Integrin-linked kinase regulates vascular morphogenesis induced by vascular endothelial growth factor

Collagen I Microfiber Promotes Brain Capillary Network Formation in Three-Dimensional Blood-Brain Barrier Microphysiological Systems

BACKGROUND

The blood-brain barrier (BBB) strictly regulates the penetration of substances into the brain, which, although important for maintaining brain homeostasis, may delay drug development because of the difficulties in predicting pharmacokinetics/pharmacodynamics (PKPD), toxicokinetics/toxicodynamics (TKTD), toxicity, safety, and efficacy in the central nervous system (CNS). Moreover, BBB functional proteins show species differences; therefore, humanized in vitro BBB models are urgently needed to improve the predictability of preclinical studies. Recently, international trends in the 3Rs in animal experiments and the approval of the FDA Modernization Act 2.0 have accelerated the application of microphysiological systems (MPSs) in preclinical studies, and in vitro BBB models have become synonymous with BBB-MPSs. Recently, we developed an industrialized humanized BBB-MPS, BBB-NET. In our previous report, we reproduced transferrin receptor (TfR)-mediated transcytosis with high efficiency and robustness, using hydrogels including fibrin and collagen I microfibers (CMFs).

METHODS

We investigated how adding CMFs to the fibrin gel benefits BBB-NETs.

RESULTS

We showed that CMFs accelerate capillary network formation and maturation by promoting astrocyte (AC) survival, and clarified that integrin β1 is involved in the mechanism of CMFs.

CONCLUSIONS

Our data suggest that the quality control (QC) of CMFs is important for ensuring the stable production of BBB-NETs.

Efficacy and safety of intravitreal injections of conbercept for the treatment of idiopathic choroidal neovascularization

BACKGROUND

To determine the efficacy and safety of intravitreally injected conbercept, a vascular endothelial growth factor receptor fusion protein, for the treatment of idiopathic choroidal neovascularization (ICNV).

METHODS

This retrospective study analyzed outcomes in 40 patients (40 eyes) with ICNV who received intravitreal injections of conbercept 0.5 mg (0.05 ml) and were followed up for at least 12 months. All patients underwent full ophthalmic examinations, including best-corrected vision acuity (BCVA), intraocular pressure (IOP), slit-lamp examination, color fundus photography, optical coherence tomography angiography, multifocal electroretinogram, and fundus fluorescence angiography, if necessary, at baseline and after 1, 3, 6, and 12 months. BCVA, macular central retinal thickness (CRT), IOP, CNV blood flow area, thickness of the CNV-pigment epithelial detachment complex, thickness of the retinal nerve fiber layer (RNFL), and the first positive peak (P1) amplitude density in ring 1 before and after treatment were compared.

RESULTS

Mean baseline BCVA (logMAR), CRT, CNV blood flow area, and CNV-pigment epithelial detachment complex thickness were significantly lower 1, 3, 6, and 12 months after than before conbercept treatment (P < 0.05 each). IOP and baseline RNFL thickness were unaffected by conbercept treatment. P1 amplitude density was significantly higher 1, 3, 6, and 12 months after than before conbercept treatment (P < 0.05 each). None of the 40 eyes showed obvious ocular adverse reactions, such as endophthalmitis, glaucoma, cataract progression, and retinal detachment, and none of the patients experienced systemic adverse events, such as cardiovascular and cerebrovascular accidents.

CONCLUSIONS

Intravitreal injection of conbercept is beneficial to eyes with ICNV, inducing the recovery of macular structure and function and improving BCVA, while not damaging the neuroretina. Intravitreal conbercept is safe and effective for the treatment of ICNV.

Indoxyl sulfate- and P-cresol-induced monocyte adhesion and migration is mediated by integrin-linked kinase-dependent podosome formation

Cardiovascular disease is an important cause of death in patients with chronic kidney disease (CKD). Protein-bound uremic toxins, such as p-cresyl and indoxyl sulfate (IS), are poorly removed during hemodialysis, leading to vascular endothelial dysfunction and leukocyte extravasation. These processes can be related to dynamic adhesion structures called podosomes. Several studies have indicated the role of integrin-linked kinase (ILK) in the accumulation of integrin-associated proteins in podosomes. Here, we investigated the involvement of ILK and podosome formation in the adhesion and extravasation of monocytes under p-cresol (pc) and IS exposure. Incubation of THP-1 human monocyte cells with these toxins upregulated ILK kinase activity. Together, both toxins increased cell adhesion, podosome formation, extracellular matrix degradation, and migration of THP-1 cells, whereas ILK depletion with specific small interfering RNAs suppressed these processes. Interestingly, F-actin colocalized with cortactin in podosome cores, while ILK was colocalized in podosome rings under toxin stimulation. Podosome Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP) and AKT protein depletion demonstrated that monocyte adhesion depends on podosome formation and that the ILK/AKT signaling pathway is involved in these processes. Ex vivo experiments showed that both toxins induced adhesion and podosome formation in leukocytes from wild-type mice, whereas these effects were not observed in leukocytes of conditional ILK-knockdown animals. In summary, under pc and IS stimulation, monocytes increase podosome formation and transmigratory capacity through an ILK/AKT signaling pathway-dependent mechanism, which could lead to vascular injury. Therefore, ILK could be a potential therapeutic target for the treatment of vascular damage associated with CKD.

An enzyme involved in organizing structural proteins into protrusions of the cell membrane helps facilitate the movement of white blood cells that occurs in chronic kidney disease and can lead to cardiovascular damage. Laura Calleros from the University of Alcalá, Madrid, Spain, and colleagues showed how toxic metabolites that build up in the bloodstream as kidneys fail induce the activity of an enzyme called integrin-linked kinase (ILK). This enzyme in turn spurs white blood cells to form protrusions called podosomes that make the cells more mobile, enabling them to move out of blood vessels and into surrounding tissues where they can cause inflammation -mediated injury. ILK inactivation reversed these effects. Therapies that target the enzyme could therefore help limit the cardiovascular complications of chronic kidney disease.

