Crk at the quarter century mark: perspectives in signaling and cancer

The Multifaceted Functionality of Plasmacytoid Dendritic Cells in Gastrointestinal Cancers: A Potential Therapeutic Target?

Gastrointestinal (GI) tumors pose a significant global health burden, necessitating the exploration of novel therapeutic approaches. Plasmacytoid dendritic cells (pDCs) play a crucial role in tumor immunity, exhibiting both anti-tumor and pro-tumor effects. This review aims to summarize the role of pDCs in different types of GI tumors and assess their potential as therapeutic targets. In gastric cancer, hepatocellular carcinoma, and intrahepatic cholangiocarcinoma, increased infiltration of pDCs was associated with a worse outcome, whereas in esophageal cancer, pancreatic cancer, and colorectal cancer, pDC infiltration improved the outcome. Initial animal studies of gastric cancer and hepatocellular carcinoma showed that pDCs could be a successful therapeutic target. In conclusion, pDCs play a multifaceted role in GI tumors, influencing both anti-tumor immunity and tumor progression. Further research is needed to optimize their clinical application and explore combinatorial approaches.

The genomic landscape of pediatric renal cell carcinomas

Pediatric renal cell carcinomas (RCC) differ from their adult counterparts not only in histologic subtypes but also in clinical characteristics and outcome. However, the underlying biology is still largely unclear. For this reason, we performed whole-exome and transcriptome sequencing analyses on a cohort of 25 pediatric RCC patients with various histologic subtypes, including 10 MiT family translocation (MiT) and 10 papillary RCCs. In this cohort of pediatric RCC, we find only limited genomic overlap with adult RCC, even within the same histologic subtype. Recurrent somatic mutations in genes not previously reported in RCC were detected, such as in CCDC168, PLEKHA1, VWF, and MAP3K9. Our papillary pediatric RCCs, which represent the largest cohort to date with comprehensive molecular profiling in this age group, appeared as a distinct genomic subtype differing in terms of gene mutations and gene expression patterns not only from MiT-RCC but also from their adult counterparts.

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WES and RNA-seq of 25 pediatric RCCs with various histologic subtypes

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Detected only limited genomic overlap with adult RCC

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Revealed recurrent somatic mutations in genes not previously reported in RCC

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Discovery of a CRK-PITPNA fusion gene in a pediatric papillary RCC

T cell receptor (TCR) signaling in health and disease

Interaction of the T cell receptor (TCR) with an MHC-antigenic peptide complex results in changes at the molecular and cellular levels in T cells. The outside environmental cues are translated into various signal transduction pathways within the cell, which mediate the activation of various genes with the help of specific transcription factors. These signaling networks propagate with the help of various effector enzymes, such as kinases, phosphatases, and phospholipases. Integration of these disparate signal transduction pathways is done with the help of adaptor proteins that are non-enzymatic in function and that serve as a scaffold for various protein-protein interactions. This process aids in connecting the proximal to distal signaling pathways, thereby contributing to the full activation of T cells. This review provides a comprehensive snapshot of the various molecules involved in regulating T cell receptor signaling, covering both enzymes and adaptors, and will discuss their role in human disease.

MicroRNA-215-5p Inhibits the Proliferation and Migration of Wilm's Tumor Cells by Targeting CRK

Objective:

Wilm’s tumor is a common renal malignancy in childhood with unsatisfactory prognosis. microRNA-215-5p (miR-215-5p) has been reported as a tumor-suppressive miRNA in different types of human cancers, but rarely in the Wilm’s tumor. In light of this, we tried to investigate the regulatory role and underlying mechanism of miR-215-5p in the Wilm’s tumor.

Methods:

After sample collection and cell culture, the expression of miR-215-5p and CT10 Regulator of Kinase (CRK) was detected. Then rhabdoid tumor cell lines (formerly classified as Wilms’ tumor cell lines), G401 and WT-CLS1 cells were transfected with pcDNA3.1, pcDNA3.1-CRK, sh-NC, sh-CRK, agomir NC, miR-215-5p agomir, antagomir NC or miR-215-5p antagomir to explore the function of miR-215-5p and CRK in the Wilm’s tumor cell proliferation and migration. Moreover, the relationship between miR-215-5p and CRK was analyzed by dual luciferase reporter gene assay.

