Dissection of HEF1-dependent functions in motility and transcriptional regulation

A novel Cas family member, HEPL, regulates FAK and cell spreading

For over a decade, p130Cas/BCAR1, HEF1/NEDD9/Cas-L, and Efs/Sin have defined the Cas (Crk-associated substrate) scaffolding protein family. Cas proteins mediate integrin-dependent signals at focal adhesions, regulating cell invasion and survival; at least one family member, HEF1, regulates mitosis. We here report a previously undescribed novel branch of the Cas protein family, designated HEPL (for HEF1-Efs-p130Cas-like). The HEPL branch is evolutionarily conserved through jawed vertebrates, and HEPL is found in some species lacking other members of the Cas family. The human HEPL mRNA and protein are selectively expressed in specific primary tissues and cancer cell lines, and HEPL maintains Cas family function in localization to focal adhesions, as well as regulation of FAK activity, focal adhesion integrity, and cell spreading. It has recently been demonstrated that upregulation of HEF1 expression marks and induces metastasis, whereas high endogenous levels of p130Cas are associated with poor prognosis in breast cancer, emphasizing the clinical relevance of Cas proteins. Better understanding of the complete protein family should help inform prediction of cancer incidence and prognosis.

A new central scaffold for metastasis: parsing HEF1/Cas-L/NEDD9

Greater understanding of metastasis is required to improve cancer treatment outcomes. Recently, changes in expression of the scaffold protein HEF1/CAS-L/NEDD9 were found to be a potent prometastatic stimulus in melanoma and other cancers. Mechanistic studies suggest diverse cellular roles of HEF1 and highlight its importance in the response to extracellular cues that drive invasion and metastasis. As a metastatic "hub" for signaling in cancer, HEF1 may provide a useful target for drug discovery efforts.

Molecular basis for HEF1/NEDD9/Cas-L action as a multifunctional co-ordinator of invasion, apoptosis and cell cycle

Upregulation of the scaffolding protein HEF1, also known as NEDD9 and Cas-L, has recently been identified as a pro-metastatic stimulus in a number of different solid tumors, and has also been strongly associated with pathogenesis of BCR-Abl-dependent tumors. As the evidence mounts for HEF1/NEDD9/Cas-L as a key player in metastatic cancer, it is timely to review the molecular regulation of HEF1/NEDD9/Cas-L. Most of the mortality associated with cancer arises from uncontrolled metastases, thus a better understanding of the properties of proteins specifically associated with promotion of this process may yield insights that improve cancer diagnosis and treatment. In this review, we summarize the extensive literature regarding HEF1/NEDD9/Cas-L expression and function in signaling relevant to cell attachment, migration, invasion, cell cycle, apoptosis, and oncogenic signal transduction. The complex function of HEF1/NEDD9/Cas-L revealed by this analysis leads us to propose a model in which alleviation of cell cycle checkpoints and acquired resistance to apoptosis is permissive for a HEF1/NEDD9/Cas-L-promoted pro-metastatic phenotype.

New concepts regarding focal adhesion kinase promotion of cell migration and proliferation

Focal adhesion kinase (FAK) is a non-receptor cytoplasmic tyrosine kinase that plays a key role in the regulation of proliferation and migration of normal and tumor cells. FAK associates with integrin receptors and recruits other molecules to the site of this interaction thus forming a signaling complex that transmits signals from the extracellular matrix to the cell cytoskeleton. Crk-associated substrate (CAS) family members appear to play a pivotal role in FAK regulation of cell migration. Cellular Src bound to FAK phosphorylates CAS proteins leading to the recruitment of a Crk family adaptor molecule and activation of a small GTPase and c-Jun N-terminal kinase (JNK) promoting membrane protrusion and cell migration. The relocalization of CAS and signaling through specific CAS family members appears to determine the outcome of this pathway. FAK also plays an important role in regulating cell cycle progression through transcriptional control of the cyclin D1 promoter by the Ets B and Kruppel-like factor 8 (KLF8) transcription factors. FAK regulation of cell cycle progression in tumor cells requires Erk activity, cyclin D1 transcription, and the cyclin-dependent kinase (cdk) inhibitor p27Kip1. The ability of FAK to integrate integrin and growth factor signals resulting in synergistic promotion of cell migration and proliferation, and its potential regulation by nuclear factor kappa B (NFkappaB) and p53 and a ubiquitously expressed inhibitory protein, suggest that it is remarkable in its capacity to integrate multiple extracellular and intracellular stimuli.