Effects of the L-tyrosine-derived bacterial metabolite p-cresol on colonic and peripheral cells

Specific families of bacteria present within the intestinal luminal content produce p-cresol from L-tyrosine. Although the hosts do not synthesize p-cresol, they can metabolize this compound within their colonic mucosa and liver leading to the production of co-metabolites including p-cresyl sulfate (p-CS) and p-cresyl glucuronide (p-CG). p-Cresol and its co-metabolites are recovered in the circulation mainly conjugated to albumin, but also in their free forms that are excreted in the urine. An increased dietary protein intake raises the amount of p-cresol recovered in the feces and urine, while fecal excretion of p-cresol is diminished by a diet containing undigestible polysaccharides. p-Cresol in excess is genotoxic for colonocytes. In addition, in these cells, this bacterial metabolite decreases mitochondrial oxygen consumption, while increasing the anion superoxide production. In chronic kidney disease (CKD), marked accumulation of p-cresol and p-CS in plasma is measured, and in renal tubular cells, p-cresol and p-CS increase oxidative stress, affect mitochondrial function, and lead to cell death, strongly suggesting that these 2 compounds act as uremic toxins that aggravate CKD progression. p-Cresol and p-CS are also suspected to play a role in the CKD-associated adverse cardiovascular events, since they affect endothelial cell proliferation and migration, decrease the capacity of endothelial wound repair, and increase the senescence of endothelial cells. Finally, the fact that concentration of p-cresol is transiently increased in young autistic children biological fluids, and that intraperitoneal injection of p-cresol in animal models induces some behavioral characteristics observed in the autism spectrum disorders (ASD), raise the view that p-cresol may possibly represent one of the components involved in ASD etiology. Further pre-clinical and clinical studies are obviously needed to determine if the lowering of p-cresol and/or p-CS circulating concentrations, by dietary and/or pharmacological means, would allow, by itself or in combination with other interventions, to improve CKD progression and associated cardiovascular outcomes, as well as some neurological outcomes in children with an early diagnosis of autism.

Role of integrin-linked kinase in the hypoxia-induced phenotypic transition of pulmonary artery smooth muscle cells: Implications for hypoxic pulmonary hypertension

The phenotypic transition of pulmonary artery smooth muscle cells (PASMCs) from a contractile/differentiated to synthetic/de-differentiated phenotype is an important mechanism for the occurrence and development of hypoxic pulmonary hypertension (HPH). Integrin-linked kinase (ILK) is an early hypoxic response factor whose kinase activity is significantly affected during early hypoxia. Myocardin and ETS-like protein 1 (Elk-1) are co-activators of serum response factor (SRF) and can bind to SRF to mediate the phenotypic transition of PASMCs. However, little is known about the role of ILK on the phenotypic transition of these PASMCs. Thus, in our study, we explored the role of ILK in this process. We found that the expression of ILK and myocardin decreased gradually with the increase in hypoxia exposure time in the pulmonary arteries of rats. We observed that hypoxia exposure for 1 h caused an increase in the phosphorylation of Elk-1 but did not affect the expression of ILK, myocardin, or SRF. Exposure to hypoxic treatment for 1 h decreased ILK kinase activity and caused Elk-1 to suppress myocardin binding to SRF and the smooth muscle (SM) α-actin gene promoters. In addition, hypoxia exposure for 24 h decreased the expression of ILK, myocardin, SM α-actin, and calponin but increased the expression of osteopontin. Silencing of the myocardin gene significantly decreased the expression of SM α-actin and calponin but increased the expression of osteopontin. Silencing of the ILK gene significantly decreased the expression of myocardin, SM α-actin, and calponin but increased the expression of osteopontin. ILK overexpression reversed the effects of 24 h of hypoxia on the expression of myocardin, SM α-actin, calponin, and osteopontin and reversed the decrease in binding of myocardin to the SM α-actin promoter caused by 24 h of hypoxia exposure. Thus, our results suggest that ILK initiates the phenotypic transition of PASMCs. The underlying mechanism may involve hypoxia downregulating ILK kinase activity and protein expression, causing Elk-1 to compete with myocardin for binding to the SM α-actin promoter, which downregulates the expression of the downstream target myocardin and results in the phenotypic transition of PASMCs from a contractile to a synthetic phenotype. This may be an important mechanism in the development of HPH.

Systemic L-Buthionine -S-R-Sulfoximine Treatment Increases Plasma NGF and Upregulates L-cys/L-cys2 Transporter and γ-Glutamylcysteine Ligase mRNAs Through the NGF/TrkA/Akt/Nrf2 Pathway in the Striatum

Glutathione (GSH) is the most abundant intracellular antioxidant. GSH depletion leads to oxidative stress and neuronal damage in the central nervous system (CNS). In mice, the acute systemic inhibition of GSH synthesis by L-buthionine-S-R-sulfoximine (BSO) triggers a protective response and a subsequent increase in the CNS GSH content. This response might be modulated by a peripheral increment of circulating nerve growth factor (NGF). NGF is an important activator of antioxidant pathways mediated by tropomyosin-related kinase receptor A (TrkA). Here, we report that peripheral administration of BSO increased plasma NGF levels. Additionally, BSO increased NGF levels and activated the NGF/TrkA/Akt pathway in striatal neurons. Moreover, the response in the striatum included an increased transcription of nrf2, gclm, lat1, eaac1, and xct, all of which are involved in antioxidant responses, and L-cys/L-cys₂ and glutamate transporters. Using antibody against NGF confirmed that peripheral NGF activated the NGF/TrkA/Akt/Nrf2 pathway in the striatum and subsequently increased the transcription of gclm, nrf2, lat1, eaac1, and xct. These results provide evidence that the reduction of peripheral GSH pools increases peripheral NGF circulation that orchestrates a neuroprotective response in the CNS, at least in the striatum, through the NGF/TrkA/Akt/Nrf2 pathway.

Ranibizumab versus bevacizumab for the treatment of idiopathic choroidal neovascularization: 2-Year results

PURPOSE

To compare the efficacy and safety of bevacizumab vs ranibizumab for the treatment of idiopathic choroidal neovascularization (ICNV).

METHODS

This retrospective study included 60 eyes of 60 patients with ICNV who underwent intravitreal injection of bevacizumab (1.25 mg/0.05 mL, n = 30 eyes) or ranibizumab (0.5 mg/0.05 mL, n = 30 eyes). Multiple treatments were based on complete ophthalmologic investigation including slit-lamp biomicroscopy, fundus examination, fundus fluorescein angiography (FFA), optical coherence tomography (OCT), and best-corrected visual acuity (BCVA). The BCVA, central retinal thickness (CRT), intraocular pressure (IOP), FFA results, and complications were compared between the 2 groups during the 2-year follow-up.

RESULTS

Visual acuity was significantly better at 1, 3, 6, 12, and 24 months after treatment (p&lt;0.01), with no significant difference in visual acuity between the bevacizumab and ranibizumab groups. In both groups of patients, the CRT after treatment was significantly less than before. At 12 and 24 months, the CRT in the ranibizumab group was significantly less than in the bevacizumab group (p&lt;0.05). The FFA examination showed that CNV was reduced after intravitreal injection of either drug, with no significant difference in IOP between the 2 groups. No ophthalmologic or systemic complications occurred.

CONCLUSIONS

Bevacizumab and ranibizumab are effective and safe in the treatment of ICNV, with similar effects in improving visual acuity and reducing retinal edema. The long-term efficacy of ranibizumab is superior to bevacizumab in reducing CRT.

