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

Adiponectin suppresses stiffness-dependent, profibrotic activation of lung fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible respiratory disease with limited therapeutic options. A hallmark of IPF is excessive fibroblast activation and extracellular matrix (ECM) deposition. The resulting increase in tissue stiffness amplifies fibroblast activation and drives disease progression. Dampening stiffness-dependent activation of fibroblasts could slow disease progression. We performed an unbiased, next-generation sequencing (NGS) screen to identify signaling pathways involved in stiffness-dependent lung fibroblast activation. Adipocytokine signaling was downregulated in primary lung fibroblasts (PFs) cultured on stiff matrices. Re-activating adipocytokine signaling with adiponectin suppressed stiffness-dependent activation of human PFs. Adiponectin signaling depended on CDH13 expression and p38 mitogen-activated protein kinase gamma (p38MAPKγ) activation. CDH13 expression and p38MAPKγ activation were strongly reduced in lungs from IPF donors. Our data suggest that adiponectin-signaling via CDH13 and p38MAPKγ activation suppresses profibrotic activation of fibroblasts in the lung. Targeting of the adiponectin signaling cascade may provide therapeutic benefits in IPF.NEW & NOTEWORTHY A hallmark of idiopathic pulmonary fibrosis (IPF) is excessive fibroblast activation and extracellular matrix (ECM) deposition. The resulting increase in tissue stiffness amplifies fibroblast activation and drives disease progression. Dampening stiffness-dependent activation of fibroblasts could slow disease progression. We found that activation of the adipocytokine signaling pathway halts and reverses stiffness-induced, profibrotic fibroblast activation. Specific targeting of this signaling cascade may therefore provide therapeutic benefits in IPF.

T-cadherin is a novel regulator of pericyte function during angiogenesis

Pericytes are mural cells that play an important role in regulation of angiogenesis and endothelial function. Cadherins are a superfamily of adhesion molecules mediating Ca²⁺-dependent homophilic cell-cell interactions that control morphogenesis and tissue remodeling. To date, classical N-cadherin is the only cadherin described on pericytes. Here, we demonstrate that pericytes also express T-cadherin (H-cadherin, CDH13), an atypical glycosyl-phosphatidylinositol (GPI)-anchored member of the superfamily that has previously been implicated in regulation of neurite guidance, endothelial angiogenic behavior, and smooth muscle cell differentiation and progression of cardiovascular disease. The aim of the study was to investigate T-cadherin function in pericytes. Expression of T-cadherin in pericytes from different tissues was performed by immunofluorescence analysis. Using lentivirus-mediated gain-of-function and loss-of-function in cultured human pericytes, we demonstrate that T-cadherin regulates pericyte proliferation, migration, invasion, and interactions with endothelial cells during angiogenesis in vitro and in vivo. T-cadherin effects are associated with the reorganization of the cytoskeleton, modulation of cyclin D1, α-smooth muscle actin (αSMA), integrin β3, metalloprotease MMP1, and collagen expression levels, and involve Akt/GSK3β and ROCK intracellular signaling pathways. We also report the development of a novel multiwell 3-D microchannel slide for easy analysis of sprouting angiogenesis from a bioengineered microvessel in vitro. In conclusion, our data identify T-cadherin as a novel regulator of pericyte function and support that it is required for pericyte proliferation and invasion during active phase of angiogenesis, while T-cadherin loss shifts pericytes toward the myofibroblast state rendering them unable to control endothelial angiogenic behavior.

Protozoan phagotrophy from predators to parasites: An overview of the enigmatic cytostome-cytopharynx complex of Trypanosoma cruzi

Eating is fundamental and from this basic principle, living organisms have evolved innumerable strategies to capture energy and nutrients from their environment. As part of the world's aquatic ecosystems, the expansive family of heterotrophic protozoans uses self-generated currents to funnel prokaryotic prey into an ancient, yet highly enigmatic, oral apparatus known as the cytostome-cytopharynx complex prior to digestion. Despite its near ubiquitous presence in protozoans, little is known mechanistically about how this feeding organelle functions. Intriguingly, one class of these flagellated phagotrophic predators known as the kinetoplastids gave rise to a lineage of obligate parasitic protozoa, the trypanosomatids, that can infect a wide variety of organisms ranging from plants to humans. One parasitic species of humans, Trypanosoma cruzi, has retained this ancestral organelle much like its free-living relatives and continues to use it as its primary mode of endocytosis. In this review, we will highlight foundational observations made regarding the cytostome-cytopharynx complex and examine some of the most pressing questions regarding the mechanistic basis for its function. We propose that T. cruzi has the potential to serve as an excellent model system to dissect the enigmatic process of protozoal phagotrophy and thus enhance our overall understanding of fundamental eukaryotic biology.

New Perspectives on the Role of Integrin-Linked Kinase (ILK) Signaling in Cancer Metastasis

Simple Summary

Today, the vast majority of deaths from cancer are due to cancer metastasis. Metastasis requires that cancer cells escape from the initial tumor, travel through blood vessels, and form new tumors in distant host tissues. Integrin-linked kinase (ILK) is overexpressed by many types of cancer cells and provides both structural and signaling functions that are important for successful metastasis. Here, we discuss recent findings that show how ILK is involved in promoting physical changes important for cell motility and invasion, and how ILK relays signals to other machinery components during metastasis, including interactions with components of the immune system and communication between cancer cells and normal cells, to affect the process of metastasis. We also discuss the contribution of ILK to therapeutic resistance and examine efforts to target ILK for the treatment of metastatic disease.

Abstract

Cancer metastasis is a major barrier to the long-term survival of cancer patients. In cancer cells, integrin engagement downstream of cell-extracellular matrix (ECM) interactions results in the recruitment of cytoskeletal and signaling molecules to form multi-protein complexes to promote processes critical for metastasis. One of the major functional components of these complexes is Integrin Linked Kinase (ILK). Here, we discuss recent advances in our understanding of the importance of ILK as a signaling effector in processes linked to tumor progression and metastasis. New mechanistic insights as to the role of ILK in cellular plasticity, epithelial mesenchymal transition (EMT), migration, and invasion, including the impact of ILK on the formation of invadopodia, filopodia-like protrusions (FLPs), and Neutrophil Extracellular Trap (NET)-induced motility are highlighted. Recent findings detailing the contribution of ILK to therapeutic resistance and the importance of ILK as a potentially therapeutically tractable vulnerability in both solid tumors and hematologic malignancies are discussed. Indeed, pharmacologic inhibition of ILK activity using specific small molecule inhibitors is effective in curtailing the contribution of ILK to these processes, potentially offering a novel therapeutic avenue for inhibiting critical steps in the metastatic cascade leading to reduced drug resistance and increased therapeutic efficacy.

Cadherin-13 is a critical regulator of GABAergic modulation in human stem-cell-derived neuronal networks

Activity in the healthy brain relies on a concerted interplay of excitation (E) and inhibition (I) via balanced synaptic communication between glutamatergic and GABAergic neurons. A growing number of studies imply that disruption of this E/I balance is a commonality in many brain disorders; however, obtaining mechanistic insight into these disruptions, with translational value for the patient, has typically been hampered by methodological limitations. Cadherin-13 (CDH13) has been associated with autism and attention-deficit/hyperactivity disorder. CDH13 localizes at inhibitory presynapses, specifically of parvalbumin (PV) and somatostatin (SST) expressing GABAergic neurons. However, the mechanism by which CDH13 regulates the function of inhibitory synapses in human neurons remains unknown. Starting from human-induced pluripotent stem cells, we established a robust method to generate a homogenous population of SST and MEF2C (PV-precursor marker protein) expressing GABAergic neurons (iGABA) in vitro, and co-cultured these with glutamatergic neurons at defined E/I ratios on micro-electrode arrays. We identified functional network parameters that are most reliably affected by GABAergic modulation as such, and through alterations of E/I balance by reduced expression of CDH13 in iGABAs. We found that CDH13 deficiency in iGABAs decreased E/I balance by means of increased inhibition. Moreover, CDH13 interacts with Integrin-β1 and Integrin-β3, which play opposite roles in the regulation of inhibitory synaptic strength via this interaction. Taken together, this model allows for standardized investigation of the E/I balance in a human neuronal background and can be deployed to dissect the cell-type-specific contribution of disease genes to the E/I balance.

T-cadherin inhibits invasion and migration of endometrial stromal cells in endometriosis

STUDY QUESTION

What is the expression level of T-cadherin in endometriosis, and does T-cadherin play a role in regulating invasion and migration of endometrial stromal cells?

SUMMARY ANSWER

T-cadherin expression was reduced in ectopic endometriotic lesions compared to eutopic endometrium, and T-cadherin overexpression inhibited the invasion and migration of endometrial stromal cells.