Results:

Lowly-expressed miR-215-5p and highly-expressed CRK were observed in the Wilm’s tumor tissues and cells. Transfection of pcDNA3.1-CRK or miR-215-5p antagomir could promote G401 and WT-CLS1 cell proliferation and enhance migration ability, while transfection of sh-CRK or miR-215-5p agomir led to opposite results. Additionally, miR-215-5p may bind to CRK. Moreover, transfection of pcDNA3.1-CRK in G401 and WT-CLS1 cells could partially reverse the inhibitory effect of miR-215-5p agomir on the proliferation and migration of Wilm’s tumor cells.

Conclusion:

Our study highlighted that miR-215-5p could suppress the proliferation and migration of Wilm’s tumor cells by regulating the expression of CRK, providing new ideas for molecular targeted therapy for Wilm’s tumor.

Crk and CrkL as Therapeutic Targets for Cancer Treatment

Crk and CrkL are cellular counterparts of the viral oncoprotein v-Crk. Crk and CrkL are overexpressed in many types of human cancer, correlating with poor prognosis. Furthermore, gene knockdown and knockout of Crk and CrkL in tumor cell lines suppress tumor cell functions, including cell proliferation, transformation, migration, invasion, epithelial-mesenchymal transition, resistance to chemotherapy drugs, and in vivo tumor growth and metastasis. Conversely, overexpression of tumor cells with Crk or CrkL enhances tumor cell functions. Therefore, Crk and CrkL have been proposed as therapeutic targets for cancer treatment. However, it is unclear whether Crk and CrkL make distinct or overlapping contributions to tumor cell functions in various cancer types because Crk or CrkL have been examined independently in most studies. Two recent studies using colorectal cancer and glioblastoma cells clearly demonstrated that Crk and CrkL need to be ablated individually and combined to understand distinct and overlapping roles of the two proteins in cancer. A comprehensive understanding of individual and overlapping roles of Crk and CrkL in tumor cell functions is necessary to develop effective therapeutic strategies. This review systematically discusses crucial functions of Crk and CrkL in tumor cell functions and provides new perspectives on targeting Crk and CrkL in cancer therapy.

Interferons: role in cancer therapy

Interferons (IFNs) are a group of signaling cytokines, secreted by host cells to induce protection against various disorders. IFNs can directly impact on tumor cells or indirectly induce the immune system to protect host cells. The expression levels of IFNs and its functions of are excellently modulated in a way to protect host cells from probable toxicities caused by extreme responses. The efficacy of anticancer therapies is correlated to IFNs signaling. Although IFN signaling is involved in induction of antitumor responses, chronic stimulation of the IFN signaling pathway can induce resistance to various antineoplasm therapies. Hence, IFNs are expressed by both cancer and immune cells, and modulate their biological function. Understanding this mechanism of action might be a key target of combination therapies.

Crk1/2 and CrkL play critical roles in maintaining podocyte morphology and function

Podocytes are actin-rich epithelial cells whose effacement and detachment are the main cause of glomerular disease. Crk family proteins: Crk1/2 and CrkL are reported to be important intracellular signaling proteins that are involved in many biological processes. However, the roles of them in maintaining podocyte morphology and function remain poorly understood. In this study, specific knocking down of Crk1/2 and CrkL in podocytes caused abnormal cell morphology, actin cytoskeleton rearrangement and dysfunction in cell adhesion, spreading, migration, and viability. The p130Cas, focal adhesion kinase, phosphatidylinositol 3-kinase/Akt, p38 and JNK signaling pathways involved in these alterations. Furthermore, knocking down CrkL alone conferred a more modest phenotype than did the Crk1/2 knockdown and the double knockdown. Kidney biopsy specimens from patients with focal segmental glomerulosclerosis and minimal change nephropathy showed downregulation of Crk1/2 and CrkL in glomeruli. In zebrafish embryos, Crk1/2 and CrkL knockdown compromised the morphology and caused abnormal glomerular development. Thus, our results suggest that Crk1/2 and CrkL expression are important in podocytes; loss of either will cause podocyte dysfunction, leading to foot process effacement and podocyte detachment.