Effect of uraemia on endothelial cell damage is mediated by the integrin linked kinase pathway

KEY POINTS

Patients with chronic kidney disease have a higher risk of developing cardiovascular diseases than the general population. Their vascular endothelium is dysfunctional, among other things, because it is permanently exposed to uraemic toxins, several of which have poor clearance by conventional dialysis. Recent studies have demonstrated the important role of integrin-linked kinase (ILK) in the maintenance of endothelial integrity and in this study we investigate the involvement of ILK in the mechanism underlying vascular endothelial damage that occurs in uraemia. For the first time, we demonstrate the implication of ILK in the protection against endothelial cell damage (inhibition of proliferation, toxicity, oxidative stress and programed cell death) induced by uraemic serum from chronic kidney disease patients and uraemic toxins. This molecular mechanism may have clinical relevance because it highlights the importance of maintaining high levels of ILK activity to help preserve endothelial integrity, at least in early stages of chronic kidney disease.

ABSTRACT

Patients with chronic kidney disease (CKD) have a higher risk of developing cardiovascular diseases. Their vascular endothelium is dysfunctional, among other things, because it is permanently exposed to uraemic toxins, several of which, mostly protein-bound compounds such as indoxyl sulfate (IS) and p-cresyl sulphate, having poor clearance by conventional dialysis, induce endothelial toxicity. However, the molecular mechanism by which uraemic toxins regulate early stages of endothelial dysfunction remains unclear. Recent studies have demonstrated the important role of integrin-linked kinase (ILK) in the maintenance of endothelial integrity. In this study, we investigate the involvement of ILK in the mechanism underlying vascular endothelial damage that occurs in uraemia. First, we show that incubation of EA.hy926 cells with human uraemic serum from CKD patients upregulates ILK activity. This ILK activation also occurs when the cells are exposed to IS (25-100 μg ml(-1)), p-cresol (10-100 μg ml(-1)) or both combined, compared to human serum control. Next, we observed that high doses of both toxins together induce a slight decrease in cell proliferation and increase apoptosis and reactive oxygen species production. Interestingly, these toxic effects displayed a strong increase when the ILK protein is knocked down by small interfering RNA, even at low doses of uraemic toxins. Abrogation of AKT has demonstrated the ILK/AKT signalling pathway involved in these processes. This study has demonstrated the implication of ILK in the protection against endothelial cell damage induced by uraemic toxins, a molecular mechanism that could play a protective role in the early stages of endothelial dysfunction observed in uraemic patients.

Role of integrin-linked kinase in osteosarcoma progression

Although integrin-linked kinase (ILK) has been suggested to play a role in the tumorigenesis of a number of human epithelial carcinomas, little is known of its role in musculoskeletal sarcoma. The authors studied ILK expression by immunohistochemistry using osteosarcoma prechemotherapy specimens from 56 patients, and investigated the prognostic implications of the findings obtained. It was found that ILK overexpression was significantly correlated with the presence of distant metastasis (p = 0.008) and that it was an independent prognostic factor for both poor overall survival and poor event-free survival (p = 0.015 and 0.010, respectively). During a transfection experiment conducted by transfecting osteosarcoma cells with ILK siRNA, VEGF concentrations were measured using an ELISA kit, and then compared with those of untransfected controls to evaluate its angiogenic effects. In addition, apoptotic percentages were measured by Annexin-V flow cytometry, and invasive properties were evaluated by measuring the numbers of non-migrating cells in a Boyden chamber. It was found that ILK downregulation significantly decreased angiogenesis, increased apoptosis, and decreased invasiveness of osteosarcoma cells. These results show that ILK is a promising prognostic factor in osteosarcoma and a novel potential therapeutic target for the treatment of osteosarcoma.

Discovering the infectome of human endothelial cells challenged with Aspergillus fumigatus applying a mass spectrometry label-free approach

Blood vessel invasion is a key feature of invasive aspergillosis. This angioinvasion process contributes to tissue thrombosis, which can impair the access of leukocytes and antifungal drugs to the site of infection. It has been demonstrated that human umbilical vein endothelial cells (HUVECs) are activated and assume a prothrombotic phenotype following contact with Aspergillus fumigatus hyphae or germlings, a process that is independent of fungus viability. However, the molecular mechanisms by which this pathogen can activate endothelial cells, together with the endothelial pathways that are involved in this process, remain unknown. Using a label-free approach by High Definition Mass Spectrometry (HDMS(E)), differentially expressed proteins were identified during HUVEC-A. fumigatus interaction. Among these, 89 proteins were determined to be up- or down-regulated, and another 409 proteins were exclusive to one experimental condition: the HUVEC control or HUVEC:AF interaction. The in silico predictions provided a general view of which biological processes and/or pathways were regulated during HUVEC:AF interaction, and they mainly included cell signaling, immune response and hemostasis pathways. This work describes the first global proteomic analysis of HUVECs following interaction with A. fumigatus germlings, the fungus morphotype that represents the first step of invasion and dissemination within the host.

BIOLOGICAL SIGNIFICANCE

A. fumigatus causes the main opportunistic invasive fungal infection related to neutropenic hematologic patients. One of the key steps during the establishment of invasive aspergillosis is angioinvasion but the mechanism associated with the interaction of A. fumigatus with the vascular endothelium remains unknown. The identification of up- and down-regulated proteins expressed by human endothelial cells in response to the fungus infection can contribute to reveal the mechanism of endothelial response and, to understand the physiopathology of this high mortality disease. This article is part of a Special Issue entitled: Trends in Microbial Proteomics.

Loss of adenomatous poliposis coli-α3 integrin interaction promotes endothelial apoptosis in mice and humans

RATIONALE

Pulmonary hypertension (PH) is characterized by progressive elevation in pulmonary pressure and loss of small pulmonary arteries. As bone morphogenetic proteins promote pulmonary angiogenesis by recruiting the Wnt/β-catenin pathway, we proposed that β-catenin activation could reduce loss and induce regeneration of small pulmonary arteries (PAs) and attenuate PH.

OBJECTIVE

This study aims to establish the role of β-catenin in protecting the pulmonary endothelium and stimulating compensatory angiogenesis after injury.

METHODS AND RESULTS

To assess the impact of β-catenin activation on chronic hypoxia-induced PH, we used the adenomatous polyposis coli (Apc(Min/+)) mouse, where reduced APC causes constitutive β-catenin elevation. Surprisingly, hypoxic Apc(Min/+) mice displayed greater PH and small PA loss compared with control C57Bl6J littermates. PA endothelial cells isolated from Apc(Min/+) demonstrated reduced survival and angiogenic responses along with a profound reduction in adhesion to laminin. The mechanism involved failure of APC to interact with the cytoplasmic domain of the α3 integrin, to stabilize focal adhesions and activate integrin-linked kinase-1 and phospho Akt. We found that PA endothelial cells from lungs of patients with idiopathic PH have reduced APC expression, decreased adhesion to laminin, and impaired vascular tube formation. These defects were corrected in the cultured cells by transfection of APC.

CONCLUSIONS

We show that APC is integral to PA endothelial cells adhesion and survival and is reduced in PA endothelial cells from PH patient lungs. The data suggest that decreased APC may be a cause of increased risk or severity of PH in genetically susceptible individuals.