Activation of the dioxin/aryl hydrocarbon receptor (AhR) modulates cell plasticity through a JNK-dependent mechanism

Environmental chemicals such as dioxin adversely affect immune, neurological and reproductive functions and have been implicated in cancer development. However, the mechanisms responsible for dioxin toxicity are still poorly understood. Here, we show that dioxin and related pollutants trigger a marked morphological change in epithelial cells that remodel their cytoskeleton to increase interaction with extra cellular matrix while loosening cell-cell contacts. Furthermore, dioxin-treated cells show increased motility. These dioxin-mediated effects are mimicked by constitutive expression and activation of the intracellular dioxin receptor (aryl hydrocarbon receptor (AhR)). They correlate with activation of the Jun NH2-terminal kinase (JNK) and are reverted by treatment with a JNK inhibitor. Dioxin-induced effects occur 48 h post-treatment initiation, a time scale, which argues for a genomic effect of the AhR, linked to induction of target genes. This novel Ahr action on cell plasticity points to a role in cancer progression.

Crk-associated substrate lymphocyte type regulates transforming growth factor-beta signaling by inhibiting Smad6 and Smad7

Crk-associated substrate lymphocyte type (Cas-L) is a 105 kDa docking protein with diverse functional properties, including regulation of cell division, proliferation, migration and adhesion. Cas-L is also involved in beta1 integrin- or antigen receptor-mediated signaling in B and T cells. In the present study, we demonstrate that Cas-L potentiates transforming growth factor-beta (TGF-beta) signaling pathway by interacting with Smad6 and Smad7. Immunoprecipitation experiments reveal that single domain deletion of full-length Cas-L completely abolishes its docking function with Smad6 and Smad7, suggesting that the natural structure of Cas-L is necessary for its association with Smad6 and Smad7. On the other hand, both N-terminal and C-terminal deletion mutants of Smad6 and Smad7 still retain their docking ability to Cas-L, suggesting that Smad6 and Smad7 possess several binding motifs to Cas-L. Moreover, Cas-L interaction with Mad-homology (MH)2 domain, but not with MH1 domain of Smad6 or Smad7, ameliorates TGF-beta-induced signaling pathway. Finally, depletion of Cas-L by small-interfering RNA oligo attenuates TGF-beta-induced growth inhibition of Huh-7 cells, with a concomitant reduction in phosphorylation of Smad2 and Smad3. These results strongly suggest that Cas-L is a potential regulator of TGF-beta signaling pathway.

Polarization and Movement of Keratocytes: A Multiscale Modelling Approach

Eukariotic cell motility is a complex phenomenon, in which the cytoskeleton and its major constituent, actin, play an essential role. Actin forms polymers of long, stiff filaments that are cross-linked into an anisotropic network inside a thin sheet-like cellular protrusion, the lamellipod. At the leading edge of this structure, polymerization of actin filaments creates the force that pushes out the membrane and leads to translocation of a motile cell. Dynamics of the actin network account for changes in cell shape, crawling motion and turning of the cell in response to external cues. Regulating the dynamics of the cytoskeleton, and playing a central role in signal transduction in the cell, are Cdc42, Rac and Rho (GTPases of the rho family, collectively known as the small G-proteins) and the actin nucleating complex, Arp2/3. In this paper, we use a multiscale modelling approach in a 2D model of a motile cell. We describe the mutual interactions of the small G-proteins, and their effects on capping and side-branching of actin filaments. We incorporate the pushing exerted by oriented actin filament ends on the cell edge, and a Rho-dependent contraction force. Combining these biochemical and mechanical aspects, we investigate the dynamics of a model epidermal fish keratocyte through in silico experiments. Our model gives insight into how, in response to some cue, a cell can polarize, form a leading edge, and move; concomitantly it explains how a keratocyte cell can maintain its shape and polarity, even after removal of the initial stimulus, and how it can change direction quickly in response to changes in its environment. We show that establishment of polarity stems from interactions of Cdc42, Rac and Rho, while maintenance and robustness of polarity is due to the rapid cytosolic diffusion of the inactive (GDI-bound) forms of the small G-proteins. Our model produces a cell shape that closely resembles the keratocytes and correct speeds for biologically reasonable parameter values. Movies of the simulations can be obtained from http://theory.bio.uu.nl/stan/keratocyte.