CrkL is required for donor T cell migration to GvHD target organs

The success of cancer therapies based on allogeneic hematopoietic stem cell transplant relies on the ability to separate graft-versus-host disease (GvHD) from graft-versus-tumor (GVT) responses. Controlling donor T cell migration into peripheral tissues is a viable option to limit unwanted tissue damage, but a lack of specific targets limits progress on this front. Here, we show that the adaptor protein CrkL, but not the closely related family members CrkI or CrkII, is a crucial regulator of T cell migration. In vitro, CrkL-deficient T cells fail to polymerize actin in response to the integrin ligand ICAM-1, resulting in defective migration. Using a mouse model of GvHD/GVT, we found that while CrkL-deficient T cells can efficiently eliminate hematopoietic tumors they are unable to migrate into inflamed organs, such as the liver and small intestine, and thus do not cause GvHD. These results suggest a specific role for CrkL in trafficking to peripheral organs but not the lymphatic system. In line with this, we found that although CrkL-deficient T cells could clear hematopoietic tumors, they failed to clear the same tumor growing subcutaneously, highlighting the role of CrkL in controlling T cell migration into peripheral tissues. Our results define a unique role for CrkL in controlling T cell migration, and suggest that CrkL function could be therapeutically targeted to enhance the efficacy of immunotherapies involving allogeneic donor cells.

Cyclophilin A Inhibitor Debio-025 Targets Crk, Reduces Metastasis, and Induces Tumor Immunogenicity in Breast Cancer

The Crk adaptor protein, a critical modifier of multiple signaling pathways, is overexpressed in many cancers where it contributes to tumor progression and metastasis. Recently, we have shown that Crk interacts with the peptidyl prolyl cis-trans isomerase, Cyclophilin A (CypA; PP1A) via a G²¹⁹P²²⁰Y²²¹ (GPY) motif in the carboxyl-terminal linker region of Crk, thereby delaying pY221 phosphorylation and preventing downregulation of Crk signaling. Here, we investigate the physiologic significance of the CypA/Crk interaction and query whether CypA inhibition affects Crk signaling in vitro and in vivo. We show that CypA, when induced under conditions of hypoxia, regulates Crk pY221 phosphorylation and signaling in cancer cell lines. Using nuclear magnetic resonance spectroscopy, we show that CypA binds to the Crk GPY motif via the catalytic PPII domain of CypA, and small-molecule nonimmunosuppressive inhibitors of CypA (Debio-025) disrupt the CypA-CrkII interaction and restores phosphorylation of Crk Y221. In cultured cell lines, Debio-025 suppresses cell migration, and when administered in vivo in an orthotopic model of triple-negative breast cancer, Debio-025 showed antitumor efficacy either alone or in combination with anti-PD-1 mAb, reducing both tumor volume and metastatic lung dispersion. Furthermore, when analyzed by NanoString immune profiling, treatment of Debio-025 with anti-PD-1 mAb increased both T-cell signaling and innate immune signaling in tumor microenvironment. IMPLICATIONS: These data suggest that pharmacologic inhibition of CypA may provide a promising and unanticipated consequence in cancer biology, in part by targeting the CypA/CrkII axis that regulates cell migration, tumor metastasis, and host antitumor immune evasion.

ACAP4 interacts with CrkII to promote the recycling of integrin β1

ACAP4, a GTPase-activating protein (GAP) for the ADP-ribosylation factor 6 (ARF6), plays import roles in cell migration, cell polarity, vesicle trafficking and tumorigenesis. Similarly, the ubiquitously expressed adaptor protein CrkII functions in a wide range of cellular activities, including cell proliferation, T cell adhesion and activation, tumorigenesis, and bacterial pathogenesis. Here, we demonstrate that ACAP4 physically interacts with CrkII. Biochemical experiments revealed that ACAP4^550-660 and the SH3N domain of CrkII are responsible for the interaction. Functional characterization showed that the interaction is required for the recruitment of ACAP4 to the plasma membrane where ACAP4 functions to regulate the recycling of the signal transducer integrin β1. Thus, we suggest that the CrkII-ACAP4 complex may be involved in regulation of cell adhesion.

