Nck-2, a novel Src homology2/3-containing adaptor protein that interacts with the LIM-only protein PINCH and components of growth factor receptor kinase-signaling pathways

Adapting to change: resolving the dynamic and dual roles of NCK1 and NCK2

Adaptor proteins play central roles in the assembly of molecular complexes and co-ordinated activation of specific pathways. Through their modular domain structure, the NCK family of adaptor proteins (NCK1 and NCK2) link protein targets via their single SRC Homology (SH) 2 and three SH3 domains. Classically, their SH2 domain binds to phosphotyrosine motif-containing receptors (e.g. receptor tyrosine kinases), while their SH3 domains bind polyproline motif-containing cytoplasmic effectors. Due to these functions being established for both NCK1 and NCK2, their roles were inaccurately assumed to be redundant. However, in contrast with this previously held view, NCK1 and NCK2 now have a growing list of paralog-specific functions, which underscores the need to further explore their differences. Here we review current evidence detailing how these two paralogs are unique, including differences in their gene/protein regulation, binding partners and overall contributions to cellular functions. To help explain these contrasting characteristics, we then discuss SH2/SH3 structural features, disordered interdomain linker regions and post-translational modifications. Together, this review seeks to highlight the importance of distinguishing NCK1 and NCK2 in research and to pave the way for investigations into the origins of their interaction specificity.

Isoform Switching Regulates the Response to Ionizing Radiation Through SRSF1

PURPOSE

This study investigated how isoform switching affects the cellular response to ionizing radiation (IR), an understudied area despite its relevance to radiation therapy in cancer treatment. We aimed to identify changes in transcript isoform expression post-IR exposure and the proteins mediating these changes, with a focus on their potential to modulate radiosensitivity.

METHODS AND MATERIALS

Using RNA sequencing, we analyzed the B-cell lines derived from 10 healthy individuals at 3 timepoints, applying the mixture of isoforms algorithm to quantify alternative splicing. We examined RNA binding protein motifs within the sequences of IR-responsive isoforms and validated the serine/arginine-rich splicing factor 1 (SRSF1) as a predominant mediator through RNA immunoprecipitation. We further investigated the effects of SRSF1 on radiosensitivity by RNA interference and by analyzing publicly available data on patients with cancer.

RESULTS

We identified ∼1900 radiation-responsive alternatively spliced isoforms. Many isoforms were differentially expressed without changes in their overall gene expression. Over a third of these transcripts underwent exon skipping, while others used proximal last exons. These IR-responsive isoforms tended to be shorter transcripts missing vital domains for preventing apoptosis and promoting cell division but retaining those necessary for DNA repair. Our combined computational, genetic, and molecular analyses identified the proto-oncogene SRSF1 as a mediator of these radiation-induced isoform-switching events that promote apoptosis. After exposure to DNA double-strand break-inducing agents, SRSF1 expression decreased. A reduction in SRSF1 increased radiosensitivity in vitro and among patients with cancer.

CONCLUSIONS

We establish a pivotal role for isoform switching in the cellular response to IR and propose SRSF1 as a promising biomarker for assessing radiation therapy effectiveness.

Distinct Requirements for Adaptor Proteins NCK1 and NCK2 in Mammary Gland Development

The adaptor proteins NCK1 and NCK2 are well-established signalling nodes that regulate diverse biological processes including cell proliferation and actin dynamics in many tissue types. Here we have investigated the distribution and function of Nck1 and Nck2 in the developing mouse mammary gland. Using publicly available single-cell RNA sequencing data, we uncovered distinct expression profiles between the two paralogs. Nck1 showed widespread expression in luminal, basal, stromal and endothelial cells, while Nck2 was restricted to luminal and basal cells, with prominent enrichment in hormone-sensing luminal subtypes. Next, using mice with global knockout of Nck1 or Nck2, we assessed mammary gland development during and after puberty (5, 8 and 12 weeks of age). Mice lacking Nck1 or Nck2 displayed significant defects in ductal outgrowth and branching at 5 weeks compared to controls, and the defects persisted in Nck2 knockout mice at 8 weeks before normalizing at 12 weeks. These defects were accompanied by an increase in epithelial cell proliferation at 5 weeks and a decrease at 8 weeks in both Nck1 and Nck2 knockout mice. We also profiled expression of several key genes associated with mammary gland development at these timepoints and detected temporal changes in transcript levels of hormone receptors as well as effectors of cell proliferation and migration in Nck1 and Nck2 knockout mice, in line with the distinct phenotypes observed at 5 and 8 weeks. Together these studies reveal a requirement for NCK proteins in mammary gland morphogenesis, and suggest that deregulation of Nck expression could drive breast cancer progression and metastasis.

Genome-wide association study for systemic lupus erythematosus in an egyptian population

Systemic lupus erythematosus (SLE) susceptibility has a strong genetic component. Genome-wide association studies (GWAS) across trans-ancestral populations show both common and distinct genetic variants of susceptibility across European and Asian ancestries, while many other ethnic populations remain underexplored. We conducted the first SLE GWAS on Egyptians-an admixed North African/Middle Eastern population-using 537 patients and 883 controls. To identify novel susceptibility loci and replicate previously known loci, we performed imputation-based association analysis with 6,382,276 SNPs while accounting for individual admixture. We validated the association analysis using adaptive permutation tests (n = 109). We identified a novel genome-wide significant locus near IRS1/miR-5702 (Pcorrected = 1.98 × 10-8) and eight novel suggestive loci (Pcorrected < 1.0 × 10-5). We also replicated (Pperm < 0.01) 97 previously known loci with at least one associated nearby SNP, with ITGAM, DEF6-PPARD and IRF5 the top three replicated loci. SNPs correlated (r 2 > 0.8) with lead SNPs from four suggestive loci (ARMC9, DIAPH3, IFLDT1, and ENTPD3) were associated with differential gene expression (3.5 × 10-95 < p < 1.0 × 10-2) across diverse tissues. These loci are involved in cellular proliferation and invasion-pathways prominent in lupus and nephritis. Our study highlights the utility of GWAS in an admixed Egyptian population for delineating new genetic associations and for understanding SLE pathogenesis.

PINCH1 Promotes Fibroblast Migration in Extracellular Matrices and Influences Their Mechanophenotype

Cell migration performs a critical function in numerous physiological processes, including tissue homeostasis or wound healing after tissue injury, as well as pathological processes that include malignant progression of cancer. The efficiency of cell migration and invasion appears to be based on the mechano-phenotype of the cytoskeleton. The properties of the cytoskeleton depend on internal cytoskeletal and external environmental factors. A reason for this are connections between the cell and its local matrix microenvironment, which are established by cell-matrix adhesion receptors. Upon activation, focal adhesion proteins such as PINCH1 are recruited to sites where focal adhesions form. PINCH1 specifically couples through interactions with ILK, which binds to cell matrix receptors and the actomyosin cytoskeleton. However, the role of PINCH1 in cell mechanics regulating cellular motility in 3D collagen matrices is still unclear. PINCH1 is thought to facilitate 3D motility by regulating cellular mechanical properties, such as stiffness. In this study, PINCH1 wild-type and knock-out cells were examined for their ability to migrate in dense extracellular 3D matrices. Indeed, PINCH1 wild-type cells migrated more numerously and deeper in 3D matrices, compared to knock-out cells. Moreover, cellular deformability was determined, e.g., elastic modulus (stiffness). PINCH1 knock-out cells are more deformable (compliable) than PINCH1 wild-type cells. Migration of both PINCH1−/− cells and PINCH1fl/fl cells was decreased by Latrunculin A inhibition of actin polymerization, suggesting that actin cytoskeletal differences are not responsible for the discrepancy in invasiveness of the two cell types. However, the mechanical phenotype of PINCH1−/− cells may be reflected by Latrunculin A treatment of PINCH1fl/fl cells, as they exhibit resembling deformability to untreated PINCH1−/− cells. Moreover, an apparent mismatch exists between the elongation of the long axis and the contraction of the short axis between PINCH1fl/fl cells and PINCH1−/− cells following Latrunculin A treatment. There is evidence of this indicating a shift in the proxy values for Poisson’s ratio in PINCH1−/− cells compared with PINCH1fl/fl cells. This is probably attributable to modifications in cytoskeletal architecture. The non-muscle myosin II inhibitor Blebbistatin also reduced the cell invasiveness in 3D extracellular matrices but instead caused a stiffening of the cells. Finally, PINCH1 is apparently essential for providing cellular mechanical stiffness through the actin cytoskeleton, which regulates 3D motility.