WHAT IS KNOWN ALREADY

Endometriosis is a disease that involves active cell invasion and migration. T-cadherin can inhibit cell invasion, migration and proliferation in various cancer cells, but its role in endometriosis has not been investigated.

STUDY DESIGN, SIZE, DURATION

We explored the expression status of T-cadherin in 40 patients with and 24 without endometriosis. We also isolated endometrial stromal cells to study the invasion, migration and signaling pathway regulation of T-cadherin overexpression.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients were recruited at the Guangzhou Women and Children's Medical Center to study the expression levels of T-cadherin. The expression of T-cadherin was detected by immunohistochemistry staining and western blot. H-score was used to evaluate the staining intensity of T-cadherin. The correlation between T-cadherin expression levels (H-score) and endometriosis patients' age, stage, lesion size and adhesion was analyzed. Endometrial stromal cells from patients with and without endometriosis were isolated, and cell invasion and migration were detected by transwell assays after T-cadherin overexpression. The expression of vimentin in T-cadherin-overexpressed cells was detected by western blot. After T-cadherin overexpression, the phosphorylation profile of signaling pathway proteins was detected with the Proteome Profiler Human Phospho-Kinase Array Kit.

MAIN RESULTS AND THE ROLE OF CHANCE

There was no difference in the expression of T-cadherin in the normal endometrium of control patients and the eutopic endometrium of endometriotic patients, but it was significantly decreased in the ectopic endometrium of endometriotic patients, compared with control endometrium and eutopic endometrium of endometriosis patients (P < 0.0001, for both). Western blot analysis also showed that the expression of T-cadherin was decreased in ectopic endometriotic lesions, but not the normal control endometrium or the endometriotic eutopic endometrium. The results of transwell assays indicated that T-cadherin overexpression inhibited the invasion and migration of endometrial stromal cells. In addition, T-cadherin overexpression promoted the phosphorylation of HSP27 (S78/S82) and JNK 1/2/3 (T183/Y185, T221/Y223) and decreased the expression of vimentin, MMP2 and MMP9 in eutopic endometriosis stromal cells.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The control group were patients with benign gynecological conditions (e.g. uterus myoma, endometrial or cervical polyp), which may have genetic or epigenetic variations associated with T-cadherin expression and signaling pathways. The case numbers of involved endometriosis and control patients were limited. This study only used endometrial stromal cells from patients with or without endometriosis. Ideally, ectopic endometrial stromal cells of the ovarian endometriotic lesions should also be utilized to explore the function of T-cadherin.

WIDER IMPLICATIONS OF THE FINDINGS

Further investigation of the role of T-cadherin in endometriosis may generate new potential therapeutic targets for this complex disorder.

STUDY FUNDING AND COMPETING INTEREST(S)

This study was supported by the Natural Science Foundation of Guangdong Province (2016A030313495), National Natural Science Foundation of China (81702567, 81671406, 31871412), the Science and Technology Programs of Guangdong (2017A050501021), Medical Science Technology Research Fund of Guangdong Province (A2018075), the Science and Technology Programs of Guangzhou City (201704030103), Internal Project of Family Planning Research Institute of Guangdong Province (S2018004), Post-doc initiation fund of Guangzhou (3302) and Post-doc science research initiation fund of Guangzhou Women and Children's Medical Center (20160322). There are no conflicts of interest.

Pleiotropic role of prokineticin 1 in the porcine endometrium during pregnancy establishment and embryo implantation †

Acquisition of endometrial receptivity for embryo implantation is one of the crucial processes during pregnancy and is induced mainly by progesterone and enhanced by conceptus signals. Prokineticin 1 (PROK1) is characterized as a secretory protein with diverse functions in various tissues, including the reproductive tract. PROK1, with its receptor PROKR1, are up-regulated in the porcine endometrium during implantation and in women's receptive endometrium and decidua. However, the function of PROK1 in embryo-maternal communication has still not been fully elucidated. Hence, we hypothesize that PROK1 is involved in endometrial receptivity development and implantation in pigs. In this study, using the porcine in vivo model of intrauterine infusions of estradiol-17β (E2) and prostaglandin E2 (PGE2), we revealed that these hormones elevated endometrial expression of PROK1 and PROKR1 mRNA, respectively. Moreover, E2, acting synergistically with PGE2, increased PROKR1 protein expression. We also evidenced that PROK1-PROKR1 signaling induced expression of following genes and/or proteins CCN2, CDH13, FGF2, NFATC2, ANGPT1, ANGPT2, CDH1, MUC4, SPP1, IFNG, IL6, LIF, LIFR, TNF, TGFB3, and FGF9, as well as phosphorylation of PTK2 and secretion of IL6 and IL11 by endometrial explants in vitro. Ingenuity pathway analysis revealed that functions associated with the PROK1-regulated genes/proteins include cell-to-cell contact, cell attachment, migration and viability, differentiation of epithelial tissue, leukocyte migration, inflammatory response, angiogenesis, and vasculogenesis. Summarizing, our study suggests that PROK1 acts pleiotropically as an embryonic signal mediator that regulates endometrial receptivity by increasing the expression of the genes and proteins involved in implantation and pregnancy establishment in pigs.

Protective role of Cadherin 13 in interneuron development

Cortical interneurons are generated in the ganglionic eminences and migrate through the ventral and dorsal telencephalon before finding their final positions within the cortical plate. During early stages of migration, these cells are present in two well-defined streams within the developing cortex. In an attempt to identify candidate genes which may play a role in interneuron stream specification, we previously carried out a microarray analysis which identified a number of cadherin receptors that were differentially expressed in these streams, including Cadherin-13 (Cdh13). Expression analysis confirmed Cdh13 to be present in the preplate layer at E13.5 and, later in development, in some cortical interneurons and pyramidal cells. Analysis of Cdh13 knockout mice at E18.5, but not at E15.5, showed a reduction in the number of interneurons and late born pyramidal neurons and a concomitant increase in apoptotic cells in the cortex. These observations were confirmed in dissociated cell cultures using overexpression and short interfering RNAs (siRNAs) constructs and dominant negative inhibitory proteins. Our findings identified a novel protective role for Cdh13 in cortical neuron development.

T-cadherin deficiency increases vascular vulnerability in T2DM through impaired NO bioactivity

Background

Endothelial dysfunction plays a critical role in the development of type 2 diabetes (T2DM). T-cadherin (T-cad) has gained recognition as a regulator of endothelial cell (EC) function. The present study examined whether T-cad deficiency increases vascular vulnerability in T2DM.

Methods

Vascular segments were isolated from WT or T-cad knockout mice. Endothelial function, total NO accumulation, and the expression of T-cad related proteins were determined.

Results

Ach and acidified NaNO2 induced similar vasorelaxation in WT groups. T-cad KO mice exhibited normal response to acidified NaNO2, but manifested markedly reduced response to Ach. NO accumulation was also decreased in T-cad KO group. T-cad expression was reduced in WT mice fed 8 weeks of high fat diet (HFD). Furthermore, exacerbated reduction of vasorelaxation was observed in T-cad KO mice fed 8 weeks of HFD.

Conclusions

In the current study, we provide the first in vivo evidence that T-cadherin deficiency causes endothelial dysfunction in T2DM vascular segments, suggesting the involvement of T-cad deficiency in T2DM pathogenesis.

Adiponectin association with T-cadherin protects against neointima proliferation and atherosclerosis

Adiponectin, an adipocyte-derived protein abundant in the circulation, is thought to be protective against atherosclerosis. However, it is not fully understood how the association of adiponectin with vascular cells and its antiatherogenic effect are connected. In this study, T-cadherin was essential for accumulation of adiponectin in the neointima and atherosclerotic plaque lesions, and the adiponectin-T-cadherin association protected against vascular injury. In the apolipoprotein E-knockout (ApoE-KO) mice, adiponectin and T-cadherin colocalized on endothelial cells and synthetic smooth muscle cells in the aortic intima. Notably, aortic adiponectin protein disappeared in T-cadherin/ApoE double-knockout (Tcad/ApoE-DKO) mice with significant elevation of blood adiponectin concentration. Furthermore, in Tcad/ApoE-DKO mice, carotid artery ligation resulted in a significant increase of neointimal thickness compared with ApoE-KO mice. Finally, on a high-cholesterol diet, Tcad/ApoE-DKO mice increased atherosclerotic plaque formation, despite a 5-fold increase in plasma adiponectin level compared with that in ApoE-KO mice. In vitro, knockdown of T-cadherin from human aortic smooth muscle cells (HASMCs) with synthetic phenotype significantly reduced adiponectin accumulation on HASMCs and negated the inhibitory effect of adiponectin on proinflammatory change. Collective evidence showed that adiponectin accumulates in the vasculature via T-cadherin, and the adiponectin-T-cadherin association plays a protective role against neointimal and atherosclerotic plaque formations.-Fujishima, Y., Maeda, N., Matsuda, K., Masuda, S., Mori, T., Fukuda, S., Sekimoto, R., Yamaoka, M., Obata, Y., Kita, S., Nishizawa, H., Funahashi, T., Ranscht, B., Shimomura, I. Adiponectin association with T-cadherin protects against neointima proliferation and atherosclerosis.