Silencing of the integrin-linked kinase gene induces the apoptosis in ovarian carcinoma

CONTEXT

Integrin-linked kinase (ILK), a multidomain focal adhesion protein serine/threonine kinase, plays an essential role in ovarian carcinoma. There are reports that the expression and activity of ILK are increased in ovarian cancer.

OBJECTIVE

To test the hypothesis that ILK pathway mediates the apoptosis of ovarian carcinoma SKOV3 cell influencing the cell survival, we performed these studies.

MATERIALS AND METHODS

We applied lentivirus transfection, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT), apoptotic proteins expressions assay, and Hoechst to study our hypothesis.

RESULTS

We found that silencing of the ILK increases the cell cytotoxic, growth inhibition, and apoptosis. Moreover, after blocking the activation of ILK with ILK shRNA, up-regulation of pro-apoptotic bax expression and down-regulation of the anti-apoptotic bcl-2 expression were found in ovarian cancer SKOV3 cell line. These were associated with an increasing cleaved caspase-3 activity and chromatin condensation of cell nuclear. Furthermore, the expressions of fas and fas ligand (fasL), belonging to the tumor necrosis factor family and controlling the cell apoptosis, were also enhanced.

CONCLUSIONS

Thus, these findings indicate that both the intrinsic pathway and the extrinsic death receptor pathway are involved in the process that silencing of the ILK gene induces the apoptosis in ovarian carcinoma SKOV3 cell.

Cellular repressor of E1A-stimulated genes regulates vascular endothelial cell migration by the ILK/AKT/mTOR/VEGF(165) signaling pathway

The migration of vascular endothelial cells plays a critical role in a variety of vascular physiological and pathological processes, such as embryonic development, angiogenesis, wound healing, re-endothelialization, and vascular remodeling. This study clarified the role and mechanism of a new vascular homeostasis regulator, Cellular repressor of E1A-stimulated genes (CREG), in the migration of primary human umbilical vein endothelial cells (HUVECs). A wound healing assay and transwell migration model showed that upregulation of CREG expression induced HUVEC migration and it was positively correlated with the expression of vascular endothelial growth factor. Furthermore, wild type integrin-linked kinase reversed the poor mobility of CREG knock-down HUVECs; in contrast, kinase-dead integrin-linked kinase weakened the migration of HUVECs. We also studied the effect of CREG on HUVEC migration by the addition of an mTOR inhibitor, recombinant vascular endothelial growth factor(165), neutralizing antibody of vascular endothelial growth factor(165) and AKT siRNA, and we concluded that CREG induces endothelial cell migration by activating the integrin-linked kinase/AKT/mTOR/VEGF(165) signaling pathway.

COMP-Ang1 stimulates HIF-1α-mediated SDF-1 overexpression and recovers ischemic injury through BM-derived progenitor cell recruitment

Recruitment and adhesion of bone marrow (BM)-derived circulating progenitor cells to ischemic tissue are important for vasculogenesis and tissue repair. Recently, we found cartilage oligomeric matrix protein (COMP)-Ang1 is a useful cell-priming agent to improve the therapeutic efficacy of progenitor cells. However, the effect and the underlying mechanisms of COMP-Ang1 on recruitment of BM-derived progenitor cells (BMPCs) to foci of vascular injury have not been well defined. Here, we found that COMP-Ang1 is a critical stimulator of stromal cell-derived factor 1 (SDF-1), the principal regulator of BM-cell trafficking. Furthermore, SDF-1 stimulation by COMP-Ang1 was blocked by small-interfering RNA (siRNA) against hypoxia-inducible factor-1α (HIF-1α). COMP-Ang1 increased the synthesis of HIF-1α by activating mammalian target of rapamycin (mTOR) in hypoxic endothelium. The intermediate mechanism transmitting the COMP-Ang1 signal to the downstream mTOR/HIF-1α/SDF-1 pathway was the enhanced binding of the Tie2 receptor with integrin-linked kinase (ILK), an upstream activator of mTOR. In the mouse ischemic model, local injection of COMP-Ang1 stimulated the incorporation of BMPCs into ischemic limb, thereby enhancing neovasculogenesis and limb salvage. Collectively, our findings identify the COMP-Ang1/HIF-1α/SDF-1 pathway as a novel inducer of BMPC recruitment and neovasculogenesis in ischemic disease.

Integrin-linked kinase 1: role in hormonal cancer progression

Integrin-linked kinase 1 (ILK1) is a serine/threonine kinase that plays important roles in a variety of cellular functions including cell survival, migration and angiogenesis. ILK1 is normally expressed in numerous tissues and activated by growth factors, cytokines and hormones. Dysregulation of ILK1 expression or function is found in several hormonal tumors including breast, ovary and prostate. Emerging evidence suggests that ILK overexpression promotes cellular transformation, cell survival, epithelial mesenchymal transition (EMT), and metastasis of hormonal cancer cells while inhibition of ILK1 reduces tumor growth and progression. The recent development of ILK1 inhibitors has provided novel mechanisms for blocking ILK1 signaling to curb metastasis and therapy resistance of hormonal tumors. This review will focus on recent advances made towards understanding the role of ILK signaling axis in progression of hormonal cancer.

Kindlin-2 is expressed in malignant mesothelioma and is required for tumor cell adhesion and migration

Kindlin-2 is a novel integrin-interacting focal adhesion protein that belongs to the Kindlin family. Focal adhesion proteins control cytoskeleton dynamics and promote cancer cell growth, survival, migration and metastasis. Little is known, however, about expression of Kindlin-2 in association with human cancer. We now reveal high Kindlin-2 expression in malignant mesothelioma (MM) cell lines using an affinity-purified anti-Kindlin-2 antibody. Furthermore, we show by immunohistochemistry that Kindlin-2 is highly expressed in 92 of 102 (90%) MMs with epitheliod; sarcomatoid, biphasic and poorly differentiated morphologies. In addition, Kindlin-2 expression correlates to cell proliferation, suggesting a role for Kindlin-2 in tumor growth. We also detect increased expression of Kindlin-2 at the invasion front of tumors concurrent with increased expression of integrin-linked kinase, a Kindlin-binding protein. Besides the high expression of Kindlin-2 in pleural MMs, pleural metastases of lung adenocarcinoma also express large amounts of Kindlin-2, but not Kindlin-1. Notably, in vitro, when endogenous Kindlin-2 was knocked down with RNAi in MM cells, this impaired cell spreading, adhesion and migration. Overall, our study suggests that heightened expression of Kindlin-2 might contribute to tumor progression in MM.

Expressive proteomics profile changes of injured human brain cortex due to acute brain trauma

OBJECTIVE

To find the expressive proteomics changes in damaged human brain cortex after traumatic brain injury (TBI).

METHOD

By rapid high-throughput and precise proteomic techniques, the traumatic injured human frontal cortexes were compared with non-trauma controls.