How signaling pathways link extracellular mechano-environment to proline biosynthesis: A hypothesis: PINCH-1 and kindlin-2 sense mechanical signals from extracellular matrix and link them to proline biosynthesis

We propose a signaling pathway in which cell-extracellular matrix (ECM) adhesion components PINCH-1 and kindlin-2 sense mechanical signals from ECM and link them to proline biosynthesis, a vital metabolic pathway for macromolecule synthesis, redox balance, and ECM remodeling. ECM stiffening promotes PINCH-1 expression via integrin signaling, which suppresses dynamin-related protein 1 (DRP1) expression and mitochondrial fission, resulting in increased kindlin-2 translocation into mitochondria and interaction with Δ¹ -pyrroline-5-carboxylate (P5C) reductase 1 (PYCR1). Kindlin-2 interaction with PYCR1 protects the latter from proteolytic degradation, leading to elevated PYCR1 level. Additionally, PINCH-1 promotes P5C synthase (P5CS) expression and P5C synthesis, which, together with increased PYCR1 level, support augmented proline biosynthesis. This signaling pathway is frequently activated in fibrosis and cancer, resulting in increased proline biosynthesis and excessive collagen matrix production, which in turn further promotes ECM stiffening. Targeting this signaling pathway, therefore, may provide an effective strategy for alleviating fibrosis and cancer progression.

A Potential Role for Integrin-Linked Kinase in Colorectal Cancer Growth and Progression via Regulating Senescence and Immunity

Integrin-linked kinase (ILK) has been implicated as a molecular driver and mediator in both inflammation and tumorigenesis of the colon. ILK functions as an adaptor and mediator protein linking the extracellular matrix with downstream signaling pathways. ILK is broadly expressed in many human tissues and cells. It is also overexpressed in many cancers, including colorectal cancer (CRC). Inflammation, as evidenced by inflammatory bowel disease (IBD), is one of the highest risk factors for initiating CRC. This has led to the hypothesis that targeting ILK therapeutically could have potential in CRC, as it regulates different cellular processes associated with CRC development and progression as well as inflammation in the colon. A number of studies have indicated an ILK function in senescence, a cellular process that arrests the cell cycle while maintaining active metabolism and transcription. Senescent cells produce different secretions collectively known as the senescence-associated secretory phenotype (SASP). The SASP secretions influence infiltration of different immune cells, either positively for clearing senescent cells or negatively for promoting tumor growth, reflecting the dual role of senescence in cancer. However, a role for ILK in senescence and immunity in CRC remains to be determined. In this review, we discuss the possible role for ILK in senescence and immunity, paying particular attention to the relevance of ILK in CRC. We also examine how activating Toll-like receptors (TLRs) and their agonists in CRC could trigger immune responses against cancer, as a combination therapy with ILK inhibition.

Tyro3, Axl, Mertk receptor-mediated efferocytosis and immune regulation in the tumor environment

Three structurally related tyrosine receptor cell surface kinases, Tyro3, Axl, and Mertk (TAM) have been recognized to modulate immune function, tissue homeostasis, cardiovasculature, and cancer. The TAM receptor family appears to operate in adult mammals across multiple cell types, suggesting both widespread and specific regulation of cell functions and immune niches. TAM family members regulate tissue homeostasis by monitoring the presence of phosphatidylserine expressed on stressed or apoptotic cells. The detection of phosphatidylserine on apoptotic cells requires intermediary molecules that opsonize the dying cells and tether them to TAM receptors on phagocytes. This complex promotes the engulfment of apoptotic cells, also known as efferocytosis, that leads to the resolution of inflammation and tissue healing. The immune mechanisms dictating these processes appear to fall upon specific family members or may involve a complex of different receptors acting cooperatively to resolve and repair damaged tissues. Here, we focus on the role of TAM receptors in triggering efferocytosis and its consequences in the regulation of immune responses in the context of inflammation and cancer.

A mechanoresponsive PINCH-1-Notch2 interaction regulates smooth muscle differentiation of human placental mesenchymal stem cells

Extracellular matrix (ECM) stiffness plays an important role in the decision making process of smooth muscle differentiation of mesenchymal stem cells (MSCs) but the underlying mechanisms are incompletely understood. Here we show that a signaling axis consisting of PINCH-1 and Notch2 is critically involved in mediating the effect of ECM stiffness on smooth muscle differentiation of MSCs. Notch2 level is markedly increased in ECM stiffness-induced smooth muscle differentiation of human placental MSCs. Knockdown of Notch2 from human placental MSCs effectively inhibits ECM stiffness-induced smooth muscle differentiation, whereas overexpression of North intracellular domain (NICD2) is sufficient to drive human placental MSC differentiation toward smooth muscle cells. At the molecular level, Notch2 directly interacts with PINCH-1. The interaction of Notch2 with PINCH-1 is significantly increased in response to ECM stiffness favoring smooth muscle differentiation. Furthermore, depletion of PINCH-1 from human placental MSCs reduces Notch2 level and consequently suppresses ECM stiffness-induced smooth muscle differentiation. Re-expression of PINCH-1, but not that of a Notch2-binding defective PINCH-1 mutant, in PINCH-1 knockdown human placental MSCs restores smooth muscle differentiation. Finally, overexpression of NICD2 is sufficient to override PINCH-1 deficiency-induced defect in smooth muscle differentiation. Our results identify an ECM stiffness-responsive PINCH-1-Notch2 interaction that is critically involved in ECM stiffness-induced smooth muscle differentiation of human placental MSCs.

A Case of Lung Adenocarcinoma Harboring a Rare LOC285000-ALK-NCK2 Gene Fusion Identified by Next-Generation Sequencing With Long-Term Response to Crizotinib

Most patients with NSCLC, initially sensitive, will develop resistance after a period of time after the application of ALK inhibitors. We present here a rare LOC285000-ALK-NCK2 gene fusion with response to crizotinib treatment; the patient achieved a progression-free survival of 23 months.

Master Regulators of Muscle Atrophy: Role of Costamere Components

The loss of muscle mass and force characterizes muscle atrophy in several different conditions, which share the expression of atrogenes and the activation of their transcriptional regulators. However, attempts to antagonize muscle atrophy development in different experimental contexts by targeting contributors to the atrogene pathway showed partial effects in most cases. Other master regulators might independently contribute to muscle atrophy, as suggested by our recent evidence about the co-requirement of the muscle-specific chaperone protein melusin to inhibit unloading muscle atrophy development. Furthermore, melusin and other muscle mass regulators, such as nNOS, belong to costameres, the macromolecular complexes that connect sarcolemma to myofibrils and to the extracellular matrix, in correspondence with specific sarcomeric sites. Costameres sense a mechanical load and transduce it both as lateral force and biochemical signals. Recent evidence further broadens this classic view, by revealing the crucial participation of costameres in a sarcolemmal “signaling hub” integrating mechanical and humoral stimuli, where mechanical signals are coupled with insulin and/or insulin-like growth factor stimulation to regulate muscle mass. Therefore, this review aims to enucleate available evidence concerning the early involvement of costamere components and additional putative master regulators in the development of major types of muscle atrophy.

RSU-1 interaction with prohibitin-2 links cell-extracellular matrix detachment to downregulation of ERK signaling

Cell–extracellular matrix (ECM) detachment is known to decrease extracellular signal–regulated kinase (ERK) signaling, an intracellular pathway that is central for control of cell behavior. How cell–ECM detachment is linked to downregulation of ERK signaling, however, is incompletely understood. We show here that focal adhesion protein Ras Suppressor 1 (RSU1) plays a critical role in cell–ECM detachment induced suppression of ERK signaling. We have identified prohibitin 2 (PHB2), a component of membrane lipid rafts, as a novel binding protein of RSU1, and mapped a major RSU1-binding site to PHB2 amino acids 150 to 206 in the C-terminal region of the PHB/SPFH (stomatin/prohibitin/flotillin/HflKC) domain. The PHB2 binding is mediated by multiple sites located in the N-terminal leucine-rich repeat region of RSU1. Depletion of PHB2 suppressed cell–ECM adhesion–induced ERK activation. Furthermore, cell–ECM detachment increased RSU1 association with membrane lipid rafts and interaction with PHB2. Finally, knockout of RSU1 or inhibition of RSU1 interaction with PHB2 by overexpression of the major RSU1-binding PHB2 fragment (amino acids 150–206) effectively suppressed the cell–ECM detachment induced downregulation of ERK signaling. Additionally, expression of venus-tagged wild-type RSU1 restored ERK signaling, while expression of venus-tagged PHB2-binding defective RSU1 mutant in which the N-terminal leucine-rich repeat region is deleted did not. Taken together, Our findings identify a novel RSU1-PHB2 signaling axis that senses cell–ECM detachment and links it to decreased ERK signaling.

