Les cellules dendritiques sont des cellules du système immunitaire inné qui jouent un rôle important dans la reconnaissance immunitaire contre les agents pathogènes étrangers. Elles peuvent également prévenir les maladies auto-immunes à l'état basal. En raison de l'importance des cellules dendritiques dans la régulation immunitaire, il est important de comprendre comment le développement, l'état d'homéostasie et de quiescence des ces cellules sont contrôlées dans des conditions physiologiques et pathologiques. Cette étude permettra non seulement de mieux comprendre le contrôle de la régulation immunitaire, mais aussi de contribuer au développement de nouvelles approches pour traiter les maladies infectieuses et auto-immunes, ainsi que les cancers. Notre laboratoire a montré que C-CBL et CBL-B, deux membres de la famille CBL des ubiquitine ligases E3, jouent un rôle redondant dans la régulation négative du développement et de l'activation des cellules T et B. En l'absence de CBL dans les cellules T ou B, les souris développent des maladies auto-immunes sévères, indiquant que C-CBL et CBL-B jouent un rôle dans le système auto-immun. Partant de ces observations, nous proposons que CBL-B et C-CBL peuvent également jouer un rôle similaire dans le développement et la fonction des cellules dendritiques. Pour étudier cette possibilité, nous avons généré une souris knockout de Cbl spécifiques aux cellules dendritiques (dKO). Nous avons trouvé que cette mutation provoque une modification de l'homéostasie d'un sous-ensemble des cellules dendritiques (DC), y compris une augmentation marquée des CD8a+ cDCs et une réduction des pDC dans la rate. Cette modification est causée par la prolifération accrue des CD8a+ cDCs. Dans les CD8a+ cDCs mutantes, les voies de signalisation PKB et ERK sont constitutivement activées. Blocage de la signalisation de MTOR par la rapamycine atténue de manière significative l'hyperprolifération des CD8a+ cDCs in vitro et in vivo, indiquant que l'hyperactivation de MTOR est en partie responsable de l'augmentation CD8a+ cDCs. Les protéines CBL contrôlent l'ubiquitination et la dégradation du récepteur FLT3, suggérant que les protéines CBL contrôlent ainsi l'homéostasie de CD8a+ cDCs. Outre ces effets sur le développement des cellules dendritiques, nous avons trouvé que les souris Cbl dKO développent des inflammations sévères du foie et d'autres organes, caractérisées par une infiltration massive de leucocytes et une activation importante des cellules lymphocytes T périphériques. Les souris mutantes produisent des niveaux élevés de cytokines inflammatoires et de chimiokines, telles que le TNF-α, l'IL-6 et le CCL2. Les souris mutantes développent une maladie inflammatoire du foie. L'ensemble de ces observations montrent que les protéines CBL jouent un rôle essentiel dans le maintien de la quiescence immunitaire chez la souris. Puisque les souris dKO Cbl développent principalement une inflammation sévère du foie, il serait intéressant d'étudier si les voies contrôlées par les protéines CBL contribuent également au développement d'une inflammation du foie chez l'homme. / Dendritic cells (DCs) are innate immune cells that play an important role in immune recognition against foreign pathogens. They may also sense self-cues and prevent autoimmune diseases under the steady-state. Given the importance of DCs in immune regulation, it is conceivable that understanding how DCs development, homeostasis and functional quiescence are regulated under physiological and pathological conditions will not only bring insight into our knowledge how immune regulation is controlled but also some new approaches to treat infectious and autoimmune diseases and even cancers. Dr. Gu’s lab previously has shown that C-CBL and CBL-B, two members of the CBL family of E3 ubiquitin ligases, play a redundant negative regulatory role in both T cells and B cells development and activation. In the absence of CBL family of proteins in either T or B cells, mice develop severe autoimmune diseases, indicating that C-CBL and CBL-B restrain immune system against self. Based on these discoveries, we propose that C-CBL and CBL-B may also have a similar regulatory role in DC development and function. To study this possibility, we have