RESULTS

On 2-DE PAGE, 138 protein spots were found significantly different on expressive level of quantitative mature. Most of these proteins expressed in a fluctuant fashion within 18 hours after trauma, with mean levels lower than control. Eighty-two protein spots were identified by MALDI-MS TOF, which were products of 71 proteins and could be grouped into 10 categories based on possible functions: cytoskeleton (n = 10), metabolism (n = 13), electron transport (n = 8), signalling transduction (n = 4), stress response (n = 6), protein synthesis and turnover (n = 8), transporter (n = 5), cell cycle (n = 1), other (n = 8) and unknown (n = 9).

CONCLUSION

After traumatic brain injury, there are significant proteins expressing changes in damaged brain tissue. These proteins may play a critical role in TBI. Although some of these proteins functions are not fully understood, they may become novel biomarkers and novel therapy targets in the future.

Endothelial Cell Adhesion to the Extracellular Matrix Induces c-Src–Dependent VEGFR-3 Phosphorylation Without the Activation of the Receptor Intrinsic Kinase Activity

Rationale : Integrins cooperate with growth factor receptors to promote downstream signaling for cell proliferation and migration. However, the mechanism of receptor activation is still unknown.

Objective : To analyze the mechanism of phosphorylation of the vascular endothelial growth factor receptor (VEGFR)-3 by cell adhesion.

Methods and Results : We show that VEGFR-3 phosphorylation, induced by cell attachment to the extracellular matrix, is independent from the intrinsic kinase activity of the receptor, as evidenced from phosphorylation cell adhesion experiments with a mutant kinase dead receptor or in the presence of the specific kinase inhibitor MAZ 51. Cell adhesion experiments in the presence of the c-Src inhibitor PP2 or in fibroblast triple knockout for c-Src, Yes, and Fyn (SYF) demonstrate that VEGFR-3 phosphorylation, induced by extracellular matrix, is mediated by c-Src. Kinase assays in vitro with recombinant c-Src show that VEGFR-3 is a direct c-Src target and mass spectrometry analysis identified the sites phosphorylated by c-Src as tyrosine 830, 833, 853, 1063, 1333, and 1337, demonstrating that integrin-mediated receptor phosphorylation induces a phosphorylation pattern that is distinct from that induced by growth factors. Furthermore, pull-down assays show that integrin-mediated VEGFR-3 phosphorylation activates the recruitment to the receptor of the adaptor proteins CRKI/II and SHC inducing activation of JNK.

Conclusions : These data suggest that cell adhesion to extracellular matrix induces a downstream signaling using the tyrosine kinase receptor VEGFR-3 as scaffold.

ILK mediates LPS-induced vascular adhesion receptor expression and subsequent leucocyte trans-endothelial migration

AIMS

The inflammatory response to injurious agents is tightly regulated to avoid adverse consequences of inappropriate leucocyte accumulation or failed resolution. Lipopolysaccharide (LPS)-activated endothelium recruits leucocytes to the inflamed tissue through controlled expression of membrane-associated adhesion molecules. LPS responses in macrophages are known to be regulated by integrin-linked kinase (ILK); in this study, we investigated the role of ILK in the regulation of the LPS-elicited inflammatory response in endothelium.

METHODS AND RESULTS

This study was performed on immortalized mouse endothelial cells (EC) isolated from lung and coronary vasculature. Cells were thoroughly characterized and the role of ILK in the regulation of the LPS response was investigated by suppressing ILK expression using siRNA and shRNA technologies. Phenotypic and functional analyses confirmed that the immortalized cells behaved as true EC. LPS induced the expression of the inflammatory genes E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). ILK knockdown impaired LPS-mediated endothelial activation by preventing the induction of ICAM-1 and VCAM-1. Blockade of the LPS-induced response inhibited the inflammatory-related processes of firm adhesion and trans-endothelial migration of leucocytes.

CONCLUSION

ILK is involved in the expression of cell adhesion molecules by EC activated with the inflammatory stimulus LPS. This reduced expression modulates leucocyte adhesion to the endothelium and the extravasation process. This finding suggests ILK as a potential anti-inflammatory target for the development of vascular-specific treatments for inflammation-related diseases.

Integrin linked kinase (ILK) expression and function in vascular smooth muscle cells

Vascular smooth muscle cell (SMC) migration and proliferation contribute to arterial wound repair and thickening of the intimal layer in atherosclerosis, restenosis and transplant vascular disease. These processes are influenced by cell adhesion to molecules present in the extracellular matrix, and regulated by the integrin family of cell-surface matrix receptors. An important signaling molecule acting downstream of integrin receptors is integrin-linked kinase (ILK), a serine/threonine kinase and scaffolding protein. ILK has been implicated in cancer cell growth and survival through modulation of downstream targets, notably Akt and glycogen synthase kinase-3beta (GSK3beta). Evidence also exists to establish ILK as a molecular adaptor protein linking integrins to the actin cytoskeleton and regulating actin polymerization, and this function may not necessarily depend upon the kinase activity of ILK. ILK has been implicated in anchorage-independent growth, cell cycle progression, epithelial-mesenchymal transition (EMT), invasion and migration. In addition, ILK has been shown to be involved in vascular development, tumor angiogenesis and cardiac hypertrophy. Despite the documented involvement of integrin signaling in vascular pathologies, the function of ILK has not been well characterized in the SMC response to vascular injury. This brief review summarizes and puts into context the current literature on ILK expression and function in the vascular smooth muscle cell.

Signal co-operation between integrins and other receptor systems

The multicellular nature of metazoans means that all cellular processes need to be tuned by adhesive interactions between cells and their local microenvironment. The spatial organization of cells within tissues requires sophisticated networks of extracellular signals to control their survival and proliferation, movements and positioning, and differentiated function. These cellular characteristics are mediated by multiple inputs from adhesion systems in combination with soluble and developmental signals. In the present review we explore how one class of adhesion receptor, the integrins, co-operate with other types of receptor to control diverse aspects of cell fate. In particular we discuss: (i) how beta3 and beta1 integrins work together with growth factors to control angiogenesis; (ii) how alpha6beta4 integrin co-operates with receptor tyrosine kinases in normal epithelial function and cancer; (iii) the interplay between beta1 integrins and EGF (epidermal growth factor) receptor; (iv) signal integration connecting integrins and cytokine receptors for interleukins, prolactin and interferons; and (v) how integrins and syndecans co-operate in cell migration.

Immobilization of growth factors on collagen scaffolds mediated by polyanionic collagen mimetic peptides and its effect on endothelial cell morphogenesis

Angiogenesis, a morphogenic event endothelial cells (ECs) undergo in response to 3-D environmental triggers, is critical to the survival and ultimate functional capacity of engineered tissue constructs. Here we present a new collagen mimetic peptide (CMP) architecture consisting of multiple anionic charges at the peptide's N-terminus designed to attract growth factors by charge-charge interactions and bind to collagen by CMP-collagen interaction. The anionic CMPs exhibited specific binding affinity to type I collagen substrates while attracting vascular endothelial growth factors (VEGFs), which led to enhanced morphological features of ECs, indicative of tubulogenesis. The results show that these new CMPs could be used to direct proliferation and differentiation of cells in collagen scaffolds by localization and sustained delivery of growth factors and other morphogens.