The emerging potential of SIRT-3 in oxidative stress-inflammatory axis associated increased neuroinflammatory component for metabolically impaired neural cell

People suffering from conditions like epilepsy, where there is an excess of neuron excitement, stroke, and cardiac arrest, where there are oxygen and glucose deprivation, Alzheimer, Parkinson, and Huntington's disease that causes metabolic and also oxidative stress-inflammatory axis; are known to be more vulnerable to disturbances in the metabolism, and there is a lot of inadequacy in defining the inflammation's mechanistic connections, as well as neurodegeneration and the bioenergetic deficiencies in the CNS. We retrieved relevant studies from PubMed/ScienceDirect/Medline/Public library of science/Mendeley/Springer link as well as Google Scholar. We used various keywords both individually and in combination with the literature search. 'Epidemiology of neurodegenerative disorders', 'neurodegenerative diseases associated hyper inflammation', 'Mechanism of inflammation in neuronal cell', 'Involvement of SIRTin inflammation', 'Pathogenesis of mitochondrial associated metabolic impairment in neurons', 'Reactive oxygen species-mediated mitochondrial dysfunction' were a few of the keywords used for the search. PINCH, which is a chronic neuro-inflammatory component that cannot be detected in matured neurons which are healthy, though expressed in oxidative stress inflammatory axis related tauopathy and diseases that cause neurodegeneration. We attempted to study the regulatory mechanisms that cause changes in the bioenergetics and its neuronal defects and mitochondrial subcellular localization that are PINCH protein-mediated on the other handSIRT1, the most intensively studied sirtuin, in oxidative stress-mediated inflammatory consequence for many diseases but very few research data explore the role of SIRT-3 for correction of the chronic neuroinflammatory component. Thus, in this review, we investigate the very recently identified molecules involving in the pathogenesis during stimulated oxidative stress-inflammatory axis in the excitatory neuronal cell which changes brain metabolism. Simultaneously, in CNS neurons of diseases with a component of chronic neuroinflammation which exhibit neuroprotective response, the consequences (mechanistic and biological) of SIRT-3, could be emerging future targets for neurodegenerative disorder treatment with impaired metabolisms.

Integrin signaling: linking mechanical stimulation to skeletal muscle hypertrophy

The α₇β₁-integrin is a transmembrane adhesion protein that connects laminin in the extracellular matrix (ECM) with actin in skeletal muscle fibers. The α₇β₁-integrin is highly expressed in skeletal muscle and is concentrated at costameres and myotendious junctions, providing the opportunity to transmit longitudinal and lateral forces across the membrane. Studies have demonstrated that α₇-integrin subunit mRNA and protein are upregulated following eccentric contractions as a mechanism to reinforce load-bearing structures and resist injury with repeated bouts of exercise. It has been hypothesized for many years that the integrin can also promote protein turnover in a manner that can promote beneficial adaptations with resistance exercise training, including hypertrophy. This review provides basic information about integrin structure and activation and then explores its potential to serve as a critical mechanosensor and activator of muscle protein synthesis and growth. Overall, the hypothesis is proposed that the α₇β₁-integrin can contribute to mechanical-load induced skeletal muscle growth via an mammalian target of rapamycin complex 1-independent mechanism.

LIMS1 Promotes Pancreatic Cancer Cell Survival under Oxygen-Glucose Deprivation Conditions by Enhancing HIF1A Protein Translation

PURPOSE

Oxygen and glucose deprivation is a common feature of the solid tumor. Regulatory network underlying the adaptation of cancer cells to the harsh microenvironment remains unclear. We determined the mechanistic role of LIM and senescent cell antigen-like-containing domain protein 1 (LIMS1) in cancer cell survival under oxygen-glucose deprivation conditions.

EXPERIMENTAL DESIGN

The expression level of LIMS1 was determined by IHC staining and analyzing the mRNA expression profiles from The Cancer Genome Atlas of three human solid tumors. Roles of LIMS1 in cancer cell metabolism and growth were determined by molecular and cell biology methods. A jetPEI nanocarrier was used as the vehicle for anti-LIMS1 siRNAs in mouse models of cancer therapeutics.

RESULTS

LIMS1 expression was drastically elevated in pancreatic ductal adenocarcinoma (PDAC). High LIMS1 level was associated with advanced TNM stage and poor prognosis of patients with tumor. Increased LIMS1 expression was pivotal for tumor cells to survive in the oxygen-glucose deprivation conditions. Mechanistically, LIMS1 enhanced GLUT1 expression and membrane translocation, which facilitated tumor cell adaptation to the glucose deprivation stress. Furthermore, LIMS1 promoted HIF1A protein translation by activating AKT/mTOR signaling, while hypoxia-inducible factor 1 (HIF1) transactivated LIMS1 transcription, thus forming a positive feedback loop in PDAC cell adaptation to oxygen deprivation stress. Inhibition of LIMS1 with jetPEI nanocarrier-delivered anti-LIMS1 siRNAs significantly increased cell death and suppressed tumor growth.

CONCLUSIONS

LIMS1 promotes pancreatic cancer cell survival under oxygen-glucose deprivation conditions by activating AKT/mTOR signaling and enhancing HIF1A protein translation. LIMS1 is crucial for tumor adaptation to oxygen-glucose deprivation conditions and is a promising therapeutic target for cancer treatment.

Identification of crucial genes associated with Parkinson's disease using microarray data

The present study aimed to examine potential crucial genes associated with Parkinson's disease (PD) in addition to the interactions and regulators of these genes. The chip data (GSE7621) were obtained from the Gene Expression Omnibus and standardized using the robust multi‑array average in the Affy package of R software. The differentially expressed genes (DEGs) were then screened using the Samr package with a false discovery rate (FDR) <0.05 and |log2 fold change (FC)|>1. Crucial PD‑associated genes were predicted using the Genetic Association Database in the Database for Annotation, Visualization and Integrated Discovery and sequence alignment. Furthermore, transcription factors (TFs) of the crucial PD‑associated genes were predicted, and protein‑protein interactions (PPIs) between the crucial PD‑associated genes were analyzed using the Search Tool for the Retrieval of Interacting Genes/Proteins. Additionally, another dataset of PD was used to validate the expression of crucial PD‑associated genes. A total of 670 DEGs (398 upregulated and 272 downregulated genes) were identified in the PD samples. Of these, 10 DEGs enriched in pathways associated with the nervous system were predicted to be crucial in PD, including C‑X‑C chemokine receptor type 4 (CXCR4), deleted in colorectal cancer (DCC) and NCL adaptor protein 2 (NCK2). All 10 genes were associated with neuron development and differentiation. They were simultaneously modulated by multiple TFs, including GATA, E2F and E4 promoter‑binding protein 4. The PPI networks showed that DCC and CXCR4 were hub proteins. The DCC‑netrin 1‑roundabout guidance receptor 2‑slit guidance ligand 1 interaction pathway, and several genes, including TOX high mobility group box family member 4, kinase insert domain receptor and zymogen granule protein 16B, which interacted with CXCR4, were novel findings. Additionally, CXCR4 and NCK2 were upregulated in another dataset (GSE8397) of PD. These genes, interactions of proteins and TFs may be important in the progression of PD.

Integrin-Linked Kinase Signaling Promotes Cyst Growth and Fibrosis in Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by innumerous fluid-filled cysts and progressive deterioration of renal function. Previously, we showed that periostin, a matricellular protein involved in tissue repair, is markedly overexpressed by cyst epithelial cells. Periostin promotes cell proliferation, cyst growth, interstitial fibrosis, and the decline in renal function in PKD mice. Here, we investigated the regulation of these processes by the integrin-linked kinase (ILK), a scaffold protein that links the extracellular matrix to the actin cytoskeleton and is stimulated by periostin. Pharmacologic inhibition or shRNA knockdown of ILK prevented periostin-induced Akt/mammalian target of rapamycin (mTOR) signaling and ADPKD cell proliferation in vitro Homozygous deletion of ILK in renal collecting ducts (CD) of Ilk^fl/fl ;Pkhd1-Cre mice caused tubule dilations, apoptosis, fibrosis, and organ failure by 10 weeks of age. By contrast, Ilk^fl/+ ;Pkhd1-Cre mice had normal renal morphology and function and survived >1 year. Reduced expression of ILK in Pkd1^fl/fl ;Pkhd1-Cre mice, a rapidly progressive model of ADPKD, decreased renal Akt/mTOR activity, cell proliferation, cyst growth, and interstitial fibrosis, and significantly improved renal function and animal survival. Additionally, CD-specific knockdown of ILK strikingly reduced renal cystic disease and fibrosis and extended the life of pcy/pcy mice, a slowly progressive PKD model. We conclude that ILK is critical for maintaining the CD epithelium and renal function and is a key intermediate for periostin activation of signaling pathways involved in cyst growth and fibrosis in PKD.