generated DC-specific Cbl dKO mice. We have found that the Cbl dKO mutation results in an altered homeostasis of DC subsets, including a marked increase of CD8a+ cDCs and reduction of pDCs in the spleen (SP). This alteration is due to the enhanced proliferation of CD8a+ cDCs rather than the preferential lineage commitment to CD8a+ cDCs. In the mutant CD8a+ cDCs, both the PKB signaling pathway and ERK signaling pathways are constitutively activated. Blockage of MTOR signaling by Rapamycin significantly attenuates the hyperproliferation of CD8a+ cDCs both in vitro and in vivo, indicating that hyperactivation of MTOR is at least one of the reasons leading to CD8a+ cDC expansion. CBL proteins regulate ubiquitination and degradation of FLT3. Based on these results, we conclude that CBL proteins control CD8a+ cDC homeostasis through promoting FLT3 ubiquitination and degradation. In addition to the altered DC development, we have found that Cbl dKO mice develop severe liver and other organ inflammation characterized by massive leukocytes infiltration and profound peripheral T cell activation. Mutant mice produce high levels of inflammatory cytokines and chemokines including TNF-a, IL-6, CCL2, etc. Most strikingly, the mutant mice develop a similar liver inflammatory disease even in the absence of T and B cells. These findings together indicate that CBL proteins play an essential role in the maintenance of immune quiescence in mice. Since Cbl dKO mice mainly develop severe liver inflammation, it will be interesting to study whether the pathways controlled by CBL proteins also contribute to the development of liver inflammation in humans.

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Le travail présenté a porté sur l’analyse in vivo du proto-oncogène c-cbl, dont la forme connue est c-Cbl (p120cbl). Il s’agit d’une E3-Ubiquitine ligase et un poly-adaptateur moléculaire. Nous avons montré l’androgéno-dépendance de l’expression de c-Cbl dans les cellules germinales testiculaires et les cellules épithéliales de la prostate de rats et de souris. Nous avons montré la régulation anti-apoptotique exercée in vivo par la c-Cbl dans la prostate par comparaison des souris c-cbl invalidées ou non pour c-cbl (KO ou WT). L’effet exercé par c-cbl dans le testicule est pro-apoptotique (J.Cell Biol, 2005), que nous avons ultérieurement attribué à une nouvelle isoforme testiculaire de c-Cbl (Δ-c-Cbl). La comparaison des MEF KO et WT après induction d’apoptose par l’étoposide, a conforté l’effet anti-apoptotique exercée in vivo par c-Cbl dans la prostate. Elle a aussi montré la forte apoptose des MEF KO au peroxyde d’hydrogène : c-Cbl peut être considérée comme un protecteur du stress oxydant. L’intensité du stress oxydant associé aux cancers et leur forte résistance à l’apoptose sont des propriétés qui pourraient être reliées à c-Cbl. L’analyse in situ effectuée à partir de tumeurs congelées et de Tissue Microarrays (TMA) a montré une expression élevée de c-Cbl dans certains cancers, dont l’intensité pourrait correspondre à la gravité de l’atteinte anatomo-pathologique. La protéine c-Cbl est apparue être un marqueur d’agressivité du cancer de la prostate, probablement de l’ovaire, de l’utérus, du cerveau, du poumon, du colon et du rectum. Nous la considérons aussi comme une cible thérapeutique car, protecteur du stress oxydant, elle prendrait part à la résistance à l’apoptose des cellules tumorales. Un brevet a été déposé (2009, co-inventeurs : S.Yakoub et al). Un article rapportant ces résultats est en cours de soumission (S. Yakoub et al) / This work has focused on the in vivo analysis of the proto-oncogene c-cbl, coding for c-Cbl (p120cbl). We demonstrated the androgen-dependency of c-Cbl in the testicular germ cells and the prostatic epithelial cells of rats and mice. We then identified the anti-apoptotic regulation exerted by p120cbl in the prostate, comparing mouse c-cbl KO and WT, unlike this exerted in the testis (J.Cell Biol, 2005). We reported this difference to the high expression in testis of a new c-Cbl isoform, Δc-Cbl. The comparison of MEF KO and WT allowed confirming the anti-apoptotic regulation to etoposide exerted by c-Cbl. A very high apoptotic effect was observed in MEF KO with H2O2: c-Cbl is a strong