The Crk adapter protein is essential for Drosophila embryogenesis, where it regulates multiple actin-dependent morphogenic events

Small Src homology domain 2 (SH2) and 3 (SH3) adapter proteins regulate cell fate and behavior by mediating interactions between cell surface receptors and downstream signaling effectors in many signal transduction pathways. The CT10 regulator of kinase (Crk) family has tissue-specific roles in phagocytosis, cell migration, and neuronal development and mediates oncogenic signaling in pathways like that of Abelson kinase. However, redundancy among the two mammalian family members and the position of the Drosophila gene on the fourth chromosome precluded assessment of Crk's full role in embryogenesis. We circumvented these limitations with short hairpin RNA and CRISPR technology to assess Crk's function in Drosophila morphogenesis. We found that Crk is essential beginning in the first few hours of development, where it ensures accurate mitosis by regulating orchestrated dynamics of the actin cytoskeleton to keep mitotic spindles in syncytial embryos from colliding. In this role, it positively regulates cortical localization of the actin-related protein 2/3 complex (Arp2/3), its regulator suppressor of cAMP receptor (SCAR), and filamentous actin to actin caps and pseudocleavage furrows. Crk loss leads to the loss of nuclei and formation of multinucleate cells. We also found roles for Crk in embryonic wound healing and in axon patterning in the nervous system, where it localizes to the axons and midline glia. Thus, Crk regulates diverse events in embryogenesis that require orchestrated cytoskeletal dynamics.

Crk adaptor proteins mediate actin-dependent T cell migration and mechanosensing induced by the integrin LFA-1

T cell entry into inflamed tissue involves firm adhesion, spreading, and migration of the T cells across endothelial barriers. These events depend on "outside-in" signals through which engaged integrins direct cytoskeletal reorganization. We investigated the molecular events that mediate this process and found that T cells from mice lacking expression of the adaptor protein Crk exhibited defects in phenotypes induced by the integrin lymphocyte function-associated antigen 1 (LFA-1), namely, actin polymerization, leading edge formation, and two-dimensional cell migration. Crk protein was an essential mediator of LFA-1 signaling-induced phosphorylation of the E3 ubiquitin ligase c-Cbl and its subsequent interaction with the phosphatidylinositol 3-kinase (PI3K) subunit p85, thus promoting PI3K activity and cytoskeletal remodeling. In addition, we found that Crk proteins were required for T cells to respond to changes in substrate stiffness, as measured by alterations in cell spreading and differential phosphorylation of the force-sensitive protein CasL. These findings identify Crk proteins as key intermediates coupling LFA-1 signals to actin remodeling and provide mechanistic insights into how T cells sense and respond to substrate stiffness.

miR-193b-Regulated Signaling Networks Serve as Tumor Suppressors in Liposarcoma and Promote Adipogenesis in Adipose-Derived Stem Cells

Well-differentiated and dedifferentiated liposarcomas (WDLS/DDLS) account for approximately 13% of all soft tissue sarcoma in adults and cause substantial morbidity or mortality in the majority of patients. In this study, we evaluated the functions of miRNA (miR-193b) in liposarcoma in vitro and in vivo Deep RNA sequencing on 93 WDLS, 145 DDLS, and 12 normal fat samples demonstrated that miR-193b was significantly underexpressed in DDLS compared with normal fat. Reintroduction of miR-193b induced apoptosis in liposarcoma cells and promoted adipogenesis in human adipose-derived stem cells (ASC). Integrative transcriptomic and proteomic analysis of miR-193b-target networks identified novel direct targets, including CRK-like proto-oncogene (CRKL) and focal adhesion kinase (FAK). miR-193b was found to regulate FAK-SRC-CRKL signaling through CRKL and FAK. miR-193b also stimulated reactive oxygen species signaling by targeting the antioxidant methionine sulfoxide reductase A to modulate liposarcoma cell survival and ASC differentiation state. Expression of miR-193b in liposarcoma cells was downregulated by promoter methylation, resulting at least in part from increased expression of the DNA methyltransferase DNMT1 in WDLS/DDLS. In vivo, miR-193b mimetics and FAK inhibitor (PF-562271) each inhibited liposarcoma xenograft growth. In summary, miR-193b not only functions as a tumor suppressor in liposarcoma but also promotes adipogenesis in ASC. Furthermore, this study reveals key tyrosine kinase and DNA methylation pathways in liposarcoma, some with immediate implications for therapeutic exploration. Cancer Res; 77(21); 5728-40. ©2017 AACR.