Molecular insights of Gas6/TAM in cancer development and therapy

Since growth arrest-specific gene 6 (Gas6) was discovered in 1988, numerous studies have highlighted the role of the Gas6 protein and its receptors Tyro3, Axl and Mer (collectively referred to as TAM), in proliferation, apoptosis, efferocytosis, leukocyte migration, sequestration and platelet aggregation. Gas6 has a critical role in the development of multiple types of cancers, including pancreatic, prostate, oral, ovarian and renal cancers. Acute myelocytic leukaemia (AML) is a Gas6-dependent cancer, and Gas6 expression predicts poor prognosis in AML. Interestingly, Gas6 also has a role in establishing tumour dormancy in the bone marrow microenvironment and in suppressing intestinal tumorigenesis. Numerous studies regarding cancer therapy have targeted Gas6 and TAM receptors with good results. However, some findings have suggested that Gas6 is associated with the development of resistance to cancer therapies. Concerning these significant effects of Gas6 in numerous cancers, we discuss the roles of Gas6 in cancer development in this review. First, we introduce basic knowledge on Gas6 and TAM receptors. Next, we describe and discuss the involvement of Gas6 and TAM receptors in cancers from different organ systems. Finally, we highlight the progress in therapies targeting Gas6 and TAM receptors. This review presents the significant roles of Gas6 in cancers from different systems and may contribute to the continued promotion of Gas6 as a therapeutic target.

Evidence for Integrin - Venus Kinase Receptor 1 Alliance in the Ovary of Schistosoma mansoni Females Controlling Cell Survival

In metazoan integrin signaling is an important process of mediating extracellular and intracellular communication processes. This can be achieved by cooperation of integrins with growth factor receptors (GFRs). Schistosoma mansoni is a helminth parasite inducing schistosomiasis, an infectious disease of worldwide significance for humans and animals. First studies on schistosome integrins revealed their role in reproductive processes, being involved in spermatogenesis and oogenesis. With respect to the roles of eggs for maintaining the parasite´s life cycle and for inducing the pathology of schistosomiasis, elucidating reproductive processes is of high importance. Here we studied the interaction of the integrin receptor Smβ-Int1 with the venus kinase receptor SmVKR1 in S. mansoni. To this end we cloned and characterized SmILK, SmPINCH, and SmNck2, three putative bridging molecules for their role in mediating Smβ-Int1/SmVKR1 cooperation. Phylogenetic analyses showed that these molecules form clusters that are specific for parasitic platyhelminths as it was shown for integrins before. Transcripts of all genes colocalized in the ovary. In Xenopus oocytes germinal vesicle breakdown (GVBD) was only induced if all members were simultaneously expressed. Coimmunoprecipitation results suggest that a Smβ-Int1-SmILK-SmPINCH-SmNck2-SmVKR1 complex can be formed leading to the phosphorylation and activation of SmVKR1. These results indicate that SmVKR1 can be activated in a ligand-independent manner by receptor-complex interaction. RNAi and inhibitor studies to knock-down SmILK as a representative complex member concurrently revealed effects on the extracellular matrix surrounding the ovary and oocyte localization within the ovary, oocyte survival, and egg production. By TUNEL assays, confocal laser scanning microscopy (CLSM), Caspase-3 assay, and transcript profiling of the pro-apoptotic BCL-2 family members BAK/BAX we obtained first evidence for roles of this signaling complex in mediating cell death in immature and primary oocytes. These results suggest that the Smβ-Int1/SmVKR1 signaling complex is important for differentiation and survival in oocytes of paired schistosomes.

Parasites of the genus Schistosoma cause schistosomiasis, a life-threatening infectious disease for humans and animals worldwide. Among the remarkable biological features of schistosomes is the differentiation of the female gonads which is controlled by pairing with the male and a prerequisite for egg production. Eggs, however, are not only important for the maintenance of the life-cycle; they also cause the pathological consequences of schistosomiasis. Part of the eggs gets trapped in host tissues such as liver and spleen and trigger inflammatory processes, finally leading to liver cirrhosis. Research activities of the last decade have indicated that different families of cellular and receptor-type kinases but also integrins contribute to the control of mitogenic activity and differentiation the female goands. In this context an unusual class of receptor tyrosine kinases (RTKs) has been identified, the venus kinase receptors (SmVKRs). By biochemical and molecular approaches we demonstrate that SmVKR1 activation can be achieved by cooperation with a signaling complex consisting of the beta integrin receptor Smβ-Int1 and the bridging molecules SmILK, SmPINCH, SmNck2. Besides unravelling a novel way of SmVKR1 activation, we provide evidence that this complex controls the differentiation status of oocytes by regulating cell death-associated processes.

Signaling via PINCH: Functions, binding partners and implications in human diseases

Particularly interesting new cysteine-histidine-rich protein (PINCH) is a LIM-domain-only adaptor that plays important roles in cytoskeletal organization and extracellular matrix adhesion, migration, proliferation and survival. Mammalian cells have two functional PINCH proteins, PINCH1 and PINCH2. PINCH not only binds to Nck2 and engages in the signaling of growth factor receptors, but also forms a ternary complex with ILK and parvin (IPP complex). Normally, the IPP complex locates to focal adhesions participating in the signaling of integrins and mediating the interaction of cytoskeleton and extracellular matrix (ECM). Accumulative evidence indicates that abnormalities in PINCH signaling are involved in the pathogenesis of important diseases, such as cancers, renal diseases, cardiomyopathy, and HIV. Therefore, clarifying the functions of PINCH and its interactions with key factors is important for better understanding of signaling events both in health and disease.

ILK-PI3K/AKT pathway participates in cutaneous wound contraction by regulating fibroblast migration and differentiation to myofibroblast

The interactions between fibroblasts and the extracellular matrix in wound contraction are mainly mediated via integrin signaling. Integrin-linked kinase (ILK) is a key mediator in integrin signal transduction. We investigated the role of ILK in cutaneous wound contraction. We found that ILK was involved in cutaneous wound healing in rats, and ILK and PI3K/AKT inhibitors inhibited wound contraction and re-epithelialization, consequently delaying wound healing in vivo. Further, using in vitro studies, we demonstrated that ILK and PI3K/AKT inhibitors suppressed the contraction of fibroblast-populated collagen lattices, inhibited fibroblast migration, and interrupted the effect of TGF-β1 on promoting alpha smooth muscle actin (α-SMA) expression in fibroblasts. When ILK expression was directly blocked by ILK small interfering RNA transfection, the migration and α-SMA expression of normal dermal fibroblasts were significantly suppressed as well. The data suggest that the ILK-PI3K/AKT signaling pathway mediates cutaneous wound contraction by regulating fibroblast migration and differentiation to myofibroblasts.

Actin remodeling by Nck regulates endothelial lumen formation

Nck-dependent actin remodeling enables endothelial morphogenesis by promoting cell elongation and proper organization of VE-cadherin intercellular junctions. Nck determines spatiotemporal patterns of Cdc42/aPKC activation to regulate endothelial apical-basal polarity and lumen formation.

Multiple angiogenic cues modulate phosphotyrosine signaling to promote vasculogenesis and angiogenesis. Despite its functional and clinical importance, how vascular cells integrate phosphotyrosine-dependent signaling to elicit cytoskeletal changes required for endothelial morphogenesis remains poorly understood. The family of Nck adaptors couples phosphotyrosine signals with actin dynamics and therefore is well positioned to orchestrate cellular processes required in vascular formation and remodeling. Culture of endothelial cells in three-dimensional collagen matrices in the presence of VEGF stimulation was combined with molecular genetics, optical imaging, and biochemistry to show that Nck-dependent actin remodeling promotes endothelial cell elongation and proper organization of VE-cadherin intercellular junctions. Major morphogenetic defects caused by abrogation of Nck signaling included loss of endothelial apical-basal polarity and impaired lumenization. Time-lapse imaging using a Förster resonance energy transfer biosensor, immunostaining with phospho-specific antibodies, and GST pull-down assays showed that Nck determines spatiotemporal patterns of Cdc42/aPKC activation during endothelial morphogenesis. Our results demonstrate that Nck acts as an important hub integrating angiogenic cues with cytoskeletal changes that enable endothelial apical-basal polarization and lumen formation. These findings point to Nck as an emergent target for effective antiangiogenic therapy.