stress oxidative protector. Knowing the intensity of oxidative stress in several cancers and their particular resistance to apoptosis as well, the in situ analysis of these malignancies was made from frozen tumours and tissue microassays (TMA). c-Cbl was indeed highly expressed and its intensity appears to reflect the aggressiveness of the pathology. c-Cbl could then be considered as a marker of severity of prostate cancer but probably also ovary, uterus, brain, lung, colon and rectum. It can also be considered as a therapeutic target involved in resistance to apoptosis as a stress oxidative protector. A patent was filed in the United States (2009, co-inventors: S. Yakoub et al)

Das Dorsalgefäß von Drosophila ist ein wertvolles Modellsystem für die Untersuchung der genetischen und molekularen Mechanismen der Kardiogenese. Ein Schlüsselereignis der Kardiogenese ist die Bildung eines Herzlumens, durch das die Hämolymphe gepumpt wird, um Nährstoffe und Zellen des angeborenen Immunsystems zu zirkulieren. Ein Schwerpunkt meiner Arbeit umfasste die Identifizierung neuer Gene, die im embryonalen Dorsalgefäß von Drosophila exprimiert sind. Dafür habe ich die Expression von 101 Genen, deren Orthologe spezifisch im Herzen von Zebrafisch exprimiert sind, in Drosophila untersucht. Ich identifizierte ein Gen, das für das Cbl-assoziierte Protein (CAP) kodiert. Durch Herstellung eines anti-CAP Antikörpers konnte ich erstmals eine detaillierte Lokalisation des CAP-Proteins im Dorsalgefäß beschreiben. Interessanterweise stellte sich dabei heraus, dass CAP ähnlich wie die homologen Vertebraten Proteine embryonal an den fokalen Adhäsionskontakten der Kardioblasten und im adulten Dorsalgefäß auch an den Z-Scheiben und den Zell-Zell-Kontaktstellen der Kardiomyozyten lokalisiert ist. Des Weiteren untersuchte ich, welche Auswirkungen der Verlust der CAP Funktion auf die Herzentwicklung hat. Für die Analyse der CAP-Mutanten nutzte ich neben Immunhistochemischen Methoden auch ultrastrukturelle Analysen mittels TEM-Mikroskopie. So konnte ich zeigen, dass embryonale Dorsalgefäße von CAP-Mutanten eine fehlerhafte Anzahl sowie Anordnung der Kardioblasten und Lumendefekte aufweisen. Ein genetischer Interaktionstest untermauerte meine Vermutung, dass CAP mit dem Integrinsignalweg während der embryonalen Dorsalgefäßentwicklung interagiert. Live-Aufnahmen des pumpenden Dorsalgefäßes von Drosophila L3-Larven und Injektionstests an späten Puppen zeigten zudem, dass der Verlust der CAP Funktion auch zu starken Defekten in der Funktionalität des larvalen und adulten Dorsalgefäßes führt. / The heart of Drosophila provides a valuable model system for the examination of the genetic and molecular mechanisms that guide cardiogenesis. A key event of cardiogenesis is the formation of a heart lumen through which the hemolymph is pumped to circulate nutrients and cells of the innate immune system. A main focus of my work was the identification of new genes that are expressed in the embryonic heart of Drosophila. Therefore I studied the expression of 101 genes, whose orthologues are expressed specifically in the heart of zebrafish. I identified a gene that encodes for the Cbl-associated protein (CAP). By generating an anti-CAP antibody I could describe the localization of the CAP protein in the heart for the first time in detail. Interestingly, it turned out that CAP is located similar to the homologous vertebrate proteins at the focal adhesion contacts of cardioblasts in the embryo and at the Z-discs and the cell-cell contact sites of cardiomyocytes in the adult heart. I also examined the consequences of the loss of CAP function on heart development. For the analysis of the CAP mutants I used immunohistochemical and ultrastructural analysis by TEM microscopy. So I was able to demonstrate that embryonic hearts of CAP mutants show a defective number and arrangement of cardioblasts and lumen defects. A genetic interaction test substantiated my guess that CAP interacts with the Integrin signaling pathway during embryonic heart development. Live recordings of the pumping heart of Drosophila L3 larvae and injection tests of late pupae also showed that the loss of CAP function leads to severe defects in the functionality of the larval and adult heart.