Crk adaptor protein promotes PD-L1 expression, EMT and immune evasion in a murine model of triple-negative breast cancer

The tumor infiltration of immune cells in solid cancers can profoundly influence host antitumor responses. In recent years, immunotherapeutic regimens, that target immune checkpoints, demonstrated significant antitumor response by increasing intra-tumoral immune cell populations, including CD8+ effector T cells. However, administration of such immune checkpoint inhibitors is largely inefficacious in inducing immunogenicity and treating breast cancer. Currently, there is a great need to better understand cell autonomous mechanisms of immune evasion in breast cancer to identify upstream therapeutic targets that increase the efficacy of immunotherapy. Here we show that Crk, an SH2 and SH3 domain-containing adaptor protein implicated in focal adhesion signaling, cell migration, and invasion, and frequently up-regulated in human cancers, has an important role in regulating the tumor immune microenvironment. Using a murine 4T1 breast adenocarcinoma model of spontaneous metastasis in immune-competent BALB/C mice, we show that genetic ablation of Crk by CRISPR-Cas9 leads to enhanced anti-tumor immune cell populations, cytotoxic effector and immune surveillance cytokines in primary tumor. Pathologically, this leads to a significant reduction in tumor growth and lung metastasis. Mechanistically, Crk KO suppresses EMT and PD-L1 expression on tumor cells and acts additively with anti-PD1 therapy to suppress tumor growth and metastasis outcomes. Taken together, these data reveal a previously un-described function of Crk adaptor protein expression in tumor cells for cell autonomous regulation of tumor immune microenvironment.

New miRNA expression abnormalities in laryngeal squamous cell carcinoma

BACKGROUND

Although the development of novel diagnostic and treatment strategies concerning laryngeal cancer is highly intensive, the survival rate remains virtually unchanged. Small non-coding RNAs appear to be very promising biomarkers - and so remain the focus of extensive investigation in laryngeal cancer.

OBJECTIVE

We examined the expression of five miRNA and five genes related to cancer whether they could be potential laryngeal cancer biomarkers.

METHODS

We performed an analysis in 47 patients diagnosed with laryngeal cancer. The qPCR technique was used to investigate the expression profile.

RESULTS

While miR-21-3p and miR-525-5p were found to be significantly up-regulated, miR-139-3p and miR-885-5p expression is lower in laryngeal cancer. Moreover, PIK3R1 and HACE1 were found to be also down-regulated.

CONCLUSIONS

The change in miRNA expression is frequent than the expression of other tested genes. The expression of passenger strands such as miR-21-3p and miR-139-3p, which are rarely investigated, is also significantly affected in laryngeal cancer. While PIK3R1, HACE1, miR-139-3p, and miR-885-5p may act as tumor suppressor genes in the studied tumour type, miR-21-3p and miR-525-5p seem to have oncogenic properties. Our findings suggest that miR-885-5p and PIK3R1 are the best indicators for the classification of laryngeal cancer tissue and normal mucosa.