Expression of integrin-linked kinase and its binding partners in chondrosarcoma: association with prognostic significance

Integrin-linked kinase (ILK) and its binding partners alpha-parvin, beta-parvin, Mig-2 and Migfilin are important components of the cell-matrix adhesions implicated in cell motility, growth, survival and ultimately carcinogenesis. Herein, we investigated immunohistochemically the expression of these molecules in cartilaginous neoplasms and explored their involvement in chondrosarcoma pathobiology and behaviour. Our analyses revealed that ILK, alpha-parvin, beta-parvin and Mig-2 are expressed in the majority of chondrosarcomas but in a small proportion of enchondromas, implying that these proteins might have a role in the development and progression of chondrogenic neoplasms. Moreover, our findings highlight the possibilities that ILK might serve as biological marker that could accurately predict a high-grade tumour and that Mig-2 may function as a promising prognostic indicator of high-risk patients.

Integrin-linked kinase in the vascular smooth muscle cell response to injury

Integrin-mediated interactions between smooth muscle cells (SMCs) and the extracellular matrix regulate cell migration and proliferation during neointimal hyperplasia. Integrin-linked kinase (ILK) is a serine-threonine kinase and scaffolding molecule that acts downstream of integrin receptors to modulate cell adhesion; therefore, we examined ILK function in SMCs during wound repair. Silencing of ILK expression with siRNA in vitro decreased cell adhesion to fibronectin and accelerated both cell proliferation and wound closure in the cell monolayer; it also resulted in the rearrangement of focal adhesions and diminished central actin stress fibers. Akt and GSK3beta are ILK substrates that are important in cell motility; however, ILK siRNA silencing did not attenuate injury-induced increases in Akt and GSK3beta phosphorylation. Following balloon catheter injury of the rat carotid artery in vivo, a dramatic decrease in ILK levels coincided with both the proliferation and migration of SMCs, which leads to the formation of a thickened neointima. Immunostaining revealed decreased ILK levels in the media and deep layers of the neointima, but increased ILK levels in the subluminal layers of the intima. Taken together, these results suggest that ILK functions to maintain SMC quiescence in the normal artery. A decrease in ILK levels after injury may permit SMC migration, proliferation, and neointimal thickening, and its re-expression at the luminal surface may attenuate this process during later stages of the injury response.

The vasostatin-I fragment of chromogranin A inhibits VEGF-induced endothelial cell proliferation and migration

A growing body of evidence suggests that chromogranin A (CgA), a secretory protein released by many neuroendocrine cells and frequently used as a diagnostic and prognostic serum marker for a range of neuroendocrine tumors, is a precursor of several bioactive fragments. This work was undertaken to assess whether the N-terminal fragment CgA(1-76) (called vasostatin I) can inhibit the proangiogenic activity of vascular endothelial growth factor (VEGF), a factor involved in tumor growth. The effect of recombinant human vasostatin I (VS-1) on VEGF-induced human umbilical endothelial cells (HUVEC) signaling, proliferation, migration, and organization has been investigated. We have found that VS-1 (3 microg/ml; 330 nM) can inhibit VEGF-induced ERK phosphorylation, as well as cell migration, proliferation, morphogenesis, and invasion of collagen gels in various in vitro assays. In addition, VS-1 could inhibit the formation of capillary-like structures in Matrigel plugs in a rat model. VS-1 could also inhibit basal ERK phosphorylation and motility of HUVEC, leading to a more quiescent state in the absence of VEGF, without inducing apoptotic or necrotic effects.

CONCLUSION

These findings suggest that vasostatin I may play a novel role as a regulator of endothelial cell function and homeostasis.

Integrin-linked kinase is an essential mediator for T-cadherin-dependent signaling via Akt and GSK3beta in endothelial cells

Glycosylphosphatidylinositol-anchored T-cadherin (T-cad) influences several parameters of angiogenesis including endothelial cell (EC) differentiation, migration, proliferation, and survival. This presupposes signal transduction networking via mediatory regulators and molecular adaptors since T-cad lacks transmembrane and cytosolic domains. Here, using pharmacological inhibition of PI3K, adenoviral-mediated T-cad-overexpression, siRNA-mediated T-cad-depletion, and agonistic antibody-mediated ligation, we demonstrate signaling by T-cad through PI3K-Akt-GSK3beta pathways in EC. T-cad-overexpressing EC exhibited increased levels and nuclear accumulation of active beta-catenin, which was transcriptionally active as shown by increased Lef/Tcf reporter activity and cyclin D1 levels. Cotransduction of EC with constitutively active GSK3beta (S9A-GSK3beta) abrogated the stimulatory effects of T-cad on active beta-catenin accumulation, proliferation, and survival. Integrin-linked kinase (ILK), a membrane proximal upstream regulator of Akt and GSK3beta, was considered a candidate signaling mediator for T-cad. T-cad was present in anti-ILK immunoprecipitates, and confocal microscopy revealed colocalization of T-cad and ILK within lamellipodia of migrating cells. ILK-siRNA abolished T-cad-dependent effects on (Ser-473)Akt/(Ser-9)GSK3beta phosphorylation, active beta-catenin accumulation, and survival. We conclude ILK is an essential mediator for T-cad signaling via Akt and GSK3beta in EC. This is the first demonstration that ILK can regulate inward signaling by GPI-anchored proteins. Furthermore, ILK-GSK3beta-dependent modulation of active beta-catenin levels by GPI-anchored T-cad represents a novel mechanism for controlling cellular beta-catenin activity.

Polymers for pro- and anti-angiogenic therapy

Dysregulated growth factor signaling is traditionally targeted via bolus injections of therapeutic molecules, but this approach may not recreate necessary qualitative and quantitative aspects of biologic growth factor delivery systems. Polymeric delivery systems may, instead, mimic certain sequestration and binding characteristics of the extracellular matrix and lead to the provision of therapeutic molecules at therapeutically efficient local concentrations [V], in the form of spatial gradients (d[V]/dx) and temporal gradients (d[V]/dt), and in combination with other morphogenetic cues. Both physicochemical and biological attributes dictate their design, and they may be fabricated from synthetic and natural polymers. General concepts for manipulating growth factor signaling with these systems are discussed in the context of angiogenesis with vascular endothelial growth factor (VEGF), and these strategies may be broadly adapted to a multitude of other morphogens and growth factors.