HEF1 is a necessary and specific downstream effector of FAK that promotes the migration of glioblastoma cells

The highly invasive behavior of glioblastoma cells contributes to the morbidity and mortality associated with these tumors. The integrin-mediated adhesion and migration of glioblastoma cells on brain matrix proteins is enhanced by stimulation with growth factors, including platelet-derived growth factor (PDGF). As focal adhesion kinase (FAK), a nonreceptor cytoplasmic tyrosine kinase, has been shown to promote cell migration in various other cell types, we analysed its role in glioblastoma cell migration. Forced overexpression of FAK in serum-starved glioblastoma cells plated on recombinant (rec)-osteopontin resulted in a twofold enhancement of basal migration and a ninefold enhancement of PDGF-BB-stimulated migration. Both expression of mutant FAK(397F) and the downregulation of FAK with small interfering (si) RNA inhibited basal and PDGF-stimulated migration. FAK overexpression and PDGF stimulation was found to increase the phosphorylation of the Crk-associated substrate (CAS) family member human enhancer of filamentation 1 (HEF1), but not p130CAS or Src-interacting protein (Sin)/Efs, although the levels of expression of these proteins was similar. Moreover downregulation of HEF1 with siRNA, but not p130CAS, inhibited basal and PDGF-stimulated migration. The phosphorylated HEF1 colocalized with vinculin and was associated almost exclusively with 0.1% Triton X-100 insoluble material, consistent with its signaling at focal adhesions. FAK overexpression promoted invasion through normal brain homogenate and siHEF1 inhibited this invasion. Results presented here suggest that HEF1 acts as a necessary and specific downstream effector of FAK in the invasive behavior of glioblastoma cells and may be an effective target for treatment of these tumors.

Deregulation of HEF1 impairs M-phase progression by disrupting the RhoA activation cycle

The focal adhesion-associated signaling protein HEF1 undergoes a striking relocalization to the spindle at mitosis, but a function for HEF1 in mitotic signaling has not been demonstrated. We here report that overexpression of HEF1 leads to failure of cells to progress through cytokinesis, whereas depletion of HEF1 by small interfering RNA (siRNA) leads to defects earlier in M phase before cleavage furrow formation. These defects can be explained mechanistically by our determination that HEF1 regulates the activation cycle of RhoA. Inactivation of RhoA has long been known to be required for cytokinesis, whereas it has recently been determined that activation of RhoA at the entry to M phase is required for cellular rounding. We find that increased HEF1 sustains RhoA activation, whereas depleted HEF1 by siRNA reduces RhoA activation. Furthermore, we demonstrate that chemical inhibition of RhoA is sufficient to reverse HEF1-dependent cellular arrest at cytokinesis. Finally, we demonstrate that HEF1 associates with the RhoA-GTP exchange factor ECT2, an orthologue of the Drosophila cytokinetic regulator Pebble, providing a direct means for HEF1 control of RhoA. We conclude that HEF1 is a novel component of the cell division control machinery and that HEF1 activity impacts division as well as cell attachment signaling events.

Cell adhesion regulates Ser/Thr phosphorylation and proteasomal degradation of HEF1

Human enhancer of filamentation 1 (HEF1), a multifunctional docking protein of the Cas family, participates in integrin and growth factor signaling pathways that regulate global cellular processes including growth, motility and apoptosis. HEF1 consists of two isoforms, p105 and p115, the larger molecular weight form resulting from Ser/Thr phosphorylation of p105HEF1. The molecular mechanisms that regulate the interconversion of the two HEF1 species as well as the function of HEF1 Ser/Thr phosphorylation are unknown. Our study reveals that cell adhesion and detachment regulate the interconversion of the two HEF1 isoforms. Experiments using various inhibitors of cytoskeletal organization indicated that disruption of actin microfilaments but not intermediate filaments or microtubules resulted in a complete conversion of p115HEF1 to p105HEF1. The conversion of p115HEF1 to p105HEF1 was prevented by inhibition of protein phosphatase 2A (PP2A), suggesting that cytoskeletal regulation of PP2A activity controlled the dephosphorylation of p115HEF1. Degradation of endogenous HEF1 was dependent on proteasomes with the p115 species of HEF1 being preferentially targeted for turnover. Dephosphorylation of HEF1 by suspending cells or disrupting actin filaments protected HEF1 from degradation. These results suggest that the adhesion-dependent actin organization regulates proteasomal turnover of HEF1 through the activity of PP2A.