Cadherin-13, a risk gene for ADHD and comorbid disorders, impacts GABAergic function in hippocampus and cognition

Cadherin-13 (CDH13), a unique glycosylphosphatidylinositol-anchored member of the cadherin family of cell adhesion molecules, has been identified as a risk gene for attention-deficit/hyperactivity disorder (ADHD) and various comorbid neurodevelopmental and psychiatric conditions, including depression, substance abuse, autism spectrum disorder and violent behavior, while the mechanism whereby CDH13 dysfunction influences pathogenesis of neuropsychiatric disorders remains elusive. Here we explored the potential role of CDH13 in the inhibitory modulation of brain activity by investigating synaptic function of GABAergic interneurons. Cellular and subcellular distribution of CDH13 was analyzed in the murine hippocampus and a mouse model with a targeted inactivation of Cdh13 was generated to evaluate how CDH13 modulates synaptic activity of hippocampal interneurons and behavioral domains related to psychopathologic (endo)phenotypes. We show that CDH13 expression in the cornu ammonis (CA) region of the hippocampus is confined to distinct classes of interneurons. Specifically, CDH13 is expressed by numerous parvalbumin and somatostatin-expressing interneurons located in the stratum oriens, where it localizes to both the soma and the presynaptic compartment. Cdh13(-/-) mice show an increase in basal inhibitory, but not excitatory, synaptic transmission in CA1 pyramidal neurons. Associated with these alterations in hippocampal function, Cdh13(-/-) mice display deficits in learning and memory. Taken together, our results indicate that CDH13 is a negative regulator of inhibitory synapses in the hippocampus, and provide insights into how CDH13 dysfunction may contribute to the excitatory/inhibitory imbalance observed in neurodevelopmental disorders, such as ADHD and autism.

HANAC Syndrome Col4a1 Mutation Causes Neonate Glomerular Hyperpermeability and Adult Glomerulocystic Kidney Disease

Hereditary angiopathy, nephropathy, aneurysms, and muscle cramps (HANAC) syndrome is an autosomal dominant syndrome caused by mutations in COL4A1 that encodes the α1 chain of collagen IV, a major component of basement membranes. Patients present with cerebral small vessel disease, retinal tortuosity, muscle cramps, and kidney disease consisting of multiple renal cysts, chronic kidney failure, and sometimes hematuria. Mutations producing HANAC syndrome localize within the integrin binding site containing CB3[IV] fragment of the COL4A1 protein. To investigate the pathophysiology of HANAC syndrome, we generated mice harboring the Col4a1 p.Gly498Val mutation identified in a family with the syndrome. Col4a1 G498V mutation resulted in delayed glomerulogenesis and podocyte differentiation without reduction of nephron number, causing albuminuria and hematuria in newborns. The glomerular defects resolved within the first month, but glomerular cysts developed in 3-month-old mutant mice. Abnormal structure of Bowman's capsule was associated with metalloproteinase induction and activation of the glomerular parietal epithelial cells that abnormally expressed CD44,α-SMA, ILK, and DDR1. Inflammatory infiltrates were observed around glomeruli and arterioles. Homozygous Col4a1 G498V mutant mice additionally showed dysmorphic papillae and urinary concentration defects. These results reveal a developmental role for the α1α1α2 collagen IV molecule in the embryonic glomerular basement membrane, affecting podocyte differentiation. The observed association between molecular alteration of the collagenous network in Bowman's capsule of the mature kidney and activation of parietal epithelial cells, matrix remodeling, and inflammation may account for glomerular cyst development and CKD in patients with COL4A1-related disorders.

Using Pharmacokinetic Profiles and Digital Quantification of Stained Tissue Microarrays as a Medium-Throughput, Quantitative Method for Measuring the Kinetics of Early Signaling Changes Following Integrin-Linked Kinase Inhibition in an In Vivo Model of Cancer

A small molecule inhibitor (QLT0267) targeting integrin-linked kinase is able to slow breast tumor growth in vivo; however, the mechanism of action remains unknown. Understanding how targeting molecules involved in intersecting signaling pathways impact disease is challenging. To facilitate this understanding, we used tumor tissue microarrays (TMA) and digital image analysis for quantification of immunohistochemistry (IHC) in order to investigate how QLT0267 affects signaling pathways in an orthotopic model of breast cancer over time. Female NCR nude mice were inoculated with luciferase-positive human breast tumor cells (LCC6^Luc) and tumor growth was assessed by bioluminescent imaging (BLI). The plasma levels of QLT0267 were determined by LC-MS/MS methods following oral dosing of QLT0267 (200 mg/kg). A TMA was constructed using tumor tissue collected at 2, 4, 6, 24, 78 and 168 hr after treatment. IHC methods were used to assess changes in ILK-related signaling. The TMA was digitized, and Aperio ScanScope and ImageScope software were used to provide semi-quantitative assessments of staining levels. Using medium-throughput IHC quantitation, we show that ILK targeting by QLT0267 in vivo influences tumor physiology through transient changes in pathways involving AKT, GSK-3 and TWIST accompanied by the translocation of the pro-apoptotic protein BAD and an increase in Caspase-3 activity.

Association between the expression of T-cadherin and vascular endothelial growth factor and the prognosis of patients with gastric cancer

T-cadherin has been identified as a tumor-suppressor gene in several types of cancer. The present study aimed to investigate the association of the expression of T-cadherin with angiogenesis, and to evaluate its prognostic value for patients with primary gastric cancer. Gastric cancer tissues and matched adjacent tissues from 166 patients receiving surgical resection were included in the present study. The expression of T-cadherin was detected using immunohistochemistry, western blotting and reverse transcription-quantitative polymerase chain reaction. The expression of vascular epidermal growth factor (VEGF) was detected using immunohistochemistry, and its association with the expression of T-cadherin was analyzed. In addition, the association between the expression of T-cadherin and clinicopathological features were analyzed. The mRNA and protein expression levels of T-cadherin were significantly lower in the gastric cancer tissue compared with the corresponding adjacent normal tissue (P<0.05). The expression of VEGF was not associated with the expression of T-cadherin in the gastric cancer tissue. The decreased protein expression of T-cadherin correlated with smoking, larger tumor size (diameter, >4 cm), lymph node metastasis and a higher tumor-lymph node-metastasis stage (P<0.05 or P<0.01). However, the expression of T-cadherin was not correlated with gender, age, alcohol intake, Helecobacter pylori infection or differentiation (P>0.05). The multivariate analysis demonstrated that the expression of T-cadherin was an independent prognostic factor for the overall survival rate of patients with gastric cancer. This data suggested that the downregulation of T-cadherin may contribute to gastric cancer progression, representing a useful biomarker for predicting the biological behavior and prognosis of gastric cancer. However, no significant association was observed between the expression of VEGF and T-cadherin.

Integrin-linked kinase mediates CTGF-induced epithelial to mesenchymal transition in alveolar type II epithelial cells

BACKGROUND

Overexpression of connective tissue growth factor (CTGF) in alveolar type II epithelial (AT II) cells disrupts alveolar structure, causes interstitial fibrosis, and upregulates integrin-linked kinase (ILK). Whether CTGF-ILK signaling induces epithelial to mesenchymal transition (EMT) in AT II cells is unknown.

METHODS

Transgenic mice with targeted overexpression of CTGF in AT II cells were generated utilizing the surfactant protein C (SP-C) gene promoter and doxycycline-inducible system. AT II cells were isolated from 4-wk-old CTGF-overexpressing (CTGF+) mice and control littermates, and cultured on Matrigel. Cells were transfected with ILK siRNA, and cell morphology and expression of cell differentiation markers were analyzed.

RESULTS

The AT II cells from the control lungs grew in clusters and formed alveolar-like cysts and expressed SP-C. In contrast, the cells from CTGF+ lungs were spread and failed to form alveolar-like cysts. These cells expressed higher levels of CTGF, α smooth muscle actin (α-SMA), fibronectin and vimentin, the mesenchymal markers, suggesting EMT-like changes. Transfection with ILK siRNA not only dramatically attenuated ILK expression, but also decreased α-SMA expression as well as reversed cell morphological changes in CTGF+ AT II cells.

CONCLUSION

Overexpression of CTGF induces EMT in mouse primary AT II cells and this is mediated by ILK.

