and suggest an alternative to the Rho-linked pathway [17].
• This interaction localizes ILK to focal adhesion plaques [18].
• Previously, we identified an integrin-linked kinase (ILK)-binding protein affixin (beta-parvin), which links initial integrin signals to rapid actin reorganization, and thus plays critical roles in fibroblast migration [19].
• Cloning of ILK from rat smooth muscle cells generated a cDNA that exhibited 99.6% identity at the amino acid level with human ILK-1 [20].

Associations of ILK with chemical compounds

• We recently have demonstrated that the integrin-linked kinase (ILK) can phosphorylate PKB/Akt on Ser-473 in a phosphoinositide phospholipid-dependent manner [13].
• Genetic studies in Drosophila, Caenorhabditis elegans, and mice point to an essential role of ILK as an adaptor protein in mediating integrin-dependent cell attachment and cytoskeletal organization [15].
• The amino acid residue serine 343 of ILK within the activation loop is required for kinase activity as well as for its interaction with PKB/Akt [21].
• Mutational analysis of ILK further shows a crucial role for arginine 211 of ILK within the phosphoinositide phospholipid binding domain in the regulation of PKB- serine 473 phosphorylation [21].
• These results indicated that ParvB inhibits ILK signaling downstream of receptor tyrosine kinases [1].
• The PINCH LIM1-2 fragment inhibited the recruitment of endogenous ILK and PINCH to integrin adhesion sites and prevented their association of ILK with beta-integrins, paxillin, and vinculin [22].

Physical interactions of ILK

• ILK is a 59 kDa protein containing a phosphoinositide phospholipid-binding domain flanked by an N-terminal ankyrin repeat domain and a C-terminal serine/threonine protein kinase domain [23].
• Integrin-linked kinase (ILK) is one of the signaling moieties that interact with the cytoplasmic domains of integrin beta1 and beta3 subunits [16].
• Furthermore, the CH2 domain alone is sufficient for FA targeting, and a point mutation that inhibits the ILK-binding impaired the FA localization of CH-ILKBP [24].
• The LIM-only protein PINCH directly interacts with integrin-linked kinase and is recruited to integrin-rich sites in spreading cells [25].
• PP2Cdelta/ILKAP also forms a complex with ILK1 to inhibit the GSK3beta-mediated integrin-ILK1 signaling in vivo, inhibiting cell cycle progression [26].

Enzymatic interactions of ILK

• Integrin-linked kinase phosphorylates the myosin phosphatase target subunit at the inhibitory site in platelet cytoskeleton [17].
• ILK also phosphorylates protein kinase B (PKB/Akt) and stimulates its activity [27].
• ILK phosphorylates GSK3 to inhibit its activity and translocates beta-catenin into the nucleus [28].

Regulatory relationships of ILK

• Integrin-linked kinase regulates vascular morphogenesis induced by vascular endothelial growth factor [16].
• In contrast to PARVA, PARVB inhibits ILK activity and reverses some of its oncogenic effects in cancer cells [29].
• We have demonstrated that ILK stimulates activator protein-1 transcriptional activity through GSK-3 and the subsequent regulation of the c-Jun-DNA interaction [27].
• In contrast, ILK-1 is ubiquitously expressed in normal tissues and is up-regulated in various tumors independent of TGF-beta 1 [30].
• ILKAP regulates ILK signaling and inhibits anchorage-independent growth [31].
• Overexpressed ILK enhanced apoptosis after irradiation by combined activation of caspase-3 through caspase-8 and -9 in irradiated FN cultures [32].

Other interactions of ILK

• Conditional knock-out of integrin-linked kinase demonstrates an essential role in protein kinase B/Akt activation [33].
• Finally, we provide evidence suggesting that inhibition of the ILK-alpha-parvin complex is sufficient, although not necessary, for promotion of apoptosis [34].
• In addition, we show that the interactions of ILK with alpha- and beta-parvin are mutually exclusive [34].
• The gamma-parvin-integrin-linked kinase complex is critically involved in leukocyte-substrate interaction [19].
• We conclude that ILK plays an important role in vascular morphogenesis mediated by VEGF [16].

Analytical, diagnostic and therapeutic context of ILK

• Immunofluorescence stainings of ILK-hk cells indicated disturbed ILK and paxillin membrane localization with concomitant decrease in focal adhesions [3].
• Co-immunoprecipitation experiments were employed to map the binding sites on ILK and actopaxin [35].
• Using mRNA from TGF-beta1 stimulated HT-144 cells and reverse transcriptase polymerase chain reaction, we have isolated a cDNA encoding a protein highly homologous to ILK [36].
• This novel finding suggests that therapies directed against ILK and its downstream signaling targets may have the potential to enhance the efficacy of gemcitabine-based chemotherapy [8].
• METHODS: The ILK messenger (m)RNA and protein expression in human mesangial cells were analysed with quantitative real-time polymerase chain reaction (PCR) and western blotting after exposure to either 100, 200, or 500 mg/dl glucose, or 100 mg/dl glucose + 400 mg/dl mannitol [37].

References