Transcriptional Response to Acute Thermal Exposure in Juvenile Chinook Salmon Determined by RNAseq

Thermal exposure is a serious and growing challenge facing fish species worldwide. Chinook salmon (Oncorhynchus tshawytscha) living in the southern portion of their native range are particularly likely to encounter warmer water due to a confluence of factors. River alterations have increased the likelihood that juveniles will be exposed to warm water temperatures during their freshwater life stage, which can negatively impact survival, growth, and development and pose a threat to dwindling salmon populations. To better understand how acute thermal exposure affects the biology of salmon, we performed a transcriptional analysis of gill tissue from Chinook salmon juveniles reared at 12° and exposed acutely to water temperatures ranging from ideal to potentially lethal (12° to 25°). Reverse-transcribed RNA libraries were sequenced on the Illumina HiSeq2000 platform and a de novo reference transcriptome was created. Differentially expressed transcripts were annotated using Blast2GO and relevant gene clusters were identified. In addition to a high degree of downregulation of a wide range of genes, we found upregulation of genes involved in protein folding/rescue, protein degradation, cell death, oxidative stress, metabolism, inflammation/immunity, transcription/translation, ion transport, cell cycle/growth, cell signaling, cellular trafficking, and structure/cytoskeleton. These results demonstrate the complex multi-modal cellular response to thermal stress in juvenile salmon.

The focal adhesion protein PINCH-1 associates with EPLIN at integrin adhesion sites

PINCH-1 is a LIM-only domain protein that forms a ternary complex with integrin-linked kinase (ILK) and parvin (to form the IPP complex) downstream of integrins. Here, we demonstrate that PINCH-1 (also known as Lims1) gene ablation in the epidermis of mice caused epidermal detachment from the basement membrane, epidermal hyperthickening and progressive hair loss. PINCH-1-deficient keratinocytes also displayed profound adhesion, spreading and migration defects in vitro that were substantially more severe than those of ILK-deficient keratinocytes indicating that PINCH-1 also exerts functions in an ILK-independent manner. By isolating the PINCH-1 interactome, the LIM-domain-containing and actin-binding protein epithelial protein lost in neoplasm (EPLIN, also known as LIMA1) was identified as a new PINCH-1-associated protein. EPLIN localized, in a PINCH-1-dependent manner, to integrin adhesion sites of keratinocytes in vivo and in vitro and its depletion severely attenuated keratinocyte spreading and migration on collagen and fibronectin without affecting PINCH-1 levels in focal adhesions. Given that the low PINCH-1 levels in ILK-deficient keratinocytes were sufficient to recruit EPLIN to integrin adhesions, our findings suggest that PINCH-1 regulates integrin-mediated adhesion of keratinocytes through the interactions with ILK as well as EPLIN.

Rsu1 contributes to cell adhesion and spreading in MCF10A cells via effects on P38 map kinase signaling

The ILK, PINCH, Parvin (IPP) complex regulates adhesion and migration via binding of ILK to β1 integrin and α−parvin thus linking focal adhesions to actin cytoskeleton. ILK also binds the adaptor protein PINCH which connects signaling proteins including Rsu1 to the complex. A recent study of Rsu1 and PINCH1 in non-transformed MCF10A human mammary epithelial cells revealed that the siRNA-mediated depletion of either Rsu1 or PINCH1 decreased the number of focal adhesions (FAs) and altered the distribution and localization of FA proteins. This correlated with reduced adhesion, failure to spread or migrate in response to EGF and a loss of actin stress fibers and caveolae. The depletion of Rsu1 caused significant reduction in PINCH1 implying that Rsu1 may function in part by regulating levels of PINCH1. However, Rsu1, but not PINCH1, was required for EGF-induced activation of p38 Map kinase and ATF2 phosphorylation, suggesting a Rsu1 function independent from the IPP complex. Reconstitution of Rsu1-depleted cells with a Rsu1 mutant (N92D) that does not bind to PINCH1 failed to restore FAs or migration but did promote IPP-independent spreading and constitutive as well as EGF-induced p38 activation. In this commentary we discuss p38 activity in adhesion and how Rsu1 expression may be linked to Map kinase kinase (MKK) activation and detachment-induced stress kinase signaling.

The integrin-linked kinase-PINCH-parvin complex supports integrin αIIbβ3 activation

Integrin-linked kinase (ILK) is an important signaling regulator that assembles into the heteroternary complex with adaptor proteins PINCH and parvin (termed the IPP complex). We recently reported that ILK is important for integrin activation in a Chinese hamster ovary (CHO) cell system. We previously established parental CHO cells expressing a constitutively active chimeric integrin (αIIbα6Bβ3) and mutant CHO cells expressing inactive αIIbα6Bβ3 due to ILK deficiency. In this study, we further investigated the underlying mechanisms for ILK-dependent integrin activation. ILK-deficient mutant cells had trace levels of PINCH and α-parvin, and transfection of ILK cDNA into the mutant cells increased not only ILK but also PINCH and α-parvin, resulting in the restoration of αIIbα6Bβ3 activation. In the parental cells expressing active αIIbα6Bβ3, ILK, PINCH, and α-parvin were co-immunoprecipitated, indicating the formation of the IPP complex. Moreover, short interfering RNA (siRNA) experiments targeting PINCH-1 or both α- and β-parvin mRNA in the parent cells impaired the αIIbα6Bβ3 activation as well as the expression of the other components of the IPP complex. In addition, ILK mutants possessing defects in either PINCH or parvin binding failed to restore αIIbα6Bβ3 activation in the mutant cells. Kindlin-2 siRNA in the parental cells impaired αIIbα6Bβ3 activation without disturbing the expression of ILK. For CHO cells stably expressing wild-type αIIbβ3 that is an inactive form, overexpression of a talin head domain (THD) induced αIIbβ3 activation and the THD-induced αIIbβ3 activation was impaired by ILK siRNA through a significant reduction in the expression of the IPP complex. In contrast, overexpression of all IPP components in the αIIbβ3-expressing CHO cells further augmented THD-induced αIIbβ3 activation, whereas they did not induce αIIbβ3 activation without THD. These data suggest that the IPP complex rather than ILK plays an important role and supports integrin activation probably through stabilization of the active conformation.

Phosphatase of regenerating liver 3 (PRL3) provokes a tyrosine phosphoproteome to drive prometastatic signal transduction

Phosphatase of regenerating liver 3 (PRL3) is suspected to be a causative factor toward cellular metastasis when in excess. To date, the molecular basis for PRL3 function remains an enigma, making efforts at distilling a concerted mechanism for PRL3-mediated metastatic dissemination very difficult. We previously discovered that PRL3 expressing cells exhibit a pronounced increase in protein tyrosine phosphorylation. Here we take an unbiased mass spectrometry-based approach toward identifying the phosphoproteins exhibiting enhanced levels of tyrosine phosphorylation with a goal to define the "PRL3-mediated signaling network." Phosphoproteomic data support intracellular activation of an extensive signaling network normally governed by extracellular ligand-activated transmembrane growth factor, cytokine, and integrin receptors in the PRL3 cells. Additionally, data implicate the Src tyrosine kinase as the major intracellular kinase responsible for "hijacking" this network and provide strong evidence that aberrant Src activation is a major consequence of PRL3 overexpression. Importantly, the data support a PDGF(α/β)-, Eph (A2/B3/B4)-, and Integrin (β1/β5)-receptor array as being the predominant network coordinator in the PRL3 cells, corroborating a PRL3-induced mesenchymal-state. Within this network, we find that tyrosine phosphorylation is increased on a multitude of signaling effectors responsible for Rho-family GTPase, PI3K-Akt, STAT, and ERK activation, linking observations made by the field as a whole under Src as a primary signal transducer. Our phosphoproteomic data paint the most comprehensive picture to date of how PRL3 drives prometastatic molecular events through Src activation.