High expression of insulin-like growth factor binding protein-3 is correlated with lower portal invasion and better prognosis in human hepatocellular carcinoma

Insulin-like growth factor binding protein-3 (IGFBP-3) modulates cell proliferation of various cancer cell types. However, it remains unclear how IGF-IGFBP-3-signaling is involved in growth and progression of hepatocellular carcinoma (HCC). The aim of the present study was to evaluate the role of IGFBP-3 in HCC. Type 1 receptor for IGF (IGF-1R) was expressed at various levels in the seven lines examined, but IGF-2R was not expressed. Of the seven lines, the growth of HAK-1B, KIM-1, KYN-2 and HepG2 cells was stimulated in a dose-dependent manner by the exogenous addition of IGF-I or IGF-II, but the HAK-1A, KYN-1 and KYN-3 cell lines showed no growth. Exogenous addition of IGFBP-3 markedly blocked IGF-I and IGF-II-stimulated cell growth of KYN-2 and HepG2 cells, and moderately stimulated that of KIM-1 and HAK-1B cells, but no growth of the KYN-1, KYN-3 and HAK-1A cell lines was observed. IGF-I enhanced the phosphorylation of IGF-1R, Akt and Erk1/2 in KYN-2 cells, and coadministration of IGFBP-3 blocked all types of activation by IGF-I investigated here. In contrast, no such activation by IGF-I was detected in KYN-3 cells. IGFBP-3 also suppressed IGF-I-induced cell invasion by KYN-2 cells. Moreover, we were able to observe the apparent expression of IGFBP-3 in KYN-3 cells, but not in the other six cell lines. Furthermore reduced expression of IGFBP-3, but not that of IGF-1R, was significantly correlated with tumor size, histological differentiation, capsular invasion and portal venous invasion. Low expression of IGFBP-3 was independently associated with poor survival. IGFBP-3 could be a molecular target of intrinsic importance for further development of novel therapeutic strategy against HCC.

Akt-dependent nuclear localization of Y-box-binding protein 1 in acquisition of malignant characteristics by human ovarian cancer cells

Y-box-binding protein 1 (YB-1), which is a member of the DNA-binding protein family containing a cold-shock domain, has pleiotropic functions in response to various environmental stimuli. As we previously showed that YB-1 is a global marker of multidrug resistance in ovarian cancer and other tumor types. To identify YB-1-regulated genes in ovarian cancers, we investigated the expression profile of YB-1 small-interfering RNA (siRNA)-transfected ovarian cancer cells using a high-density oligonucleotide array. YB-1 knockdown by siRNA upregulated 344 genes, including MDR1, thymidylate synthetase, S100 calcium binding protein and cyclin B, and downregulated 534 genes, including CXCR4, N-myc downstream regulated gene 1, E-cadherin and phospholipase C. Exogenous serum addition stimulated YB-1 translocation from the cytoplasm to the nucleus, and treatment with Akt inhibitors as well as Akt siRNA and integrin-linked kinase (ILK) siRNA specifically blocked YB-1 nuclear localization. Inhibition of Akt activation downregulated CXCR4 and upregulated MDR1 (ABCB1) gene expression. Administration of Akt inhibitor resulted in decrease in nuclear YB-1-positive cancer cells in a xenograft animal model. Akt activation thus regulates the nuclear translocation of YB-1, affecting the expression of drug-resistance genes and other genes associated with the malignant characteristics in ovarian cancer cells. Therefore, the Akt pathway could be a novel target of disrupting the nuclear translocation of YB-1 that has important implications for further development of therapeutic strategy against ovarian cancers.

Integrin-linked kinase functions as a downstream mediator of endothelin-1 to promote invasive behavior in ovarian carcinoma

The endothelin-1 (ET-1) axis represents a novel target in several malignancies, including ovarian carcinoma. Upon being activated, the endothelin A receptor (ET(A)R) mediates multiple tumor-promoting activities, including mitogenesis, escape from apoptosis, angiogenesis, metastasis-related protease activation, epithelial-mesenchymal transition, and invasion. Integrin-linked kinase (ILK) is a multidomain focal adhesion protein that conveys intracellular signaling elicited by beta1-integrin and growth factor receptors. In this study, we investigate whether the signaling triggered by ET(A)R leading to an aggressive phenotype is mediated by an ILK-dependent mechanism. In HEY and OVCA 433 ovarian carcinoma cell lines, activation of ET(A)R by ET-1 enhances the expression of alpha2beta1 and alpha3beta1 integrins. ILK activity increases as ovarian cancer cells adhere to type I collagen through beta1 integrin signaling, and do so to a greater extent on ET-1 stimulation. ET-1 increases ILK mRNA and protein expression and activity in a time- and concentration-dependent manner. An ILK small-molecule inhibitor (KP-392) or transfection with a dominant-negative ILK mutant effectively blocks the phosphorylation of downstream signals, Akt and glycogen synthase kinase-3beta. The blockade of ET-1/ET(A)R-induced ILK activity results in an inhibition of matrix metalloproteinase activation as well as of cell motility and invasiveness in a phosphoinositide 3 kinase-dependent manner. 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. These data show that ILK functions as a downstream mediator of the ET-1/ET(A)R axis to potentiate aggressive cellular behavior. Thus, the ILK-related signaling cascade can be efficiently targeted by pharmacologic blockade of ET(A)R.

Involvement of integrin-linked kinase in carbon tetrachloride-induced hepatic fibrosis in rats

Integrin-linked kinase (ILK) is a multidomain focal adhesion protein implicated in signal transduction between integrins and growth factor receptors. Although its expression is upregulated in pulmonary and renal fibrosis, its role in the development of hepatic fibrosis remains to be determined. Therefore, we considered it important to investigate whether ILK is involved in activation of hepatic stellate cells and thus plays a role in the development of hepatic fibrosis. Immunohistochemical analysis of liver sections obtained from rats with CCl4-induced cirrhosis revealed increased expression and colocalization of ILK and alpha-smooth muscle actin in hepatic stellate cells in perisinusoidal areas. In addition, hepatic stellate cells isolated from fibrotic livers expressed high levels of ILK and alpha-smooth muscle actin, and their expression was sustained in culture. In contrast, hepatic stellate cells (HSCs) isolated from normal rat liver did not express ILK, but its expression was increased when the cells were activated in culture. Our studies also showed that ILK is involved in the phosphorylation of ERK 1/2, p38 MAPK, JNK, and PKB and that selective inhibition of ILK expression by siRNA results in a significant decrease in their phosphorylation. These changes were accompanied by significant inhibition of cell spreading and migration without affecting cell proliferation. In conclusion, ILK plays a key role in HSC activation and could be a possible target for antifibrogenic therapy.

Vascular endothelial growth factor in the lung

Vascular endothelial growth factor (VEGF) is a pluripotent growth and permeability factor that has a broad impact on endothelial cell function. The lung tissue is very rich in this protein; many different lung cells produce VEGF and also respond to VEGF. VEGF is critical for the development of the lung and serves as a maintenance factor during adult life. In addition to the physiological functions of this protein, there is increasing evidence that VEGF also plays a role in several acute and chronic lung diseases, such as acute lung injury, severe pulmonary hypertension, and emphysema. Here we provide a comprehensive overview of the rapidly expanding literature.