Positive feedback regulation between adiponectin and T-cadherin impacts adiponectin levels in tissue and plasma of male mice

Adiponectin (Adipo), a multimeric adipocyte-secreted protein abundant in the circulation, is implicated in cardiovascular protective functions. Recent work documented that Adipo locally associates with responsive tissues through interactions with T-cadherin (Tcad), an atypical, glycosylphosphatidylinositol (GPI)-anchored cadherin cell surface glycoprotein. Mice deficient for Tcad lack tissue-associated Adipo, accumulate Adipo in the circulation, and mimic the Adipo knockout (KO) cardiovascular phenotype. In reverse, Tcad protein is visibly reduced from cardiac tissue in Adipo-KO mice, suggesting interdependent regulation of the 2 proteins. Here, we evaluate the effect of Adipo on Tcad protein expression. Adipo and Tcad proteins were colocalized in aorta, heart, and skeletal muscle. Adipo positively regulated levels of Tcad protein in vivo and in endothelial cell (EC) cultures. In Tcad-KO mice, binding of endogenous and exogenously administered Adipo to cardiovascular tissues was dramatically reduced. Consistently, knockdown of Tcad in cultured murine vascular ECs significantly diminished Adipo binding. In search for a possible mechanism, we found that enzymatic cleavage of Tcad with phosphatidylinositol-specific phospholipase C increases plasma Adipo while decreasing tissue-bound levels. Similarly, pretreatment of cultured ECs with serum containing Adipo attenuated phosphatidylinositol-specific phospholipase C-mediated Tcad cleavage. In vivo administration of adenovirus producing Adipo suppressed plasma levels of GPI phospholipase D, the endogenous cleavage enzyme for GPI-anchored proteins. In conclusion, our data show that both circulating and tissue-bound Adipo levels are dependent on Tcad and, in reverse, regulate tissue Tcad levels through a positive feedback loop that operates by suppressing phospholipase-mediated Tcad release from the cell surface.

Integrin-linked kinase inhibition attenuates permeability of the streptozotocin-induced diabetic rat retina

Integrin-linked kinase (ILK), as a multi-functional regulator, has been associated with diabetic retinopathy (DR). In this study, we investigated whether inhibition of ILK could result in therapeutic effects. Diabetes mellitus's rats were induced by streptozotocin (STZ) injection. After 1 weeks induction, rats were injected intraperitoneally daily with ILK inhibitor, QLT0267, at 5 mg/kg. Then, the rats were examined by 4, 8, and 12 weeks after first STZ injection. We found that QLT0267 treatment could not only lower ILK level in retina at as early as 3 weeks after the onset of diabetes but also attenuate retina permeability, which was measured by Evan's blue. Maximum effect was found in 11 weeks treatment. Meanwhile, QLT0267 did not disturbed blood glucose concentration. Furthermore, QLT0267 inhibited Akt (Ser473) activation and reduced expression of HIF1α and VEGF which were evaluated by western blot, real time PCR, and immunohistochemistry. We conclude that ILK may be a new target for DR.

Integrin-linked kinase plays a key role in the regulation of angiotensin II-induced renal inflammation

ILK (integrin-linked kinase) is an intracellular serine/threonine kinase involved in cell-matrix interactions. ILK dysregulation has been described in chronic renal disease and modulates podocyte function and fibrosis, whereas data about its role in inflammation are scarce. AngII (angiotensin II) is a pro-inflammatory cytokine that promotes renal inflammation. AngII blockers are renoprotective and down-regulate ILK in experimental kidney disease, but the involvement of ILK in the actions of AngII in the kidney has not been addressed. Therefore we have investigated whether ILK signalling modulates the kidney response to systemic AngII infusion in wild-type and ILK-conditional knockout mice. In wild-type mice, AngII induced an inflammatory response, characterized by infiltration of monocytes/macrophages and lymphocytes, and up-regulation of pro-inflammatory factors (chemokines, adhesion molecules and cytokines). AngII activated several intracellular signalling mechanisms, such as the NF-κB (nuclear factor κB) transcription factor, Akt and production of ROS (reactive oxygen species). All these responses were prevented in AngII-infused ILK-deficient mice. In vitro studies characterized further the mechanisms regulating the inflammatory response modulated by ILK. In cultured tubular epithelial cells ILK blockade, by siRNA, inhibited AngII-induced NF-κB subunit p65 phosphorylation and its nuclear translocation. Moreover, ILK gene silencing prevented NF-κB-related pro-inflammatory gene up-regulation. The results of the present study demonstrate that ILK plays a key role in the regulation of renal inflammation by modulating the canonical NF-κB pathway, and suggest a potential therapeutic target for inflammatory renal diseases.

C-ERC/mesothelin provokes lymphatic invasion of colorectal adenocarcinoma

BACKGROUND

Lymph node metastasis is a key event of colorectal cancer (CRC) progression. Mesothelin is expressed in various types of malignant tumor and associated with an unfavorable prognosis. The full-length mesothelin (Full-ERC) is cleaved by protease into membrane-bound C-ERC/mesothelin and N-ERC/mesothelin which is secreted into the blood. The aim of this study was to examine the biological role of mesothelin in CRC by clinicopathological analysis and in vitro lymphatic invasion assay.

METHODS

Ninety-one cases of CRC specimens were immunohistochemically examined and the localization of mesothelin in luminal membrane and/or cytoplasm was also evaluated. Lymphatic invasion assay was also performed using the human CRC cell line, WiDr, which was transfected with Full-, N- and C-ERC/mesothelin expression plasmids (Full-WiDr, N-WiDr and C-WiDr).

RESULTS

Immunohistochemically, "luminal membrane positive" of mesothelin was identified in 37.4 %, and correlated with lymphatic permeation and lymph node metastasis, but not with patients' prognosis. Interestingly, among the patients with lymph node metastasis (N = 38), "luminal membrane positive" of mesothelin significantly correlated with unfavorable patients' outcome. In addition, lymphatic invasion assay revealed that Full-WiDr and C-WiDr more significantly invaded human lymphatic endothelial cells than the Mock-WiDr (P < 0.01).

CONCLUSION

The luminal membrane expression of mesothelin was associated with unfavorable prognosis of CRC patients with lymph node metastasis. Moreover, this is the first report to prove the biological function of C-ERC/mesothelin associated with lymphatic invasion of cancer in vitro.

Novel mechanism regulating endothelial permeability via T-cadherin-dependent VE-cadherin phosphorylation and clathrin-mediated endocytosis

T-cadherin is a unique member of the cadherin superfamily of adhesion molecules. In contrast to “classical” cadherins, T-cadherin lacks transmembrane and cytoplasmic domains and is anchored to the cell membrane via a glycosilphosphoinositol moiety. T-cadherin is predominantly expressed in cardiovascular system. Clinical and biochemical studies evidence that expression of T-cadherin increases in post-angioplasty restenosis and atherosclerotic lesions—conditions associated with endothelial dysfunction and pathological expression of adhesion molecules. Here, we provide data suggesting a new signaling mechanism by which T-cadherin regulates endothelial permeability. T-cadherin overexpression leads to VE-cadherin phosphorylation on Y731 (β-catenin-binding site), VE-cadherin clathrin-dependent endocytosis and its degradation in lysosomes. Moreover, T-cadherin overexpression results in activation of Rho GTPases signaling and actin stress fiber formation. Thus, T-cadherin up-regulation is involved in degradation of a key endothelial adhesion molecule, VE-cadherin, resulting in the disruption of endothelial barrier function. Our results point to the role of T-cadherin in regulation of endothelial permeability and its possible engagement in endothelial dysfunction.

T-cadherin is essential for adiponectin-mediated revascularization

Adipose tissue secretes protein factors that have systemic actions on cardiovascular tissues. Previous studies have shown that ablation of the adipocyte-secreted protein adiponectin leads to endothelial dysfunction, whereas its overexpression promotes wound healing. However, the receptor(s) mediating the protective effects of adiponectin on the vasculature is not known. Here we examined the role of membrane protein T-cadherin, which localizes adiponectin to the vascular endothelium, in the revascularization response to chronic ischemia. T-cadherin-deficient mice were analyzed in a model of hind limb ischemia where blood flow is surgically disrupted in one limb and recovery is monitored over 28 days by laser Doppler perfusion imaging. In this model, T-cadherin-deficient mice phenocopy adiponectin-deficient mice such that both strains display an impaired blood flow recovery compared with wild-type controls. Delivery of exogenous adiponectin rescued the impaired revascularization phenotype in adiponectin-deficient mice but not in T-cadherin-deficient mice. In cultured endothelial cells, T-cadherin deficiency by siRNA knockdown prevented the ability of adiponectin to promote cellular migration and proliferation. These data highlight a previously unrecognized role for T-cadherin in limb revascularization and show that it is essential for mediating the vascular actions of adiponectin.