The Cas family docking protein, HEF1, promotes the formation of neurite-like membrane extensions

The Cas family proteins are a family of adhesion docking molecules that mediate protein-protein interactions and contribute to a number of signal transduction pathways. Recent studies of two family members, p130Cas and Sin, have suggested that they may play a role in neurite formation. The current study demonstrates that the third family member, HEF1, can also stimulate the formation of neurite-like processes, in the presence of Rho kinase inhibitors. The HEF1-promoted processes actively extend from the cell body and resemble neurites both in the manner of process extension and in the distribution of adhesion-associated molecules. The HEF1-promoted processes are dependent on the presence of an intact microtubule system and can be inhibited by co-expression of either constitutively active Rac or Cdc42 GTPase. Together, our data support a role for the Cas proteins in regulating cellular morphologies that contribute to tissue specialization.

The focal adhesion scaffolding protein HEF1 regulates activation of the Aurora-A and Nek2 kinases at the centrosome

Although HEF1 has a well-defined role in integrin-dependent attachment signalling at focal adhesions, it relocalizes to the spindle asters at mitosis. We report here that overexpression of HEF1 causes an increase in centrosome numbers and multipolar spindles, resembling defects induced by manipulation of the mitotic regulatory kinase Aurora-A (AurA). We show that HEF1 associates with and controls activation of AurA. We also show that HEF1 depletion causes centrosomal splitting, mono-astral spindles and hyperactivation of Nek2, implying additional action earlier in the cell cycle. These results provide new insight into the role of an adhesion protein in coordination of cell attachment and division.

Crk-associated substrate (Cas) family member, NEDD9, is regulated in human neuroblastoma cells and in the embryonic hindbrain by all-trans retinoic acid

The vitamin A metabolite, all-trans retinoic acid (atRA), plays an essential role in vertebrate embryogenesis, including development of the nervous system. In the human neuroblastoma cell line, SH-SY5Y, atRA rapidly induces (within 4 hr) the expression of the Crk-associated substrate (Cas) family member, neural precursor cell-expressed, developmentally down-regulated gene 9 (NEDD9) also called the human enhancer of filamentation (HEF1). NEDD9 is expressed in the developing hindbrain (5-somite stage) in the presumptive rhombomeres 2, 3, and 5 before the onset of overt segmentation. Exposure of rat embryos to excess atRA at times ranging from E9.25 to E12 leads to altered NEDD9 expression in the developing hindbrain within 6 hr. NEDD9 expression is also perturbed in vitamin A-deficient embryos. A putative retinoic acid response element in the 5' region of the NEDD9 promoter binds specifically to a RXR/RAR heterodimer and forms a higher molecular weight complex upon addition of a retinoic acid receptor-specific antibody. Regulation of NEDD9 may be an important means whereby atRA promotes cell spreading and neurite outgrowth in SH-SY5Y human neuroblastoma cells, and NEDD9 represents a new downstream target of atRA and its receptors in the developing hindbrain.

All-trans retinoic acid-responsive genes identified in the human SH-SY5Y neuroblastoma cell line and their regulated expression in the nervous system of early embryos

The vitamin A metabolite, all-trans retinoic acid (atRA), is required for embryonic development. atRA binds to the nuclear retinoic acid receptors and regulates the transcription of specific target genes. In order to identify atRA-induced genes that play a role in neural development, a subtractive library was created from SH-SY5Y neuroblastoma cells, a human cell line that exhibits changes in cell adhesion and neurite outgrowth after exposure to the vitamin A acid. We report here the identification of 14 genes that are rapidly induced by atRA (retinoic acid induced in neuroblastoma or RAINB), eight of which were previously not known to be atRA responsive (BTBD11, calmin, cyclin M2, ephrin B2, HOXD10, NEDD9, RAINB6 and tenascin R). mRNA regulation by atRA was confirmed in SH-SY5Y cells by Northern blotting, and gene regulation was studied in additional human cell lines using the quantitative polymerase chain reaction. The majority of the atRA-responsive clones revealed in this screen are highly expressed in the nervous system of developing rat embryos. Further, the expression of several of these genes is perturbed in developing rat embryos exposed to excess atRA or conversely, deprived of sufficient retinoid during early development. We propose that a subset of these genes lie downstream of atRA and its receptors in the regulation of neurite outgrowth and cell adhesion in both neural and non-neural tissues within the developing embryo.