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Orientadores: Marcelo Menossi Teixeira, Ricardo Aparicio / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-16T01:59:50Z (GMT). No. of bitstreams: 1 Fonseca_JosePedro_D.pdf: 3971415 bytes, checksum: b23d47eff6b16f53235b5d581fcd3ae6 (MD5) Previous issue date: 2010 / Resumo: Estresses bióticos e abióticos como a seca, salinidade e ataque por patógenos são responsáveis por perdas significantes em culturas de grãos ao redor do mundo. Diversos genes são regulados em resposta a esses fatores e podem ser ativados ou reprimidos para gerar uma resposta específica na planta de maneira a gerar uma resposta de defesa que atenue os efeitos do estresse e promoção de tolerância pela planta. É importante entendermos o funcionamento desses mecanismos moleculares, e dos genes e proteínas envolvidas nestas vias de sinalização para um melhor conhecimento de como estas vias de transdução operam em plantas, bem como no desenvolvimento de variedades de plantas tolerantes. No capítulo I deste trabalho nós descrevemos a análise funcional de um motivo de ligação do fator TGA localizado na região promotora do gene NIMIN-1 que é altamente induzido por ácido salicílico (SA) durante defesa de plantas (estresse biótico). Fatores TGA desempenham um papel chave na defesa de plantas através da interação com elementos presentes na região promotora de genes de defesa para induzir a sua expressão. O ácido salicílico (SA) é um fito-hormônio que induz a expressão do gene que codifica a proteína NIMIN-1. Essa proteína interage com a proteína NPR1/NIM1, reguladora da resistência sistêmica adquirida (SAR). Neste trabalho foi investigado se um motivo de ligação do fator TGA2 "TGACG", localizado na região promotora imediatamente anterior ao sítio de iniciação da transcrição de NIMIN-1, é necessário a indução de NIMIN-1 por ácido salicílico. Uma versão mutagenizada do promotor do gene NIMIN-1 foi gerada por mutação sítio-dirigida. Nós geramos construções T-DNA nas quais tanto a região promotora nativa quanto a mutagenizada foram fusionadas aos repórteres proteína verde fluorescente (GFP) e beta-glucuronidase (GUS). Foram geradas plantas transgênicas e a expressão de GFP sob o controle da região promotora de NIMIN-1 foi observada em raízes, no pecíolo e folhas de Arabidopsis. A atividade dirigida pelo promotor mutagenizado e o selvagem foi quantificada por PCR quantitativo em tempo real. Tanto a construção contendo o promotor de NIMIN-1 como a cópia endógena de NIMIN-1 foram induzidas por SA. Em contraste, a construção promotora mutagenizada foi bem menos sensível a SA que o promotor nativo de NIMIN-1. Esse dado indica que o motivo de ligação do fator TGA2 analisado está diretamente envolvido na modulação da expressão de NIMIN-1 induzida por SA em Arabidopsis. No capítulo II nós descrevemos a caracterização da proteína ScCBL1 de cana-de-çúcar que apresenta elevada identidade com membros da família de proteínas sensoras de cálcio do tipo calcineurina B (CBL) em plantas. Experimentos de duplo-híbrido realizados em nosso grupo mostram que a proteína ScCBL1 interage com uma proteína quinase (ScCIPK8). Trabalhos prévios também desenvolvidos em nosso laboratório demonstraram que ScCIPK8 está envolvida no metabolismo do carboidrato e é diferencialmente expressa em resposta a ABA. O gene ScCBL1 foi clonado e a proteína codificada expressa e purificada a partir do extrato solúvel por cromatografia de afinidade usando resina Ni-NTA e a proteína eluída foi usada para estudos estruturais. Análises por espectrometria por dicroísmo circular (CD) mostraram que a proteína ScCBL1 é composta predominantemente por ?