Impact of the ADHD-susceptibility gene CDH13 on development and function of brain networks

Attention-deficit/hyperactivity disorder (ADHD) is a common, early onset and enduring neuropsychiatric disorder characterized by developmentally inappropriate inattention, hyperactivity, increased impulsivity and motivational/emotional dysregulation with similar prevalence rates throughout different cultural settings. Persistence of ADHD into adulthood is associated with considerable risk for co-morbidities such as depression and substance use disorder. Although the substantial heritability of ADHD is well documented the etiology is characterized by a complex coherence of genetic and environmental factors rendering identification of risk genes difficult. Genome-wide linkage as well as single nucleotide polymorphism (SNP) and copy-number variant (CNV) association scans recently allow to reliably define aetiopathogenesis-related genes. A considerable number of novel ADHD risk genes implicate biological processes involved in neurite outgrowth and axon guidance. Here, we focus on the gene encoding Cadherin-13 (CDH13), a cell adhesion molecule which was replicably associated with liability to ADHD and related neuropsychiatric conditions. Based on its unique expression pattern in the brain, we discuss the molecular structure and neuronal mechanisms of Cadherin-13 in relation to other cadherins and the cardiovascular system. An appraisal of various Cadherin-13-modulated signaling pathways impacting proliferation, migration and connectivity of specific neurons is also provided. Finally, we develop an integrative hypothesis of the mechanisms in which Cadherin-13 plays a central role in the regulation of brain network development, plasticity and function. The review concludes with emerging concepts about alterations in Cadherin-13 signaling contributing to the pathophysiology of neurodevelopmental disorders.

Loss of T-cadherin (CDH-13) regulates AKT signaling and desensitizes cells to apoptosis in melanoma

An understanding of signaling pathways is a basic requirement for the treatment of melanoma. Currently, kinases are at the center of melanoma therapies. According to our research, additional alternative molecules are equally important for development of melanoma. In this regard, cancer progression is, among other factors, driven by an altered adhesion via cadherins. For instance, the de-regulated expression of the adhesion molecule T-cadherin is found in various cancer types, including melanoma, and influences migration and invasion. T-cadherin is thought to affect cellular function largely through its signaling and not its adhesion properties because the molecule is anchored into the cell membrane by a glycosylphosphatidylinositol (GPI) moiety. However, detailed knowledge about the consequences of the loss of T-cadherin in melanoma is currently lacking. For this reason, we were interested in assessing which signaling pathways are initiated by T-cadherin. The tumor growth of subcutaneously injected T-cadherin-positive melanoma cells was diminished compared with T-cadherin-negative cells in nude mice. The difference in tumor volume was not due to decreased proliferation but rather due to increased apoptosis. After the expression of T-cadherin was induced, we detected V-AKT murine thymoma viral oncogene homolog (AKT) and FoxO3a hypophosphorylation accompanied by the downregulation of the antiapoptotic molecules BCL-2, BCL-x and Clusterin. Furthermore, we detected a diminished transcriptional activity of CREB and AP-1. We demonstrated that T-cadherin functions as a pro-apoptotic tumor suppressor that antagonizes AKT/CREB/AP-1/FoxO3a signaling, whereas NFκB, TCF/LEF and mTOR are not part of the T-cadherin signaling pathway. Notably, we found that the restoration of T-cadherin in melanoma cells causes sensitization to apoptosis induced by CD95/Fas antibody CH-11.

Mild endoplasmic reticulum stress promotes retinal neovascularization via induction of BiP/GRP78

Endoplasmic reticulum (ER) stress occurs as a result of accumulation of unfolded or misfolded proteins in the ER and is involved in the mechanisms of various diseases, such as cancer and neurodegeneration. The goal of the present study was to clarify the relationship between ER stress and pathological neovascularization in the retina. Proliferation and migration of human retinal microvascular endothelial cells (HRMEC) were assessed in the presence of ER stress inducers, such as tunicamycin and thapsigargin. The expression of ER chaperone immunoglobulin heavy-chain binding protein (BiP), known as Grp78, was evaluated by real time RT-PCR, immunostaining, and Western blotting. Tunicamycin or thapsigargin was injected into the intravitreal body of oxygen-induced retinopathy (OIR) model mice at postnatal day 14 (P14) and retinal neovascularization was quantified at P17. The expression and localization of BiP in the retina was also evaluated in the OIR model. Exposure to tunicamycin and thapsigargin increased the proliferation and migration of HRMEC. Tunicamycin enhanced the expression of BiP in HRMEC at both the mRNA level and at the protein level on the cell surface, and increased the formation of a BiP/T-cadherin immunocomplex. In OIR model mice, retinal neovascularization was accelerated by treatments with ER stress inducers. BiP was particularly observed in the pathological vasculature and retinal microvascular endothelial cells, and the increase of BiP expression was correlated with retinal neovascularization. In conclusion, ER stress may contribute to the formation of abnormal vasculature in the retina via BiP complexation with T-cadherin, which then promotes endothelial cell proliferation and migration.

α-Catulin drives metastasis by activating ILK and driving an αvβ3 integrin signaling axis

α-Catulin is an oncoprotein that helps sustain proliferation by preventing cellular senescence. Here, we report that α-catulin also drives malignant invasion and metastasis. α-Catulin was upregulated in highly invasive non-small cell lung cancer (NSCLC) cell lines, where its ectopic expression or short-hairpin RNA-mediated attenuation enhanced or limited invasion or metastasis, respectively. α-Catulin interacted with integrin-linked kinase (ILK), a serine/threonine protein kinase implicated in cancer cell proliferation, antiapoptosis, invasion, and angiogenesis. Attenuation of ILK or α-catulin reciprocally blocked cell migration and invasion induced by the other protein. Mechanistic investigations revealed that α-catulin activated Akt-NF-κB signaling downstream of ILK, which in turn led to increased expression of fibronectin and integrin αvβ3. Pharmacologic or antibody-mediated blockade of NF-κB or αvβ3 was sufficient to inhibit α-catulin-induced cell migration and invasion. Clinically, high levels of expression of α-catulin and ILK were associated with poor overall survival in patients with NSCLC. Taken together, our study shows that α-catulin plays a critical role in cancer metastasis by activating the ILK-mediated Akt-NF-κB-αvβ3 signaling axis.

T-Cadherin is an auxiliary negative regulator of EGFR pathway activity in cutaneous squamous cell carcinoma: impact on cell motility

Genetic and epigenetic studies in different cancers, including cutaneous carcinomas, have implicated T-cadherin (T-cad) as a tumor suppressor. Immunohistochemical and in vitro studies have suggested that T-cad loss promotes incipient invasiveness in cutaneous squamous cell carcinoma (SCC). Molecular mechanisms are unknown. This study found that the main consequence of T-cad silencing in SCC is facilitation of ligand-dependent EGFR activation, whereas T-cad overexpression impedes EGFR activation. Gain- and loss-of-function studies in A431 SCC cells demonstrate T-cad-controlled responsiveness to EGF with respect to pharmacological inhibition of EGFR and to diverse signaling and functional events of the EGFR activation cascade (EGFR phosphorylation, internalization, nuclear translocation, cell retraction/de-adhesion, motility, invasion, integrin β1, and Rho small GTPases such as RhoA, Rac1, and Cdc42 activation). Further, T-cad modulates the EGFR pathway activity by influencing membrane compartmentalization of EGFR; T-cad upregulation promotes retention of EGFR in lipid rafts, whereas T-cad silencing releases EGFR from this compartment, rendering EGFR more accessible to ligand stimulation. This study reveals a mechanism for fine-tuning of EGFR activity in SCC, whereby T-cad represents an auxiliary "negative" regulator of the EGFR pathway, which impacts invasion-associated behavioral responses of SCC to EGF. This action of T-cad in SCC may serve as a paradigm explaining other malignancies displaying concomitant T-cad loss and enhanced EGFR activity.

Mesothelin overexpression promotes mesothelioma cell invasion and MMP-9 secretion in an orthotopic mouse model and in epithelioid pleural mesothelioma patients

PURPOSE

Mesothelin (MSLN) is a tumor-associated antigen, being investigated as a biomarker and therapeutic target in malignant pleural mesothelioma (MPM). The biologic function of MSLN overexpression in MPM is unknown. We hypothesized that MSLN may promote tumor invasion in MPM, a tumor characterized primarily by regional aggressiveness and rare distant metastases.

EXPERIMENTAL DESIGN

Human and murine MPM cells with MSLN forced expression and short hairpin RNA knockdown were examined for proliferation, invasion, and matrix metalloproteinase (MMP) secretion. The influence of MSLN overexpression on MPM cell invasion was assessed in an orthotopic mouse model and in patient samples.