Peptides Derived from Human Decorin Leucine-rich Repeat 5 Inhibit Angiogenesis

Excessive angiogenesis is involved in many human diseases, and inhibiting angiogenesis is an important area of drug development. There have been conflicting reports as to whether decorin could function as an angiogenic inhibitor when used as an extracellular soluble factor. In this study, we demonstrated that not only purified decorin but also the 26-residue leucine-rich repeat 5 (LRR5) of decorin core protein functions as angiogenesis inhibitor by inhibiting both vascular endothelial growth factor (VEGF) and basic fibroblast growth factor-induced angiogenesis. Peptide LRR5 inhibited angiogenesis through multiple mechanisms, including inhibiting VEGF-stimulated endothelial cell (EC) migration, tube formation on Matrigel, cell attachment to fibronectin, as well as induction of EC apoptosis without significantly affecting their proliferation. We further demonstrated that different subregions of LRR5 inhibited different aspects of angiogenesis, with the middle region (LRR5M, 12 residues) inhibiting endothelial cell tube formation up to 1000 times more potently than LRR5. Although the C-terminal region (LRR5C) potently inhibited VEGF-stimulated endothelial cell migration, the N-terminal region (LRR5N) is as active as LRR5 in inhibiting endothelial cell attachment to fibronectin. Although both LRR5M and LRR5N induced EC apoptosis dose-dependently similar to LRR5 through a caspase-dependent pathway, LRR5C has no such function. We further showed that the inhibition of tube formation by LRR5 and LRR5M is linked with their ability to suppress VEGF-induced focal adhesion kinase phosphorylation and the assembly of focal adhesions and actin stress fibers in ECs, but not their ability to interfere with endothelial cell attachment to the matrix. Circular dichroism studies revealed that LRR5 undergoes an inter-conversion between 3(10) helix and beta-sheet structure in solution, a characteristic potentially important for its anti-angiogenic activity. Peptide LRR5 and its derivatives are therefore novel angiogenesis inhibitors that may serve as prototypes for further development into anti-angiogenic drugs.

Integrin-linked kinase mediates bone morphogenetic protein 7-dependent renal epithelial cell morphogenesis

Bone morphogenetic protein 7 (BMP7) stimulates renal branching morphogenesis via p38 mitogen-activated protein kinase (p38(MAPK)) and activating transcription factor 2 (ATF-2) (M. C. Hu, D. Wasserman, S. Hartwig, and N. D. Rosenblum, J. Biol. Chem. 279:12051-12059, 2004). Here, we demonstrate a novel role for integrin-linked kinase (ILK) in mediating renal epithelial cell morphogenesis in embryonic kidney explants and identify p38(MAPK) as a target of ILK signaling in a cell culture model of renal epithelial morphogenesis. The spatial and temporal expression of ILK in embryonic mouse kidney cells suggested a role in branching morphogenesis. Adenovirus-mediated expression of ILK stimulated and expression of a dominant negative ILK mutant inhibited ureteric bud branching in embryonic mouse kidney explants. BMP7 increased ILK kinase activity in inner medullary collecting duct 3 (IMCD-3) cells, and adenovirus-mediated expression of ILK increased IMCD-3 cell morphogenesis in a three-dimensional culture model. In contrast, treatment with a small molecule ILK inhibitor or expression of a dominant negative-acting ILK (ILK(E359K)) inhibited epithelial cell morphogenesis. Further, expression of ILK(E359K) abrogated BMP7-dependent stimulation. To investigate the role of ILK in BMP7 signaling, we showed that ILK overexpression increased basal and BMP7-induced levels of phospho-p38(MAPK) and phospho-ATF-2. Consistent with its inhibitory effects on IMCD-3 cell morphogenesis, expression of ILK(E359K) blocked BMP7-dependent increases in phospho-p38(MAPK) and phospho-ATF-2. Inhibition of p38(MAPK) activity with the specific inhibitor, SB203580, failed to inhibit BMP7-dependent stimulation of ILK activity, suggesting that ILK functions upstream of p38(MAPK) during BMP7 signaling. We conclude that ILK functions in a BMP7/p38(MAPK)/ATF-2 signaling pathway and stimulates epithelial cell morphogenesis.

Involvement of integrin-linked kinase in capillary/tube-like network formation of human vascular endothelial cells

Angiogenesis is a complex process involving an ECM and vascular endothelial cells (EC), and is regulated by various angiogenic factors including VEGF. The ability to form a capillary/tube-like network is a specialized function of EC. Therefore, in vitro angiogenesis was assessed by a capillary/tube-like network formation assay. There are three angiogenic parameters: capillary length, number of capillaries, and relative capillary area per field. We evaluated capillary length per field in the assay. VEGF promoted capillary/tube-like network formation of EC in a type I collagen gel matrix in vitro. Moreover, we demonstrated the involvement of ILK in a VEGF signaling pathway mediating capillary/tube-like network formation of EC using dominant-negative, kinase deficient ILK. This is a straightforward assay to monitor responses of human vascular endothelial cells.

Assembly and Signaling of Adhesion Complexes

Cell-extracellular matrix (ECM) adhesion is crucial for control of cell behavior. It connects the ECM to the intracellular cytoskeleton and transduces bidirectional signals between the extracellular and intracellular compartments. The subcellular machinery that mediates cell-ECM adhesion and signaling is complex. It consists of transmembrane proteins (e.g., integrins) and at least several dozens of membrane-proximal proteins that assemble into a network through multiple protein interactions. Furthermore, despite sharing certain common components, cell-ECM adhesions exhibit considerable heterogeneity in different types of cells (e.g., the cell-ECM adhesions in cardiac myocytes are considerably different from those in fibroblasts). Here, we will first briefly describe the general properties of the integrin-mediated cell-ECM adhesion and signal transduction. Next, we will focus on one of the recently discovered cell-ECM adhesion protein complexes consisting of PINCH, integrin-linked kinase (ILK), and Parvin and use it as an example to illustrate the molecular basis underlying the assembly and functions of cell-ECM adhesions. Finally, we will discuss in detail the structure and regulation of cell-ECM adhesion complexes in cardiac myocytes, which illustrate the importance and complexity of the cell-ECM adhesion structures in organogenesis and diseases.

Integrin-linked kinase: a cancer therapeutic target unique among its ILK

Cancer development requires the acquisition of several capabilities that include increased replicative potential, anchorage and growth-factor independence, evasion of apoptosis, angiogenesis, invasion of surrounding tissues and metastasis. One protein that has emerged as promoting many of these phenotypes when dysregulated is integrin-linked kinase (ILK), a unique intracellular adaptor and kinase that links the cell-adhesion receptors, integrins and growth factors to the actin cytoskeleton and to a range of signalling pathways. The recent findings of increased levels of ILK in various cancers, and that inhibition of ILK expression and activity is antitumorigenic, makes ILK an attractive target for cancer therapeutics.