-hélices, em concordância com programas de predição da sequência de aminoácido desta proteína. Experimentos de espalhamento de raio-x a baixos ângulos (SAXS) indicaram que as amostras obtidas da ScCBL1 estavam homogêneas e monodispersas em solução e que ocorre uma mudança em seu estado oligomérico quando adicionado o agente redutor DTT, ocorrendo uma diminuição na intensidade de espalhamento (I(0)) a uma ordem de 1,56 para a mesma concentração, acompanhado de uma diminuição de 10 Å em seu raio de giro. As analises por SAXS indicaram que a proteína ScCBL1 é pentamérica em seu estado nativo e um trímero quando adicionado DTT. Análises por SAXS também indicaram que a proteína ScCBL1 está enovelada em solução, apresentando estrutura terciária estável. A modelagem de baixa resolução ab initio, juntamente com a função de distribuição das distâncias P(r) indicaram que a proteína possui um formato alongado (prolato). Ensaios iniciais de cristalização a partir de amostras monodispersas da proteína ScCBL1, confirmadas por DLS, foram feitas e um monocristal simétrico de aproximadamente 0.05 mm de diâmetro obtido além de outros sinais promissores para um refinamento das condições de cristalização de ScCBL1 para determinação de sua estrutura tridimensional a uma alta resolução. Esses dados contribuem para uma caracterização inicial da estrutura da proteína ScCBL1 / Abstract: Many biotic and abiotic stresses such as drought, salinity and pathogen attack are responsible for major crop losses around the world. Several genes are regulated in response to these factors to counteract the stress effects and promote plant tolerance. Understanding the molecular mechanisms as well as the roles of genes and proteins involved in stress signaling pathways is key to a better understanding of plant tolerance. We report in chapter I the functional analysis of a TGA biding factor located in the promoter region of NIMIN-1 that is highly induced by SA during plant defense against pathogen attack (biotic stress). TGA factors play a key role in plant defense by binding to the promoter region of defense genes, inducing their expression. Salicylic acid (SA) induces the expression of the gene encoding NIMIN-1, which interacts with NPR1/NIM1, a key regulator of systemic acquired resistance. In this work we investigated whether the TGA2-binding motif TGACG located upstream of the NIMIN-1 gene is necessary for SA induction of NIMIN-1 expression. A mutated version of the NIMIN-1 promoter was created by site-directed mutagenesis. We generated T-DNA constructs in which native NIMIN-1 and mutated promoters were fused to green fluorescent protein and ?-glucuronidase reporters. We produced transgenic Arabidopsis plants and observed NIMIN-1 promoter-driven green fluorescent protein expression in the roots, petiole and leaves. Constructs were also agroinfiltrated into the leaves to evaluate gene expression of mutagenized and native promoters driving expression of GUS using quantitative real-time RT-PCR. We characterized the normal gene response to SA and compared it to the response of the mutant version of the NIMIN-1 promoter. Both the native NIMIN-1 construct and an endogenous copy of NIMIN-1 were induced by SA. However, the mutated promoter construct was much less sensitive to SA than the native NIMIN-1 promoter, indicating that this TGA2-binding motif is directly involved in the modulation of SA-induced NIMIN-1 expression in Arabidopsis. In chapter II we describe the characterization of a sugarcane ScCBL1 protein which displays high sequence identity to the calcium binding protein family calcineurin B-like (CBL) from plants. Using the two-hybrid system our group has shown that ScCBL1 binds to a protein kinase (ScCIPK8). Previous work done in our laboratory also showed that ScCIPK8 is involved in carbohydrate metabolism and that it is differentially expressed in response to ABA. ScCBL1 was cloned, expressed and purified by one round of affinity chromatography using a Ni-NTA resin and the purified eluted protein was used for structural analysis. Spectroscopic analysis by circular dichroism (CD) showed that ScCBL1 is mainly composed of ?