RESULTS

MSLN expression promotes MPM cell invasion and MMP secretion in both human and murine MPM cells. In an orthotopic MPM mouse model characterized by our laboratory, MPM cells with MSLN overexpression preferentially localized to the tumor invading edge, colocalized with MMP-9 expression, and promoted decreased survival without an increase in tumor burden progression. In a tissue microarray from epithelioid MPM patients (n = 139, 729 cores), MSLN overexpression correlated with higher MMP-9 expression at individual core level. Among stage III MPM patients (n = 72), high MSLN expression was observed in 26% of T2 tumors and 51% of T3 tumors.

CONCLUSIONS

Our data provide evidence elucidating a biologic role for MSLN as a factor promoting tumor invasion and MMP-9 expression in MSLN expressing MPM. As regional invasion is the characteristic feature in MSLN expressing solid cancers (MPM, pancreas, and ovarian), our observations add rationale to studies investigating MSLN as a therapeutic target.

T-cadherin attenuates insulin-dependent signalling, eNOS activation, and angiogenesis in vascular endothelial cells

AIMS

T-cadherin (T-cad) is a glycosylphosphatidylinositol-anchored cadherin family member. Experimental, clinical, and genomic studies suggest a role for T-cad in vascular disorders such as atherosclerosis and hypertension, which are associated with endothelial dysfunction and insulin resistance (InsRes). In endothelial cells (EC), T-cad and insulin activate similar signalling pathways [e.g. PI3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR)] and processes (e.g. angiogenesis). We hypothesize that T-cad is a regulatory component of insulin signalling in EC and therefore a determinant of the development of endothelial InsRes.

METHODS AND RESULTS

We investigated T-cad-dependent effects on insulin sensitivity using human EC stably transduced with respect to T-cad overexpression or T-cad silencing. Responsiveness to insulin was examined at the level of effectors of the insulin signalling cascade, EC nitric oxide synthase (eNOS) activation, and angiogenic behaviour. Overexpression and ligation of T-cad on EC attenuates insulin-dependent activation of the PI3K/Akt/mTOR signalling axis, eNOS, EC migration, and angiogenesis. Conversely, T-cad silencing enhances these actions of insulin. Attenuation of EC responsiveness to insulin results from T-cad-mediated chronic activation of the Akt/mTOR-dependent negative feedback loop of the insulin cascade and enhanced degradation of the insulin receptor (IR) substrate. Co-immunoprecipitation experiments revealed an association between T-cad and IR. Filipin abrogated inhibitory effects of T-cad on insulin signalling, demonstrating localization of T-cad-insulin cross-talk to lipid raft plasma membrane domains. Hyperinsulinaemia up-regulates T-cad mRNA and protein levels in EC.

CONCLUSION

T-cad expression modulates signalling and functional responses of EC to insulin. We have identified a novel signalling mechanism regulating insulin function in the endothelium and attribute a role for T-cad up-regulation in the pathogenesis of endothelial InsRes.

T-cadherin (Cdh13) in association with pancreatic β-cell granules contributes to second phase insulin secretion

Glucose homeostasis depends on adequate control of insulin secretion. We report the association of the cell-adhesion and adiponectin (APN)-binding glycoprotein T-cadherin (Cdh13) with insulin granules in mouse and human β-cells. Immunohistochemistry and electron microscopy of islets in situ and targeting of RFP-tagged T-cadherin to GFP-labeled insulin granules in isolated β-cells demonstrate this unusual location. Analyses of T-cadherin-deficient (Tcad-KO) mice show normal islet architecture and insulin content. However, T-cadherin is required for sufficient insulin release in vitro and in vivo. Primary islets from Tcad-KO mice were defective in glucose-induced but not KCl-mediated insulin secretion. In vivo, second phase insulin release in T-cad-KO mice during a hyperglycemic clamp was impaired while acute first phase release was unaffected. Tcad-KO mice showed progressive glucose intolerance by 5 mo of age without concomitant changes in peripheral insulin sensitivity. Our analyses detected no association of APN with T-cadherin on β-cell granules although colocalization was observed on the pancreatic vasculature. These data identify T-cadherin as a novel component of insulin granules and suggest that T-cadherin contributes to the regulation of insulin secretion independently of direct interactions with APN.

GSK-3β/CREB axis mediates IGF-1-induced ECM/adhesion molecule expression, cell cycle progression and monolayer permeability in retinal capillary endothelial cells: Implications for diabetic retinopathy

Various growth factors and cytokines are implicated in endothelial dysfunction and blood-retinal barrier (BRB) breakdown in early diabetic retinopathy (DR). However, cellular and molecular mechanisms that may underlie the pathology of DR are not fully understood yet. We therefore examined the effect of insulin-like growth factor (IGF)-1 on ECM/adhesion molecule expression, cell cycle regulation and monolayer permeability in an endothelial cell line (TR-iBRB2). We investigate whether the action of IGF-1 (1) involves glycogen synthase kinase 3beta (GSK-3β) and cAMP responsive transcription factor (CREB) and (2) alters ECM/adhesion molecule gene expression. Treatment of TR-iBRB2 cell with IGF-1 (100ng/ml for 0-24h) increases phosphorylation of (i) Akt Thr308, and its substrates including GSK-3β at Ser9, which inactivates its kinase function, and (ii) CREB at Ser133 (activation). These phosphorylations correlate positively with enhanced expression of CREB targets such as ECM protein fibronectin and cell cycle progression factor cyclin D1. However, stable transfection of a mutant GSK3β(S9A) or a dominant negative K-CREB in TR-iBRB2 prevents IGF-1-induced fibronectin and cyclin D1 expression. Furthermore, IGF-1 reduces the level of intercellular adherence molecule VE-cadherin and increases monolayer permeability in TR-iBRB2 cells when measured by FITC-dextran leakage. The effect of IGF-1 on VE-cadherin and membrane permeability is absent in TR-iBRB2 cells expressing the GSK-3β(S9A). Similarly, K-CREB reverses IGF-1 down-regulation of VE-cadherin and up-regulation of fibronectin. These results indicate that GSK-3β/CREB axis alters ECM/adhesion molecule expression and cell cycle progression in retinal endothelial cells, and may potentially contribute to endothelial dysfunction and BRB leakage in DR.

Excessive hepatomegaly of mice with hepatocyte-targeted elimination of integrin linked kinase following treatment with 1,4-bis [2-(3,5-dichaloropyridyloxy)] benzene

TCBOPOP (1,4-bis [2-(3,5-dichaloropyridyloxy)] benzene) an agonist of the constitutive androstane receptor (CAR), produces rapid hepatocyte hyperplasia and hepatomegaly in the absence of hepatic injury. In this study we demonstrate that integrin-linked kinase (ILK), which is involved in transmission of the extracellular matrix (ECM) signaling by way of integrin receptors, plays an important role in regulating TCPOBOP-induced proliferation of hepatocytes and hepatomegaly. Hepatocyte-specific ILK knockout mice (ILK/liver-/- mice) and wildtype mice (WT) were given a single dose of TCPOBOP (3 mg/kg) by oral gavage. Mice were sacrificed at days 1, 2, 5, and 7 after TCPOBOP administration. WT mice showed maximum proliferation on days 1 and 2, which came back to baseline levels by days 5 and 7 after TCPOBOP administration. The ILK/liver-/- mice, on the other hand, showed a prolonged and a sustained proliferative response as evident by an increased number of proliferative cell nuclear antigen assay (PCNA)-positive cells even at days 5 and 7 after TCPOBOP administration. At day 7 the WT mice showed close to a 2.5-fold increase in liver weight, whereas the ILK/liver-/- mice showed a 3.7-fold increase in liver weight. The prolonged proliferative response in the ILK/liver-/- mice seems to be due to sustained induction of CAR leading to sustained induction of c-Myc, which is known to be a key mediator of TCPOPOP-CAR induced direct liver hyperplasia.

CONCLUSION

The data indicate that ECM-mediated signaling by way of ILK is essential for adjustment of final liver size and proper termination of TCPOBOP-induced proliferation of hepatocytes.