Whole genome expression profiling of advance stage papillary serous ovarian cancer reveals activated pathways

Ovarian cancer is the most lethal type of gynecologic cancer in the Western world. The high case fatality rate is due in part because most ovarian cancer patients present with advanced stage disease which is essentially incurable. In order to obtain a whole genome assessment of aberrant gene expression in advanced ovarian cancer, we used oligonucleotide microarrays comprising over 40,000 features to profile 37 advanced stage papillary serous primary carcinomas. We identified 1191 genes that were significantly (P < 0.001) differentially regulated between the ovarian cancer specimens and normal ovarian surface epithelium. The microarray data were validated using real time RT-PCR on 14 randomly selected differentially regulated genes. The list of differentially expressed genes includes ones that are involved in cell growth, differentiation, adhesion, apoptosis and migration. In addition, numerous genes whose function remains to be elucidated were also identified. The microarray data were imported into PathwayAssist software to identify signaling pathways involved in ovarian cancer tumorigenesis. Based on our expression results, a signaling pathway associated with tumor cell migration, spread and invasion was identified as being activated in advanced ovarian cancer. The data generated in this study represent a comprehensive list of genes aberrantly expressed in serous papillary ovarian adenocarcinoma and may be useful for the identification of potentially new and novel markers and therapeutic targets for ovarian cancer.

Keratocyte-like locomotion inamiB-nullDictyosteliumcells

Starved Dictyostelium amoebae continuously change their shape and they are elongated along the front-rear axis during locomotion. In contrast, we found that disruption of the amiB gene, which had been identified as a gene required for the aggregation process during development, caused these cells to move in a manner similar to fish keratocytes. Starved amiB- cells were elongated laterally and had one large lamellipodium along the front side arc of the cell. These cells moved unidirectionally for long distances maintaining the half-moon shape, and this movement followed the predictions of the graded radial extension model, which was originally developed to describe the keratocyte movements. Furthermore, the distributions of actin, Arp2, and myosin II in amiB- cells were similar to those in keratocytes. Therefore, locomotion by keratocytes and amiB- cells appears to be driven by similar mechanisms of cytoskeletal regulation. Double knockout cells lacking both AmiB and myosin II were still able to move unidirectionally in a keratocyte-like manner, although the frequency of those movements was lower. Thus, myosin II is dispensable for the unidirectional movement, though it likely functions in the maintenance of the characteristic half-moon shape. This mutant cell can be a useful tool for further molecular genetic analysis of the mechanism of cell locomotion.

Atrophin-1-interacting Protein 4/Human Itch Is a Ubiquitin E3 Ligase for Human Enhancer of Filamentation 1 in Transforming Growth Factor-β Signaling Pathways

Atrophin-1-interacting protein 4 (AIP4) is the human homolog of the mouse Itch protein (hItch), an E3 ligase for Notch and JunB. Human enhancer of filamentation 1 (HEF1) has been implicated in signaling pathways such as those mediated by integrin, T cell receptor, and B cell receptor and functions as a multidomain docking protein. Recent studies suggest that HEF1 is also involved in the transforming growth factor-beta (TGF-beta) signaling pathways, by interacting with Smad3, a key signal transducer downstream of the TGF-beta type I receptor. The interaction of Smad3 with HEF1 induces HEF1 proteasomal degradation, which was further enhanced by TGF-beta stimulation. The detailed molecular mechanisms of HEF1 degradation regulated by Smad3 were poorly understood. Here we report our studies that demonstrate the function of AIP4 as an ubiquitin E3 ligase for HEF1. AIP4 forms a complex with both Smad3 and HEF1 through its WW domains in a TGF-beta-independent manner and regulates HEF1 ubiquitination and degradation, which can be enhanced by TGF-beta stimulation. These findings reveal a new mechanism for Smad3-regulated proteasomal degradation events and also broaden the network of cross-talk between the TGF-beta signaling pathway and those involving HEF1 and AIP4.

Human enhancer of invasion-cluster, a coiled-coil protein required for passage through mitosis

In a cross-species overexpression approach, we used the pseudohyphal transition of Saccharomyces cerevisiae as a model screening system to identify human genes that regulate cell morphology and the cell cycle. Human enhancer of invasion-cluster (HEI-C), encoding a novel evolutionarily conserved coiled-coil protein, was isolated in a screen for human genes that induce agar invasion in S. cerevisiae. In human cells, HEI-C is primarily localized to the spindle during mitosis. Depletion of HEI-C in vivo with short interfering RNAs results in severe mitotic defects. Analysis by immunofluorescence, flow cytometry analysis, and videomicroscopy indicates that HEI-C-depleted cells form metaphase plates with normal timing after G(2)/M transition, although in many cases cells have disorganized mitotic spindles. Subsequently, severe defects occur at the metaphase-anaphase transition, characterized by a significant delay at this stage or, more commonly, cellular disintegration accompanied by the display of classic biochemical markers of apoptosis. These mitotic defects occur in spite of the fact that HEI-C-depleted cells retain functional cell cycle checkpoints, as these cells arrest normally following nocodazole or hydroxyurea treatment. These results place HEI-C as a novel regulator of spindle function and integrity during the metaphase-anaphase transition.