-helices agreeing with secondary structure prediction by PredictProtein server. Small Angle X-Ray Scattering (SAXS) analysis showed that ScCBL1 sample is homogeneous and monodisperse in solution and that the protein undergoes an oligomeric change when DTT is added, with a decrease in scattering intensity (I(0)) by a factor of 1,56 for samples with the same concentration, together with a decrease in the radius of gyration of 10 Å. SAXS experiments also showed that ScCBL1 is pentameric in its native state and the protein undergoes a change in its oligomeric state to a trimer when DTT is added. SAXS experiments also showed the protein is folded in solution and ab initio modeling of ScCBL1 protein envelope together with the pair-distribution function P(r) indicates that the protein has a rod-like, elongated shape. An initial crystallization screening with ScCBL1 monodisperse samples (confirmed by DLS experiments) was carried out and some crystallization signals were obtained, including a single crystal of around 0.05 mm in length. These data shed light on the structural features of ScCBL1 / Doutorado / Genetica Vegetal e Melhoramento / Doutor em Genetica e Biologia Molecular

CBL proteins are E3 ubiquitin ligases and adaptor proteins. The mammalian homologs – CBL, CBL-B and CBL-3 show broad tissue expression; accordingly, the CBL proteins play roles in multiple cell types. We have investigated the function of the CBL-B protein in hematopoietic cells and fibroblasts. The causative agent of chronic myeloid leukemia (CML) is BCR-ABL. This oncogenic fusion down-modulates CBL-B protein levels, suggesting that CBL-B regulates either the development or progression of CML. To assess the involvement of CBL-B in CML, bone marrow transduction and transplantation (BMT) studies were performed. Recipients of BCR-ABL-infected CBL-B(-/-) cells succumbed to a CML-like myeloproliferative disease with a longer latency than the wild-type recipients. Peripheral blood white blood cell numbers were reduced, as were splenic weights. Yet despite the reduced leukemic burden, granulocyte numbers were amplified throughout the animals. As well, CBLB(-/-) bone marrow (BM) cells possessed defective BM homing capabilities. From these results we concluded that CBL-B negatively regulates granulopoiesis and that prolonged latency in our CBL-B(-/-) BMT animals was a function of perturbed homing.To develop an in vitro model to study CBL-B function we established mouse embryonic fibroblasts (MEFs) deficient in CBL-B expression. Transduction of the wild-type and CBL-B-deficient MEFs with BCR-ABL did not confer transformation; nevertheless, the role of CBL-B in fibroblasts was evaluated. The CBL-B(-/-) MEFs showed enhanced chemotactic migration toward serum in both Transwell migration and time-lapse video microscopy studies. The biochemical response to serum was extensively evaluated leading to the development of a model. We predict that CBL-B deficiency either: (a) augments GRB2-associated binding protein 2 (GAB2) phosphorylation leading to enhanced extracellular signal-regulated kinase (ERK) and protein kinase B (PKB / Akt) signaling, or (b) alleviates negative control of Vav3 resulting in stimulation of Rho effectors. In either case, our results reveal a negative regulatory role for CBL-B in fibroblast migration. The two studies detailed herein expand our knowledge of CBL-B function. They strongly suggest that CBL-B can modulate granulocyte proliferation and point toward a role for CBL-B in the motility of numerous cell types.