PINCH expression in relation to radiation response in co-cultured colon cancer cells and in rectal cancer patients

Particularly interesting new cysteine-histidine rich protein (PINCH), involved in cell spreading, motility and proliferation, has been shown to enhance radioresistance in colon cancer cell lines. The expression of PINCH in relation to radiation was studied in co-cultured colon cancer cells. Furthermore, the clinical significance between PINCH and radiotherapy (RT) was analyzed in rectal cancer patients with or without RT. The relative PINCH expression in colon cancer (KM12C) cells cultured separately and in co-culture was examined by western blotting and real-time PCR, and was analyzed over a period of 8 and 24 h after radiation. PINCH expression was immunohistochemically examined in 137 primary rectal tumors for which 65 cases did not receive RT and 72 cases received RT. PINCH expression tended to decrease from that in the separately cultured KM12C cells without radiation to that in cells with radiation at 8 h (P=0.060); while in the co-cultured cells, no significant difference was found (P=0.446). In patients with RT, strong PINCH expression was related to worse survival, when compared to patients with weak expression, independent of TNM stage, degree of differentiation, age and p53 status (P=0.029, RR 4.03, 95% CI 1.34‑12.1). No survival relationship for the patients without RT was observed (P=0.287). A statistical interaction analysis between PINCH, RT and survival showed a trend towards significance (P=0.057). In conclusion, PINCH predicts survival in rectal cancer patients with RT, but not in patients without RT. The expression of PINCH may be regulated by radiation and by environmental factors surrounding the cells.

Rsu1 contributes to regulation of cell adhesion and spreading by PINCH1-dependent and - independent mechanisms

Cell adhesion and migration are complex processes that require integrin activation, the formation and dissolution of focal adhesion (FAs), and linkage of actin cytoskeleton to the FAs. The IPP (ILK, PINCH, Parvin) complex regulates FA formation via binding of the adaptor protein ILK to β1 integrin, PINCH and parvin. The signaling protein Rsu1 is linked to the complex via binding PINCH1. The role of Rsu1 and PINCH1 in adhesion and migration was examined in non-transformed mammary epithelial cells. Confocal microscopy revealed that the depletion of either Rsu1 or PINCH1 by siRNA in MCF10A cells decreased the number of focal adhesions and altered the distribution and localization of β1 integrin, vinculin, talin and paxillin without affecting the levels of FA protein expression. This correlated with reduced adhesion, failure to spread or migrate in response to EGF and a loss of actin stress fibers and caveolae. In addition, constitutive phosphorylation of actin regulatory proteins occurred in the absence of PINCH1. The depletion of Rsu1 caused significant reduction in PINCH1 implying that Rsu1 may function by regulating levels of PINCH1. However, while both Rsu1- or PINCH1-depleted cells retained the ability to activate adhesion signaling in response to EGF stimulation, only Rsu1 was required for EGF-induced p38 Map Kinase phosphorylation and ATF2 activation, suggesting an Rsu1 function independent from the IPP complex. Reconstitution of Rsu1-depleted cells with an Rsu1 mutant that does not bind to PINCH1 failed to restore FAs or migration but did promote spreading and constitutive p38 activation. These data show that Rsu1-PINCH1 association with ILK and the IPP complex is required for regulation of adhesion and migration but that Rsu1 has a critical role in linking integrin-induced adhesion to activation of p38 Map kinase signaling and cell spreading. Moreover, it suggests that Rsu1 may regulate p38 signaling from the IPP complex affecting other functions including survival.

Mutations in the paxillin-binding site of integrin-linked kinase (ILK) destabilize the pseudokinase domain and cause embryonic lethality in mice

Integrin-linked kinase (ILK) localizes to focal adhesions (FAs) where it regulates cell spreading, migration, and growth factor receptor signaling. Previous reports showed that overexpressed ILK in which Val(386) and Thr(387) were substituted with glycine residues (ILK-VT/GG) could neither interact with paxillin nor localize to FA in cells expressing endogenous wild-type ILK, implying that paxillin binding to ILK is required for its localization to FAs. Here, we show that introducing this mutation into the germ line of mice (ILK-VT/GG) caused vasculogenesis defects, resulting in a general developmental delay and death at around embryonic day 12.5. Fibroblasts isolated from ILK-VT/GG mice contained mutant ILK in FAs, showed normal adhesion to and spreading on extracellular matrix substrates but displayed impaired migration. Biochemical analysis revealed that VT/GG substitutions decreased ILK protein stability leading to decreased ILK levels and reduced binding to paxillin and α-parvin. Because paxillin depletion did not affect ILK localization to FAs, the embryonic lethality and the in vitro migration defects are likely due to the reduced levels of ILK-VT/GG and diminished binding to parvins.

Deletion of integrin linked kinase in endothelial cells results in defective RTK signaling caused by caveolin 1 mislocalization

Integrin linked kinase (ILK) connects the ILK-Pinch-Parvin complex with integrin adhesion sites. Because of the functional relevance of integrin-linked signaling for endothelial cell (EC) biology, we have explored this pathway in Ilk(-/-) embryonic stem (ES) cells differentiated into ECs and vessel-like structures. We have focused in particular on the mechanistic relevance of ILK-Pinch-Parvin complex-related signaling for EC development and tube formation. Our analysis revealed that the formation of vessel-like structures was strongly reduced in Ilk(-/-) ES cells and that this phenotype could be rescued by re-expression of ILK in ES cells. ECs were MACS sorted from wild-type (WT) and Ilk(-/-) ES cells and functional analysis using intracellular calcium imaging as the read-out yielded a complete lack of vascular endothelial growth factor- and epidermal growth factor-dependent responses. The possibility of a caveolin 1-related defect was investigated by transfecting WT and Ilk(-/-) ECs with a caveolin 1-EGFP fusion protein. Time-lapse microscopy showed that the prominent phenotype is due to altered dynamics of caveolin 1 and to a lack of positioning of caveolin 1 in the vicinity of the plasma membrane and that it is rescued by re-expressing ILK in the Ilk(-/-) ES cells. We also found that the defect is caused by the perturbed organization of microtubules and cortical actin filaments. Thus, ILK is required as a scaffold to allow actin-microtubule interactions and correct positioning of caveolin 1 close to the plasma membrane. This is crucial for signaling compartmentalization in ECs and explains the key role of ILK for EC development and function.

Purification and SAXS analysis of the integrin linked kinase, PINCH, parvin (IPP) heterotrimeric complex

The heterotrimeric protein complex containing the integrin linked kinase (ILK), parvin, and PINCH proteins, termed the IPP complex, is an essential component of focal adhesions, where it interacts with many proteins to mediate signaling from integrin adhesion receptors. Here we conduct a biochemical and structural analysis of the minimal IPP complex, comprising full-length human ILK, the LIM1 domain of PINCH1, and the CH2 domain of α-parvin. We provide a detailed purification protocol for IPP and show that the purified IPP complex is stable and monodisperse in solution. Using small-angle X-ray scattering (SAXS), we also conduct the first structural characterization of IPP, which reveals an elongated shape with dimensions 120×60×40 Å. Flexibility analysis using the ensemble optimization method (EOM) is consistent with an IPP complex structure with limited flexibility, raising the possibility that inter-domain interactions exist. However, our studies suggest that the inter-domain linker in ILK is accessible and we detect no inter-domain contacts by gel filtration analysis. This study provides a structural foundation to understand the conformational restraints that govern the IPP complex.

Direct regulation of nephrin tyrosine phosphorylation by Nck adaptor proteins

The transmembrane protein nephrin is a key component of the kidney slit diaphragm that contributes to the morphology of podocyte foot processes through signaling to the underlying actin cytoskeleton. We have recently reported that tyrosine phosphorylation of the cytoplasmic tail of nephrin facilitates recruitment of Nck SH2/SH3 adaptor proteins and subsequent actin remodeling and that phosphorylation of the Nck binding sites on nephrin is decreased during podocyte injury. We now demonstrate that Nck directly modulates nephrin phosphorylation through formation of a signaling complex with the Src family kinase Fyn. The ability of Nck to enhance nephrin phosphorylation is compromised in the presence of a Src family kinase inhibitor and when the SH3 domains of Nck are mutated. Furthermore, induced loss of Nck expression in podocytes in vivo is associated with a rapid reduction in nephrin tyrosine phosphorylation. Our results suggest that Nck may facilitate dynamic signaling events at the slit diaphragm by promoting Fyn-dependent phosphorylation of nephrin, which may be important in the regulation of foot process morphology and response to podocyte injury.

PINCH is an independent prognostic factor in rectal cancer patients without preoperative radiotherapy--a study in a Swedish rectal cancer trial of preoperative radiotherapy

Background

The clinical significance between particularly interesting new cysteine-histidine rich protein (PINCH) expression and radiotherapy (RT) in tumours is not known. In this study, the expression of PINCH and its relationship to RT, clinical, pathological and biological factors were studied in rectal cancer patients.

Methods

PINCH expression determined by immunohistochemistry was analysed at the invasive margin and inner tumour area in 137 primary rectal adenocarcinomas (72 cases without RT and 65 cases with RT). PINCH expression in colon fibroblast cell line (CCD-18 Co) was determined by western blot.