A novel RING finger protein, human enhancer of invasion 10, alters mitotic progression through regulation of cyclin B levels

The process of cellular morphogenesis is highly conserved in eukaryotes and is dependent upon the function of proteins that are centrally involved in specification of the cell cycle. The human enhancer of invasion clone 10 (HEI10) protein was identified from a HeLa cell library based on its ability to promote yeast agar invasion and filamentation. Through two-hybrid screening, the mitotic cyclin B1 and an E2 ubiquitin-conjugating enzyme were isolated as HEI10-interacting proteins. Mutation of the HEI10 divergent RING finger motif (characteristic of E3 ubiquitin ligases) and Cdc2/cyclin binding and phosphorylation sites alter HEI10-dependent yeast phenotypes, including delay in G(2)/M transition. In vertebrates, the addition of HEI10 inhibits nuclear envelope breakdown and mitotic entry in Xenopus egg extracts. Mechanistically, HEI10 expression reduces cyclin B levels in cycling Xenopus eggs and reduces levels of the cyclin B ortholog Clb2p in yeast. HEI10 is itself a specific in vitro substrate of purified cyclin B/cdc2, with a TPVR motif as primary phosphorylation site. Finally, HEI10 is itself ubiquitinated in egg extracts and is also autoubiquitinated in vitro. These and other points lead to a model in which HEI10 defines a divergent class of E3 ubiquitin ligase, functioning in progression through G(2)/M.

Regulation of HEF1 expression and phosphorylation by TGF-beta 1 and cell adhesion

Transforming growth factor-beta1 (TGF-beta1) is a multipotential cytokine, which regulates remodeling of tissue extracellular matrix during early tumorigenesis and wound healing. Human enhancer of filamentation-1 (HEF1), a multifunctional docking protein, is involved in integrin-based signaling, which affects cell motility, growth, and apoptosis. Our studies reveal that TGF-beta1 is a potent inducer of HEF1 gene transcription in human dermal fibroblasts. TGF-beta1 promoted HEF1 expression in a dose-dependent manner and resulted in a 16-fold increase in HEF1 protein level. TGF-beta1 had no effect on the stability of either HEF1 protein or mRNA. The TGF-beta1-induced HEF1 expression was independent of cell adhesion and resistant to cytoskeleton disruption. TGF-beta1 increased levels of both p105 and p115 HEF1 in adherent fibroblasts. Digestion with specific phosphatases indicated that the p115HEF1 resulted from serine/threonine phosphorylation of p105HEF1. The appearance of the p115HEF1 as well as tyrosine phosphorylation of p105HEF1 required cell adhesion and/or an organized cytoskeleton. An in vitro kinase assay indicated that p105HEF1 was a substrate for Src. PP1, a specific Src kinase inhibitor, was able to block adhesion-dependent tyrosine phosphorylation of p105HEF1. These findings suggest that TGF-beta1 regulates HEF1 gene expression and that HEF1 phosphorylation is dependent on cell adhesion and Src kinase activity.

Analysis of gene expression profile in p130(Cas)-deficient fibroblasts

p130(Cas) (Cas) is a docking protein that becomes tyrosine phosphorylated in v-Src- or v-Crk-transformed cells and in integrin-stimulated cells. Cas -/- fibroblasts show defects in stress fiber formation, cell spreading, cell migration, and transformation by activated Src. To further characterize the role of Cas in signaling, we compared the expression profile in Cas -/- fibroblasts with that in Cas-re-expressing fibroblasts using the microarray methods. In Cas -/- fibroblasts, the expression of heme oxygenase 1 and caveolin-1 was reduced, but the expression of procollagen 1 alpha 1, procollagen 3 alpha 1, procollagen 11 alpha 1, elastin, periostin, TSC-36, and MARCKS was enhanced. The domains in Cas necessary for the change varied among these genes. Activated Src reduced the expression of most of these genes both in Cas -/- and in Cas +/+ fibroblasts. These results suggest the existence of signaling pathways that emanate from Cas to gene expression.