Fibroblast Growth Requires CT10 Regulator of Kinase (Crk) and Crk-like (CrkL)

CT10 regulator of kinase (Crk) and Crk-like (CrkL) are the cellular counterparts of the viral oncogene v-Crk Elevated levels of Crk and CrkL have been observed in many human cancers; inhibition of Crk and CrkL expression reduced the tumor-forming potential of cancer cell lines. Despite a close relationship between the Crk family proteins and tumorigenesis, how Crk and CrkL contribute to cell growth is unclear. We ablated endogenous Crk and CrkL from cultured fibroblasts carrying floxed alleles of Crk and CrkL by transfection with synthetic Cre mRNA (synCre). Loss of Crk and CrkL induced by synCre transfection blocked cell proliferation and caused shrinkage of the cytoplasm and the nucleus, formation of adherens junctions, and reduced cell motility. Ablation of Crk or CrkL alone conferred a much more modest reduction in cell proliferation. Reintroduction of CrkI, CrkII, or CrkL individually rescued cell proliferation in the absence of the endogenous Crk and CrkL, suggesting that Crk and CrkL play overlapping functions in regulating fibroblast growth. Serum and basic FGF induced phosphorylation of Akt, MAP kinases, and S6 kinase and Fos expression in the absence of Crk and CrkL, suggesting that cells lacking Crk and CrkL are capable of initiating major signal transduction pathways in response to extracellular stimuli. Furthermore, cell cycle and cell death analyses demonstrated that fibroblasts lacking Crk and CrkL become arrested at the G₁-S transition and undergo a modest apoptosis. Taken together, our results suggest that Crk and CrkL play essential overlapping roles in fibroblast growth.

Reciprocal regulation of Abl kinase by Crk Y251 and Abi1 controls invasive phenotypes in glioblastoma

Crk is the prototypical member of a class of Src homology 2 (SH2) and Src homology 3 (SH3) domain-containing adaptor proteins that positively regulate cell motility via the activation of Rac1 and, in certain tumor types such as GBM, can promote cell invasion and metastasis by mechanisms that are not well understood. Here we demonstrate that Crk, via its phosphorylation at Tyr251, promotes invasive behavior of tumor cells, is a prominent feature in GBM, and correlating with aggressive glioma grade IV staging and overall poor survival outcomes. At the molecular level, Tyr251 phosphorylation of Crk is negatively regulated by Abi1, which competes for Crk binding to Abl and attenuates Abl transactivation. Together, these results show that Crk and Abi1 have reciprocal biological effects and act as a molecular rheostat to control Abl activation and cell invasion. Finally, these data suggest that Crk Tyr251 phosphorylation regulate invasive cell phenotypes and may serve as a biomarker for aggressive GBM.

Antitumour actions of interferons: implications for cancer therapy

The interferons (IFNs) are a family of cytokines that protect against disease by direct effects on target cells and by activating immune responses. The production and actions of IFNs are finely tuned to achieve maximal protection and avoid the potential toxicity associated with excessive responses. IFNs are back in the spotlight owing to mounting evidence that is reshaping how we can exploit this pathway therapeutically. As IFNs can be produced by, and act on, both tumour cells and immune cells, understanding this reciprocal interaction will enable the development of improved single-agent or combination therapies that exploit IFN pathways and new 'omics'-based biomarkers to indicate responsive patients.

Cyclophilin A promotes cell migration via the Abl-Crk signaling pathway

Cyclophilin A (CypA) is overexpressed in a number of human cancer types, but the mechanisms by which the protein promotes oncogenic properties of cells are not understood. Here we demonstrate that CypA binds the CrkII adaptor protein and prevents it from switching to the inhibited state. CrkII influences cell motility and invasion by mediating signaling through its SH2 and SH3 domains. CrkII Tyr221 phosphorylation by the Abl or EGFR kinases induces an inhibited state of CrkII by means of an intramolecular SH2-pTyr221 interaction, causing signaling interruption. We show that the CrkII phosphorylation site constitutes a binding site for CypA. Recruitment of CypA sterically restricts the accessibility of Tyr221 to kinases, thereby suppressing CrkII phosphorylation and promoting the active state. Structural, biophysical and in vivo data show that CypA augments CrkII-mediated signaling. A strong stimulation of cell migration is observed in cancer cells wherein both CypA and CrkII are greatly upregulated.