T-cadherin is critical for adiponectin-mediated cardioprotection in mice

The circulating, adipocyte-secreted hormone adiponectin (APN) exerts protective effects on the heart under stress conditions. The receptors binding APN to cardiac tissue, however, have remained elusive. Here, we report that the glycosyl phosphatidylinositol–anchored cell surface glycoprotein T-cadherin (encoded by Cdh13) protects against cardiac stress through its association with APN in mice. We observed extensive colocalization of T-cadherin and APN on cardiomyocytes in vivo. In T-cadherin-deficient mice, APN failed to associate with cardiac tissue, and its levels dramatically increased in the circulation. Pressure overload stress resulted in exacerbated cardiac hypertrophy in T-cadherin-null mice and paralleled corresponding defects in mice lacking APN. During ischemia-reperfusion injury, the absence of T-cadherin increased infarct size similar to that in APN-null mice. Myocardial AMPK is a major downstream protective signaling target of APN. In both cardiac hypertrophy and ischemia-reperfusion models, T-cadherin was necessary for APN-dependent AMPK phosphorylation. In APN-null mice, recombinant adenovirus-expressed APN reduced exaggerated hypertrophy and infarct size and restored AMPK phosphorylation as previously reported. In contrast, rescue was ineffective in mice lacking T-cadherin in addition to APN. These data suggest that T-cadherin protects from stress-induced pathological cardiac remodeling by binding APN and activating its cardioprotective functions.

ILK mediates the effects of strain on intestinal epithelial wound closure

The intestinal epithelium is subjected to repetitive deformation during normal gut function by peristalsis and villous motility. Such repetitive strain promotes intestinal epithelial migration across fibronectin in vitro, but signaling mediators for this are poorly understood. We hypothesized that integrin-linked kinase (ILK) mediates strain-stimulated migration in intestinal epithelial cells cultured on fibronectin. ILK kinase activity increased rapidly 5 min after strain induction in both Caco-2 and intestinal epithelial cell-6 (IEC-6) cells. Wound closure in response to strain was reduced in ILK small interfering RNA (siRNA)-transfected Caco-2 cell monolayers when compared with control siRNA-transfected Caco-2 cells. Pharmacological blockade of phosphatidylinositol-3 kinase (PI3K) or Src or reducing Src by siRNA prevented strain activation of ILK. ILK coimmunoprecipitated with focal adhesion kinase (FAK), and this association was decreased by mutation of FAK Tyr925 but not FAK Tyr397. Strain induction of FAK Tyr925 phosphorylation but not FAK Tyr397 or FAK Tyr576 phosphorylation was blocked in ILK siRNA-transfected cells. ILK-Src association was stimulated by strain and was blocked by the Src inhibitor PP2. Finally, ILK reduction by siRNA inhibited strain-induced phosphorylation of myosin light chain and Akt. These results suggest a strain-dependent signaling pathway in which ILK association with FAK and Src mediates the subsequent downstream strain-induced motogenic response and suggest that ILK induction by repetitive deformation may contribute to recovery from mucosal injury and restoration of the mucosal barrier in patients with prolonged ileus. ILK may therefore be an important target for intervention to maintain the mucosa in such patients.

Cadherin 13 in cancer

We review the evidence suggesting the involvement of Cadherin 13 (CDH13, T-cadherin, H-cadherin) in various cancers. CDH13 is an atypical member of the cadherin family, devoid of a transmembrane domain and anchored to the exterior surface of the plasma membrane via a glycosylphosphatidylinositol anchor. CDH13 is thought to affect cellular behavior largely through its signaling properties. It is often down-regulated in cancerous cells. CDH13 down-regulation has been associated with poorer prognosis in various carcinomas, such as lung, ovarian, cervical and prostate cancer. CDH13 re-expression in most cancer cell lines inhibits cell proliferation and invasiveness, increases susceptibility to apoptosis, and reduces tumor growth in in vivo models. These properties suggest that CDH13 may represent a possible target for therapy in some cancers. At the same time, CDH13 is up-regulated in blood vessels growing through tumors and promotes tumor neovascularization. In contrast to most cancer cell lines, CDH13 overexpression in endothelial cells promotes their proliferation and migration, and has a pro-survival effect. We also discuss molecular mechanisms that may regulate CDH13 expression and underlie its roles in cancer.

Integrin-linked kinase is a functional Mn2+-dependent protein kinase that regulates glycogen synthase kinase-3β (GSK-3beta) phosphorylation

Background

Integrin-linked kinase (ILK) is a highly evolutionarily conserved, multi-domain signaling protein that localizes to focal adhesions, myofilaments and centrosomes where it forms distinct multi-protein complexes to regulate cell adhesion, cell contraction, actin cytoskeletal organization and mitotic spindle assembly. Numerous studies have demonstrated that ILK can regulate the phosphorylation of various protein and peptide substrates in vitro, as well as the phosphorylation of potential substrates and various signaling pathways in cultured cell systems. Nevertheless, the ability of ILK to function as a protein kinase has been questioned because of its atypical kinase domain.

Methodology/Principal Findings

Here, we have expressed full-length recombinant ILK, purified it to >94% homogeneity, and characterized its kinase activity. Recombinant ILK readily phosphorylates glycogen synthase kinase-3 (GSK-3) peptide and the 20-kDa regulatory light chains of myosin (LC₂₀). Phosphorylation kinetics are similar to those of other active kinases, and mutation of the ATP-binding lysine (K220 within subdomain 2) causes marked reduction in enzymatic activity. We show that ILK is a Mn-dependent kinase (the K_m for MnATP is ∼150-fold less than that for MgATP).

Conclusions/Significance

Taken together, our data demonstrate that ILK is a bona fide protein kinase with enzyme kinetic properties similar to other active protein kinases.

T-cadherin modulates endothelial barrier function

T-cadherin is an atypical member of the cadherin family, which lacks the transmembrane and intracellular domains and is attached to the plasma membrane via a glycosylphosphatidylinositol anchor. Unlike canonical cadherins, it is believed to function primarily as a signaling molecule. T-cadherin is highly expressed in endothelium. Using transendothelial electrical resistance measurements and siRNA-mediated depletion of T-cadherin in human umbilical vein endothelial cells, we examined its involvement in regulation of endothelial barrier. We found that in resting confluent monolayers adjusted either to 1% or 10% serum, T-cadherin depletion modestly, but consistently reduced transendothelial resistance. This was accompanied by increased phosphorylation of Akt and LIM kinase, reduced phosphorylation of p38 MAP kinase, but no difference in tubulin acetylation and in phosphorylation of an actin filament severing protein cofilin and myosin light chain kinase. Serum stimulation elicited a biphasic increase in resistance with peaks at 0.5 and 4-5 h, which was suppressed by a PI3 kinase/Akt inhibitor wortmannin and a p38 inhibitor SB 239063. T-cadherin depletion increased transendothelial resistance between the two peaks and reduced the amplitude of the second peak. T-cadherin depletion abrogated serum-induced Akt phosphorylation at Thr308 and reduced phosphorylation at Ser473, reduced phosphorylation of cofilin, and accelerated tubulin deacetylation. Adiponectin slightly improved transendothelial resistance irrespectively of T-cadherin depletion. T-cadherin depletion also resulted in a reduced sensitivity and delayed responses to thrombin. These data implicate T-cadherin in regulation of endothelial barrier function, and suggest a complex signaling network that links T-cadherin and regulation of barrier function.

T-cadherin is located in the nucleus and centrosomes in endothelial cells

T-cadherin (H-cadherin, cadherin 13) is upregulated in vascular proliferative disorders and in tumor-associated neovascularization and is deregulated in many cancers. Unlike canonical cadherins, it lacks transmembrane and intracellular domains and is attached to the plasma membrane via a glycosylphosphatidylinositol anchor. T-cadherin is thought to function in signaling rather than as an adhesion molecule. Some interactive partners of T-cadherin at the plasma membrane have recently been identified. We examined T-cadherin location in human endothelial cells using confocal microscopy and subcellular fractionation. We found that a considerable proportion of T-cadherin is located in the nucleus and in the centrosomes. T-cadherin colocalized with a centrosomal marker gamma-tubulin uniformly throughout the cell cycle at least in human umbilical vein endothelial cells. In the telophase, T-cadherin transiently concentrated in the midbody and was apparently degraded. Its overexpression resulted in an increase in the number of multinuclear cells, whereas its downregulation by small interfering RNA led to an increase in the number of cells with multiple centrosomes. These findings indicate that deregulation of T-cadherin in endothelial cells may lead to disturbances in cytokinesis or centrosomal replication.