Results

In patients without RT, strong PINCH expression at the invasive margin of primary tumours was related to worse survival, compared to patients with weak expression, independent of TNM stage and differentiation (P = 0.03). No survival relationship in patients with RT was observed (P = 0.64). Comparing the non-RT with RT subgroup, there was no difference in PINCH expression in primary tumours (invasive margin (P = 0.68)/inner tumour area (P = 0.49). In patients with RT, strong PINCH expression was related to a higher grade of LVD (lymphatic vessel density) (P = 0.01)

Conclusions

PINCH expression at the invasive margin was an independent prognostic factor in patients without RT. RT does not seem to directly affect the PINCH expression.

Nck2 promotes human melanoma cell proliferation, migration and invasion in vitro and primary melanoma-derived tumor growth in vivo

Background

Nck1 and Nck2 adaptor proteins are involved in signaling pathways mediating proliferation, cytoskeleton organization and integrated stress response. Overexpression of Nck1 in fibroblasts has been shown to be oncogenic. Through the years this concept has been challenged and the consensus is now that overexpression of either Nck cooperates with strong oncogenes to transform cells. Therefore, variations in Nck expression levels in transformed cells could endorse cancer progression.

Methods

Expression of Nck1 and Nck2 proteins in various cancer cell lines at different stages of progression were analyzed by western blots. We created human primary melanoma cell lines overexpressing GFP-Nck2 and investigated their ability to proliferate along with metastatic characteristics such as migration and invasion. By western blot analysis, we compared levels of proteins phosphorylated on tyrosine as well as cadherins and integrins in human melanoma cells overexpressing or not Nck2. Finally, in mice we assessed tumor growth rate of human melanoma cells expressing increasing levels of Nck2.

Results

We found that expression of Nck2 is consistently increased in various metastatic cancer cell lines compared with primary counterparts. Particularly, we observed significant higher levels of Nck2 protein and mRNA, as opposed to no change in Nck1, in human metastatic melanoma cell lines compared with non-metastatic melanoma and normal melanocytes. We demonstrated the involvement of Nck2 in proliferation, migration and invasion in human melanoma cells. Moreover, we discovered that Nck2 overexpression in human primary melanoma cells correlates with higher levels of proteins phosphorylated on tyrosine residues, assembly of Nck2-dependent pY-proteins-containing molecular complexes and downregulation of cadherins and integrins. Importantly, we uncovered that injection of Nck2-overexpressing human primary melanoma cells into mice increases melanoma-derived tumor growth rate.

Conclusions

Collectively, our data indicate that Nck2 effectively influences human melanoma phenotype progression. At the molecular level, we propose that Nck2 in human primary melanoma promotes the formation of molecular complexes regulating proliferation and actin cytoskeleton dynamics by modulating kinases or phosphatases activities that results in increased levels of proteins phosphorylated on tyrosine residues. This study provides new insights regarding cancer progression that could impact on the therapeutic strategies targeting cancer.

p21-Activated kinase 3 (PAK3) protein regulates synaptic transmission through its interaction with the Nck2/Grb4 protein adaptor

Mutations in the p21-activated kinase 3 gene (pak3) are responsible for nonsyndromic forms of mental retardation. Expression of mutated PAK3 proteins in hippocampal neurons induces abnormal dendritic spine morphology and long term potentiation anomalies, whereas pak3 gene invalidation leads to cognitive impairments. How PAK3 regulates synaptic plasticity is still largely unknown. To better understand how PAK3 affects neuronal synaptic plasticity, we focused on its interaction with the Nck adaptors that play a crucial role in PAK signaling. We report here that PAK3 interacts preferentially with Nck2/Grb4 in brain extracts and in transfected cells. This interaction is independent of PAK3 kinase activity. Selective uncoupling of the Nck2 interactions in acute cortical slices using an interfering peptide leads to a rapid increase in evoked transmission to pyramidal neurons. The P12A mutation in the PAK3 protein strongly decreases the interaction with Nck2 but only slightly with Nck1. In transfected hippocampal cultures, expression of the P12A-mutated protein has no effect on spine morphogenesis or synaptic density. The PAK3-P12A mutant does not affect synaptic transmission, whereas the expression of the wild-type PAK3 protein decreases the amplitude of spontaneous miniature excitatory currents. Altogether, these data show that PAK3 down-regulates synaptic transmission through its interaction with Nck2.

Neuronal PINCH is regulated by TNF-α and is required for neurite extension

During HIV infection of the CNS, neurons are damaged by viral proteins, such as Tat and gp120, or by inflammatory factors, such as TNF-α, that are released from infected and/or activated glial cells. Host responses to this damage may include the induction of survival or repair mechanisms. In this context, previous studies report robust expression of a protein called particularly interesting new cysteine histidine-rich protein (PINCH), in the neurons of HIV patients' brains, compared with nearly undetectable levels in HIV-negative individuals (Rearden et al., J Neurosci Res 86:2535-2542, 2008), suggesting PINCH's involvement in neuronal signaling during HIV infection of the brain. To address potential triggers for PINCH induction in HIV patients' brains, an in vitro system mimicking some aspects of HIV infection of the CNS was utilized. We investigated neuronal PINCH expression, subcellular distribution, and biological consequences of PINCH sequestration upon challenge with Tat, gp120, and TNF-α. Our results indicate that in neurons, TNF-α stimulation increases PINCH expression and changes its subcellular localization. Furthermore, PINCH mobility is required to maintain neurite extension upon challenge with TNF-α. PINCH may function as a neuron-specific host-mediated response to challenge by HIV-related factors in the CNS.

[A uNick protein]

Nck is an adaptor protein composed of three N-terminal Src Homology (SH) 3 domains followed by a unique C‑terminal SH2 domain. Like other SH2/SH3 domains-containing adaptor proteins, Nck mediates signal transduction from activated cell surface receptors by directing the flow of information to elicit properly orchestrated cell responses. In this way, Nck appears to be unique in its contribution to a wide variety of cellular processes. Moreover, in addition to the typical signal/pY-SH2/SH3-effectors mode of signaling, Nck also transduces signals through an inverse mode of -signaling (signal-SH3/SH2-pY/effectors) and from various cell compartments. Since Nck contributes to important morphogenic and mitogenic processes, deregulated expression of Nck could be detrimental to cellular homeostasis. In agreement, Nck expression has been found upregulated in numerous types of cancer. In this paper we delineate the main molecular -signaling -complexes associated with Nck, focusing on those involved in cancer progression.

SKAP2, a novel target of HSF4b, associates with NCK2/F-actin at membrane ruffles and regulates actin reorganization in lens cell

In addition to roles in stress response, heat shock factors (HSFs) play crucial roles in differentiation and development. Heat shock transcription factor 4 (HSF4) deficiency leads to defect in lens epithelial cell (LEC) differentiation and cataract formation. However, the mechanism remains obscure. Here, we identified Src kinase-associated phosphoprotein 2 (SKAP2) as a downstream target of HSF4b and it was highly expressed at the anterior tip of lens elongating fibre cells in vivo. The HSF4-deficient lenses showed reduced SKAP2 expression and defects in actin reorganization. The disassembly of stress fibres and formation of cortical actin fibres are critical for the initiation of LEC differentiation. SKAP2 localized at actin-rich ruffles in human LECs (SRA01/04 cells) and knockdown SKAP2 using RNA interference impaired the disassembly of cellular stress fibres in response to fibroblast growth factor (FGF)-b. Overexpression of SKAP2, but not the N-terminal deletion mutant of SKAP2, induced the actin remodelling. We further found that SKAP2 interacted with the SH2 domain of non-catalytic region of tyrosine kinase adaptor protein 2 (NCK2) via its N-terminus. The complex of SKAP2-NCK2-F-actin accumulated at the leading edge of the lamellipodium, where FGF receptors and focal adhesion were also recruited. These results revealed an essential role for HSF4-mediated SKAP2 expression in the regulation of actin reorganization during lens differentiation, likely through a mechanism that SKAP2 anchors the complex of NCK2/focal adhesion to FGF receptors at the lamellipodium in lens epithelial cells.