The Role of Crk Adaptor Proteins in T-Cell Adhesion and Migration

Crk adaptor proteins are key players in signal transduction from a variety of cell surface receptors. They are involved in early steps of lymphocyte activation through their SH2-mediated transient interaction with signal transducing effector molecules, such as Cbl, ZAP-70, CasL, and STAT5. In addition, they constitutively associate, via their SH3 domain, with effector molecules, such as C3G, that mediate cell adhesion and regulate lymphocyte extravasation and recruitment to sites of inflammation. Recent studies demonstrated that the conformation and function of CrkII is subjected to a regulation by immunophilins, which also affect CrkII-dependent T-cell adhesion to fibronectin and migration toward chemokines. This article addresses mechanisms that regulate CrkII conformation and function, in general, and emphasizes the role of Crk proteins in receptor-coupled signaling pathways that control T-lymphocyte adhesion and migration to inflammatory sites.

Preclinical and clinical studies of the NEDD9 scaffold protein in cancer and other diseases

Cancer progression requires a significant reprogramming of cellular signaling to support the essential tumor-specific processes that include hyperproliferation, invasion (for solid tumors) and survival of metastatic colonies. NEDD9 (also known as CasL and HEF1) encodes a multi-domain scaffolding protein that assembles signaling complexes regulating multiple cellular processes relevant to cancer. These include responsiveness to signals emanating from the T and B cell receptors, integrins, chemokine receptors, and receptor tyrosine kinases, as well as cytoplasmic oncogenes such as BCR-ABL and FAK- and SRC-family kinases. Downstream, NEDD9 regulation of partners including CRKL, WAVE, PI3K/AKT, ERK, E-cadherin, Aurora-A (AURKA), HDAC6, and others allow NEDD9 to influence functions as pleiotropic as migration, invasion, survival, ciliary resorption, and mitosis. In this review, we summarize a growing body of preclinical and clinical data that indicate that while NEDD9 is itself non-oncogenic, changes in expression of NEDD9 (most commonly elevation of expression) are common features of tumors, and directly impact tumor aggressiveness, metastasis, and response to at least some targeted agents inhibiting NEDD9-interacting proteins. These data strongly support the relevance of further development of NEDD9 as a biomarker for therapeutic resistance. Finally, we briefly discuss emerging evidence supporting involvement of NEDD9 in additional pathological conditions, including stroke and polycystic kidney disease.

The role of CT10 regulation of kinase-like in cancer

ABSTRACT 

V-crk avian sarcoma virus CT10 oncogene homolog-like (CRKL) is a member of CRK family. It acts as an adaptor protein in intracellular signal transduction. CRKL has been reported overexpressed in a variety of cancers affecting the aggressive and malignant behaviors of cancer cells. CRKL seems to show a tumor-promotion role in gastric cancer, glioblastoma multiforme, hepatocellular carcinoma, bladder cancer, lung cancer, colon cancer, ovarian cancer, leukemia, breast cancer, head and neck cancer, rhabdomyosarcoma and neuroblastoma. The association of CRKL with malignant tumors and its potential action mechanisms were summarized. CRKL has the potential to be used as a biomarker for the diagnosis, treatment and prognosis of certain tumors.

Contribution of Crk adaptor proteins to host cell and bacteria interactions

The Crk adaptor family of proteins comprises the alternatively spliced CrkI and CrkII isoforms, as well as the paralog Crk-like (CrkL) protein, which is encoded by a different gene. Initially thought to be involved in signaling during apoptosis and cell adhesion, this ubiquitously expressed family of proteins is now known to play essential roles in integrating signals from a wide range of stimuli. In this review, we describe the structure and function of the different Crk proteins. We then focus on the emerging roles of Crk adaptors during Enterobacteriaceae pathogenesis, with special emphasis on the important human pathogens Salmonella, Shigella, Yersinia, and enteropathogenic Escherichia coli. Throughout, we remark on opportunities for future research into this intriguing family of proteins.

p130Cas scaffolds the signalosome to direct adaptor-effector cross talk during Kaposi's sarcoma-associated herpesvirus trafficking in human microvascular dermal endothelial cells