Extracellular cadherin repeat domains EC1 and EC5 of T-cadherin are essential for its ability to stimulate angiogenic behavior of endothelial cells

T-cadherin (T-cad) promotes survival, proliferation, and migration of endothelial cells and induces angiogenesis. We aimed to identify domains of T-cad functionally relevant to its effects on endothelial cell behavior. To specifically target the functional properties of the 5 cadherin repeat domains (EC1-EC5) of T-cad, endothelial cells were transduced with lentivectors containing specific T-cad-domain-deletion mutant constructs (DeltaI, DeltaII, DeltaIII, DeltaIV, DeltaV). Empty (E) lentivector-transduced cells served as control. Similarly to overexpression of native T-cad, cells expressing DeltaII, DeltaIII, or DeltaIV displayed elevated levels of p-Akt and p-GSK3beta and increased proliferation rates (for DeltaII, DeltaIII) vs. E. DeltaI- and DeltaV-transduced cells exhibited reduced levels of p-Akt and p-GSK3beta and retarded growth rates vs. E. Stimulatory effects of native T-cad overexpression on Akt and GSK3beta phosphorylation were dose dependently inhibited by coexpression of DeltaI or DeltaV. Subsequent functional analyses compared only DeltaI-, DeltaII-, and DeltaV-mutant constructs with E as a negative control. Unlike DeltaII cells, DeltaI and DeltaV cells failed to exhibit homophilic ligation and deadhesion responses on a substratum of T-cad protein. In the wound assay, migration was increased for DeltaII cells but impaired for DeltaI and DeltaV cells. In endothelial cell-spheroid assay, angiogenic sprouting was augmented for DeltaII cells but inhibited for DeltaI and DeltaV cells. We conclude that EC1 and EC5 domains of T-cad are essential for its proangiogenic effects. DeltaI and DeltaV constructs may serve as dominant-negative mutants and as potential tools targeting excessive angiogenesis.

Inhibition of integrin-linked kinase attenuates renal interstitial fibrosis

Integrin-linked kinase (ILK) is an intracellular serine/threonine protein kinase that regulates cell adhesion, survival, and epithelial-to-mesenchymal transition (EMT). In this study, we investigated the kinase activity of ILK during tubular EMT induced by TGF-beta1 and examined the therapeutic potential of an ILK inhibitor in obstructive nephropathy. TGF-beta1 induced a biphasic activation of ILK in renal tubular epithelial cells, with rapid activation starting at 5 min and the second wave of activation peaking at 24 h; the latter paralleled the induction of ILK protein expression. Pharmacologic inhibition of ILK with small-molecule inhibitor QLT-0267 abolished TGF-beta1-induced phosphorylation of Akt and glycogen synthase kinase-3beta, suppressed cyclin D1 expression, and largely restored the expression of E-cadherin and zonula occludens 1. Inhibition of ILK also blocked TGF-beta1-mediated induction of fibronectin, Snail1, plasminogen activator inhibitor 1, and matrix metalloproteinase 2. In a mouse model of obstructive nephropathy, administration of QLT-0267 inhibited beta-catenin accumulation; suppressed Snail1, alpha-smooth muscle actin, fibronectin, vimentin, and type I and type III collagen expression; and reduced total tissue collagen content. Inhibition of ILK did not affect kidney structure or function in normal mice. These findings suggest that increased ILK activity mediates EMT and the progression of renal fibrosis. Pharmacologic inhibition of ILK signaling may hold therapeutic potential for fibrotic kidney diseases.

Spatial coordination of actin polymerization and ILK-Akt2 activity during endothelial cell migration

Eukaryotic cell migration proceeds by cycles of protrusion, adhesion, and contraction, regulated by actin polymerization, focal adhesion assembly, and matrix degradation. However, mechanisms coordinating these processes remain largely unknown. Here, we show that local regulation of thymosin-beta4 (Tbeta4) binding to actin monomer (G-actin) coordinates actin polymerization with metalloproteinase synthesis to promote endothelial cell motility. In particular and quite unexpectedly, FRET analysis reveals diminished interaction between Tbeta4 and G-actin at the cell leading edge despite their colocalization there. Profilin-dependent dissociation of G-actin-Tbeta4 complexes simultaneously liberates actin for filament assembly and facilitates Tbeta4 binding to integrin-linked kinase (ILK) in the lamellipodia. Tbeta4-ILK complexes then recruit and activate Akt2, resulting in matrix metalloproteinase-2 production. Thus, the actin-Tbeta4 complex constitutes a latent coordinating center for cell migratory behavior, allowing profilin to initiate a cascade of events at the leading edge that couples actin polymerization to matrix degradation.

A requirement for thioredoxin in redox-sensitive modulation of T-cadherin expression in endothelial cells

T-cad (T-cadherin), a glycosylphosphatidylinositol-anchored cadherin superfamily member, is expressed widely in the brain and cardiovascular system, and absent, decreased, or even increased, in cancers. Mechanisms controlling T-cad expression are poorly understood. The present study investigated transcriptional regulation of T-cad in ECs (endothelial cells). Conditions of oxidative stress (serum-deprivation or presence of H(2)O(2)) elevate T-cad mRNA and protein levels in ECs. Reporter gene analysis, using serially deleted T-cad promoter stretches ranging from -99 to -2304 bp, located the minimal promoter region of T-cad within -285 bp from the translation start site. Reporter activity in ECs transfected with the -285 bp construct increased under conditions of oxidative stress, and this was normalized by antioxidant N-acetylcysteine. An electrophoretic-mobility-shift assay revealed a specific nucleoprotein complex unique to -156 to -203 bp, which increased when nuclear extracts from oxidatively stressed ECs were used, suggesting the presence of redox-sensitive binding element(s). MS analysis of the nucleoprotein complex unique to -156 to -203 bp after streptavidin-agarose pull-down detected the presence of the redox-active protein thioredoxin. The presence of thioredoxin-1 in a nuclear extract from oxidatively stressed ECs was demonstrated after immunoprecipitation and immunoblotting. Transfection of ECs with thioredoxin-1 small interfering RNA abrogated oxidative-stress-induced up-regulation of T-cad transcripts and protein. We conclude that thioredoxin-1 is an important determinant of redox-sensitive transcriptional up-regulation of T-cad in ECs.

Integrin-linked kinase--essential roles in physiology and cancer biology

Integrin-linked kinase (ILK) is a multifunctional intracellular effector of cell-matrix interactions and regulates many cellular processes, including growth, proliferation, survival, differentiation, migration, invasion and angiogenesis. The use of recently developed Cre-lox-driven recombination and RNA-interference technologies has enabled the evaluation of the physiological roles of ILK in several major organ systems. Significant developmental and tissue-homeostasis defects occur when the gene that encodes ILK is deleted, whereas the expression of ILK is often elevated in human malignancies. Although the cause(s) of ILK overexpression remain to be fully elucidated, accumulating evidence suggests that its oncogenic capacity derives from its regulation of several downstream targets that provide cells with signals that promote proliferation, survival and migration, supporting the concept that ILK is a relevant therapeutic target in human cancer. Furthermore, a global analysis of the ILK 'interactome' has yielded several novel interactions, and has revealed exciting and unexpected cellular functions of ILK that might have important implications for the development of effective therapeutic agents.

Molecular genetics of adult ADHD: converging evidence from genome-wide association and extended pedigree linkage studies

A genome-wide association (GWA) study with pooled DNA in adult attention-deficit/hyperactivity disorder (ADHD) employing approximately 500K SNP markers identifies novel risk genes and reveals remarkable overlap with findings from recent GWA scans in substance use disorders. Comparison with results from our previously reported high-resolution linkage scan in extended pedigrees confirms several chromosomal loci, including 16q23.1-24.3 which also reached genome-wide significance in a recent meta-analysis of seven linkage studies (Zhou et al. in Am J Med Genet Part B, 2008). The findings provide additional support for a common effect of genes coding for cell adhesion molecules (e.g., CDH13, ASTN2) and regulators of synaptic plasticity (e.g., CTNNA2, KALRN) despite the complex multifactorial etiologies of adult ADHD and addiction vulnerability.

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.

Identification of proteins associating with glycosylphosphatidylinositol- anchored T-cadherin on the surface of vascular endothelial cells: role for Grp78/BiP in T-cadherin-dependent cell survival

There is scant knowledge regarding how cell surface lipid-anchored T-cadherin (T-cad) transmits signals through the plasma membrane to its intracellular targets. This study aimed to identify membrane proteins colocalizing with atypical glycosylphosphatidylinositol (GPI)-anchored T-cad on the surface of endothelial cells and to evaluate their role as signaling adaptors for T-cad. Application of coimmunoprecipitation from endothelial cells expressing c-myc-tagged T-cad and high-performance liquid chromatography revealed putative association of T-cad with the following proteins: glucose-related protein GRP78, GABA-A receptor alpha1 subunit, integrin beta3, and two hypothetical proteins, LOC124245 and FLJ32070. Association of Grp78 and integrin beta3 with T-cad on the cell surface was confirmed by surface biotinylation and reciprocal immunoprecipitation and by confocal microscopy. Use of anti-Grp78 blocking antibodies, Grp78 small interfering RNA, and coexpression of constitutively active Akt demonstrated an essential role for surface Grp78 in T-cad-dependent survival signal transduction via Akt in endothelial cells. The findings herein are relevant in the context of both the identification of transmembrane signaling partners for GPI-anchored T-cad as well as the demonstration of a novel mechanism whereby Grp78 can influence endothelial cell survival as a cell surface signaling receptor rather than an intracellular chaperone.