Particularly interesting cysteine- and histidine-rich protein in cardiac development and remodeling

Integrin-mediated cell-extracellular matrix interaction plays key roles in tissue morphogenesis and integrity. The Lin11-Isl-1-Mec-3 (LIM) domain-only particularly interesting cysteine- and histidine-rich (PINCH) protein functions as an adaptor essential for the assembly and function of the focal adhesion complex that links integrin signaling to the cytoskeleton and other intracellular signaling pathways and regulates diverse cellular processes such as cell adhesion, migration, growth, differentiation, and survival. Recent biochemical and genetic studies have greatly advanced our knowledge surrounding the molecular interactions and functions of each component of the focal adhesion complex and revealed a requirement for PINCH in early embryogenesis, in morphogenesis of the neural crest and cardiac outflow, and in myocardial growth and remodeling. In this review article, we will provide an overview of the current knowledge of the molecular interactions of PINCH with other components of focal adhesions, highlighting recent discoveries of the in vivo role of PINCH and discuss its potential implication for human heart disease.

The adaptor protein Nck2 mediates Slit1-induced changes in cortical neuron morphology

Slits are multifunctional guidance cues, capable of triggering neurite repulsion, extension, or branching, depending on cell type and developmental context. While the Robo family of Slit receptors is a well-established mediator of axon repulsion, a role for Robos in Slit-mediated neurite growth and branching is not well defined, and the signaling molecules that link Robo to the cytoskeletal changes that drive neurite outgrowth are not well characterized in vertebrates. We show that Slit stimulates cortical dendrite branching, and we report that Slit also triggers a robust increase in the length of cortical axons in vitro. Moreover, neurons derived from Robo1; Robo2 deficient mice do not display an increase in neurite length, indicating that endogenous Robos mediate Slit's growth-promoting effects on both axons and dendrites. We also demonstrate that the SH2/SH3 adaptor proteins Nck1 and Nck2 bind to Robo via an atypical SH3-mediated mechanism. Furthermore, we show that only Nck2 is required for the Slit-induced changes in cortical neuron morphology in vitro. These findings indicate a specific role for Nck2 in linking Robo activation to the cytoskeleton rearrangements that shape cortical neuron morphology.

How integrins control mammary epithelial differentiation: a possible role for the ILK-PINCH-Parvin complex

Differentiation into tissue-specific cell types occurs in response to numerous external signals. Integrins impart signals from the extracellular matrix microenvironment that are required for cell differentiation. However, the precise cytoplasmic transducers of these signals are yet to be understood properly. In lactating mammary epithelial cells, integrin-linked kinase has been identified as an indispensable integrin-signalling adaptor that enables the activation of Rac1, which is necessary for prolactin-induced milk protein expression. Here we use examples from various tissues to summarise possible mechanisms by which ILK and its binding partners PINCH and Parvin (ILK-PINCH-Parvin complex) could be required for Rac activation and mammary epithelial differentiation.

Impact of PINCH expression on survival in colorectal cancer patients

Background

The adaptor protein PINCH is overexpressed in the stroma of several types of cancer, and is an independent prognostic marker in colorectal cancer. In this study we further investigate the relationship of PINCH and survival regarding the response to chemotherapy in colorectal cancer.

Results

Paraffin-embedded tissue sections from 251 primary adenocarcinomas, 149 samples of adjacent normal mucosa, 57 samples of distant normal mucosa and 75 lymph node metastases were used for immunohistochemical staining. Stromal staining for PINCH increased from normal mucosa to primary tumour to metastasis. Strong staining in adjacent normal mucosa was related to worse survival independently of sex, age, tumour location, differentiation and stage (p = 0.044, HR, 1.60, 95% CI, 1.01-2.52). PINCH staining at the invasive margin tended to be related to survival (p = 0.051). In poorly differentiated tumours PINCH staining at the invasive margin was related to survival independently of sex, age and stage (p = 0.013, HR, 1.90, 95% CI, 1.14-3.16), while in better differentiated tumours it was not. In patients with weak staining, adjuvant chemotherapy was related to survival (p = 0.010, 0.013 and 0.013 in entire tumour area, invasive margin and inner tumour area, respectively), but not in patients with strong staining. However, in the multivariate analysis no such relationship was seen.

Conclusions

PINCH staining in normal adjacent mucosa was related to survival. Further, PINCH staining at the tumour invasive margin was related to survival in poorly differentiated tumours but not in better differentiated tumours, indicating that the impact of PINCH on prognosis was dependent on differentiation status.

PINCH: More than just an adaptor protein in cellular response

Particularly interesting new cysteine-histidine-rich protein (PINCH) is a LIM-domain-only adaptor protein involved in protein recruitment, subsequent assembly of multi-protein complexes, and subcellular localization of these complexes. PINCH is developmentally regulated and its expression is critical for proper cytoskeletal organization and extracellular matrix adhesion. Although PINCH has no catalytic abilities, the PIP (PINCH-ILK-parvin) complex serves as a link between integrins and components of growth factor receptor kinase and GTPase signaling pathways. Accordingly, PINCH-mediated signaling induces cell migration, spreading, and survival. Further research on the signaling cascades affected by PINCH is key to appreciating its biological significance in cell fate and systems maintenance, as the developmental functions of PINCH may extend to disease states and the cellular response to damage. PINCH is implicated in a diverse array of diseases including renal failure, cardiomyopathy, nervous system degeneration and demyelination, and tumorigenesis. This review presents evidence for PINCH's structural and functional importance in normal cellular processes and in pathogenesis. The current data for PINCH expression in nervous system disease is substantial, but due to the complex and ubiquitous nature of this protein, our understanding of its function in pathology remains unclear. In this review, an overview of studies identifying PINCH binding partners, their molecular interactions, and the potentially overlapping role(s) of PINCH in cancer and in nervous system diseases will be discussed. Many questions remain regarding PINCH's role in cells. What induces cell-specific PINCH expression? How does PINCH expression contribute to cell fate in the central nervous system? More broadly, is PINCH expression in disease a good thing? Clarifying the ambiguous functions of PINCH expression in the central nervous system and other systems is important to understand more clearly signaling events both in health and disease.

PINCH1 is transcriptional regulator in podocytes that interacts with WT1 and represses podocalyxin expression

BACKGROUND

PINCH1, an adaptor protein containing five LIM domains, plays an important role in regulating the integrin-mediated cell adhesion, migration and epithelial-mesenchymal transition. PINCH1 is induced in the fibrotic kidney after injury, and it primarily localizes at the sites of focal adhesion. Whether it can translocate to the nucleus and directly participate in gene regulation is completely unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Using cultured glomerular podocytes as a model system, we show that PINCH1 expression was induced by TGF-β1, a fibrogenic cytokine that promotes podocyte dysfunction. Interestingly, increased PINCH1 not only localized at the sites of focal adhesions, but also underwent nuclear translocation after TGF-β1 stimulation. This nuclear translocation of PINCH1 was apparently dependent on the putative nuclear export/localization signals (NES/NLS) at its C-terminus, as deletion or site-directed mutations abolished its nuclear shuttling. Co-immunoprecipitation and pull-down experiments revealed that PINCH1 interacted with Wilms tumor 1 protein (WT1), a nuclear transcription factor that is essential for regulating podocyte-specific gene expression in adult kidney. Interaction of PINCH1 and WT1 was mediated by the LIM1 domain of PINCH1 and C-terminal zinc-finger domain of WT1, which led to the suppression of the WT1-mediated podocalyxin expression in podocytes. PINCH1 also repressed podocalyxin gene transcription in a promoter-luciferase reporter assay.

CONCLUSION/SIGNIFICANCE

These results indicate that PINCH1 can shuttle into the nucleus from cytoplasm in podocytes, wherein it interacts with WT1 and suppresses podocyte-specific gene expression. Our studies reveal a previously unrecognized, novel function of PINCH1, in which it acts as a transcriptional regulator through controlling specific gene expression.

The role of the focal adhesion protein PINCH1 for the radiosensitivity of adhesion and suspension cell cultures

Focal adhesion (FA) signaling mediated by adhesion to extracellular matrix and growth factor receptors contributes to the regulation of the cellular stress response to external stimuli. Critical to focal adhesion assembly and signaling is the adapter protein PINCH1. To evaluate whether the prosurvival function of PINCH1 in radiation cell survival depends on cell adhesion, we examined PINCH1^fl/fl and PINCH1^−/− mouse embryonic fibroblasts and human cancer cell lines. Here, we found that the enhanced cellular radiosensitivity mediated by PINCH1 depletion observed under adhesion conditions is conserved when cells are irradiated under suspension conditions. This unsuspected finding could not be explained by the observed modification of adhesion and growth factor associated signaling involving FAK, Paxillin, p130^CAS, Src, AKT, GSK3β and ERK1/2 under suspension and serum withdrawal relative to adhesion conditions with serum. Our data suggest that the adapter protein PINCH1 critically participates in the regulation of the cellular radiosensitivity of normal and malignant cells similarly under adhesion and suspension conditions.