Kaposi's sarcoma-associated herpesvirus (KSHV) interacts with cell surface receptors, such as heparan sulfate, integrins (α3β1, αVβ3, and αVβ5), and EphrinA2 (EphA2), and activates focal adhesion kinase (FAK), Src, phosphoinositol 3-kinase (PI3-K), c-Cbl, and RhoA GTPase signal molecules early during lipid raft (LR)-dependent productive macropinocytic entry into human dermal microvascular endothelial cells. Our recent studies have identified CIB1 as a signal amplifier facilitating EphA2 phosphorylation and subsequent cytoskeletal cross talk during KSHV macropinocytosis. Although CIB1 lacks an enzymatic activity and traditional adaptor domain or known interacting sequence, it associated with the KSHV entry signal complex and the CIB1-KSHV association was sustained over 30 min postinfection. To identify factors scaffolding the EphA2-CIB1 signal axis, the role of major cellular scaffold protein p130Cas (Crk-associated substrate of Src) was investigated. Inhibitor and small interfering RNA (siRNA) studies demonstrated that KSHV induced p130Cas in an EphA2-, CIB1-, and Src-dependent manner. p130Cas and Crk were associated with KSHV, LRs, EphA2, and CIB1 early during infection. Live-cell microscopy and biochemical studies demonstrated that p130Cas knockdown did not affect KSHV entry but significantly reduced productive nuclear trafficking of viral DNA and routed KSHV to lysosomal degradation. p130Cas aided in scaffolding adaptor Crk to downstream guanine nucleotide exchange factor phospho-C3G possibly to coordinate GTPase signaling during KSHV trafficking. Collectively, these studies demonstrate that p130Cas acts as a bridging molecule between the KSHV-induced entry signal complex and the downstream trafficking signalosome in endothelial cells and suggest that simultaneous targeting of KSHV entry receptors with p130Cas would be an attractive potential avenue for therapeutic intervention in KSHV infection.

IMPORTANCE

Eukaryotic cell adaptor molecules, without any intrinsic enzymatic activity, are well known to allow a great diversity of specific and coordinated protein-protein interactions imparting signal amplification to different networks for physiological and pathological signaling. They are involved in integrating signals from growth factors, extracellular matrix molecules, bacterial pathogens, and apoptotic cells. The present study identifies human microvascular dermal endothelial (HMVEC-d) cellular scaffold protein p130Cas (Crk-associated substrate) as a platform to promote Kaposi's sarcoma-associated herpesvirus (KSHV) trafficking. Early during KSHV de novo infection, p130Cas associates with lipid rafts and scaffolds EphrinA2 (EphA2)-associated critical adaptor members to downstream effector molecules, promoting successful nuclear delivery of the KSHV genome. Hence, simultaneous targeting of the receptor EphA2 and scaffolding action of p130Cas can potentially uncouple the signal cross talk of the KSHV entry-associated upstream signal complex from the immediate downstream trafficking-associated signalosome, consequently routing KSHV toward lysosomal degradation and eventually blocking KSHV infection and associated malignancies.

Construction of an shRNA expression vector targeting the Crk gene: Potential role of Crk in liver fibrosis

AIM: To construct a short-hairpin RNA (shRNA) eukaryotic expression vector targeting the v-Crk avian sarcoma virus CT10 oncogene homolog gene (Crk) and to study the potential role of Crk in liver fibrosis.

METHODS: The shRNA oligonucleotide fragments were designed and synthesized based on the sequence of Crk mRNA. Double strands were then formed after annealing and inserted into the plko vector. Recombinant lentiviral vector was transfected into 293T cells to package lentivirus. LX-2 cells were then infected with the recombinant lentivirus and the function of Crk was studied after infection.

RESULTS: RT-PCR and Western bolt analyses indicated that after successful infection, both mRNA and protein expression was dramatically down-regulated, compared with the control group. Knockdown of Crk decreased the expression of collagen type 1 (Col1), α-smooth muscle actin (α-SMA) and the capacity of cell migration, but had no effect on cell proliferation.

CONCLUSION: We have successfully constructed an shRNA eukaryotic expression vector targeting the Crk gene. Knockdown of Crk can inhibit liver fibrosis possibly by suppressing the activation and migration of LX-2 cells.