Some disciplines are inherently complex and challenging to learn. This research attempts to design an instructional strategy for CBL systems to simplify learning certain complex domains. Firstly, problem transformation, a constructionist instructional technique, is used to promote active learning by encouraging students to construct more complex artefacts based on less complex ones. Scaffolding is used at the initial learning stages to alleviate the difficulty associated with complex transformation processes. The proposed instructional strategy brings various techniques together to enhance the learning experience. A functional prototype is implemented with Object-Z as the exemplar subject. Both objective and subjective evaluations using the prototype indicate that the proposed CBL system has a statistically significant impact on learning a complex domain. CBL systems include Learner models to provide adaptable support tailored to individual learners. Bayesian theory is used in general to manage uncertainty in Learner models. In this research, a fuzzy logic based locally intelligent Learner model is utilized. The fuzzy model is simple to design and implement, and easy to understand and explain, as well as efficient. Bayesian theory is used to complement the fuzzy model. Evaluation shows that the accuracy of the proposed Learner model is statistically significant. Further, opening Learner model reduces uncertainty, and the fuzzy rules are simple and resemble human reasoning processes. Therefore, it is argued that opening a fuzzy Learner model is both easy and effective. Scaffolding requires formative assessments. In this research, a confidence based multiple test marking scheme is proposed as traditional schemes are not suitable for measuring partial knowledge. Subjective evaluation confirms that the proposed schema is effective. Finally, a step-by-step methodology to transform simple UML class diagrams to Object-Z schemas is designed in order to implement problem transformation. This methodology could be extended to implement a semi-automated translation system for UML to Object Models.

<p>Proteins belonging to the Cbl family are multidomain scaffolds that participate in numerous processes, assembling signaling complexes and mediating attachment of ubiquitin to receptor and non-receptor tyrosine kinases.</p><p>We characterized a novel role for Cbl and Cbl-b in ligand-dependent internalization of growth factor receptors. Upon stimulation with epidermal growth factor (EGF), Cbl proteins associate with EGF receptor, become phosphorylated, and bind to the three SH3 domains of CIN85, which brings endophilins to the complex with active receptors. Endophilins can induce internalization of the plasma membrane, contributing to formation of clathrin-coated pits. We identified a minimal binding domain for CIN85 in the carboxyl termini of Cbl/Cbl-b and observed constitutive association between CIN85, Cbl/Cbl-b and oncogenically stimulated receptor tyrosine kinases. In addition to functioning as a ubiquitin ligase, Cbl forms a complex with CIN85 and endophilin, which is required for efficient endocytosis and downregulation of membrane receptors.</p><p>In EGF stimulated cells, we observed inducible modification of CIN85 and related CMS proteins by attachment of a single ubiquitin molecule. Monoubiquitination of CIN85 was mediated by the RING finger and dependent on the carboxyl terminal part of Cbl/Cbl-b, and demanded an intact carboxyl terminus of CIN85. Prolonged stimulation with EGF induced concomitant degradation of EGF receptors, Cbl, and monoubiquitinated forms of CIN85 in lysosomes.</p><p>Cbl regulates cytoskeletal processes in a variety of cell systems. We identified SH3P2, a protein with SH3 domain and ankyrin repeats, as a Cbl partner and described its phosphorylation by Src and its distribution in fibroblasts and osteoclasts. SH3P2 formed inducible complexes with Cbl and actin in spread cells and colocalized with dynamic actin structures.</p><p>Our data contribute to better understanding of the role of Cbl in downregulation of receptor tyrosine kinases as well as in controlling actin rearrangement.</p>

Proteins belonging to the Cbl family are multidomain scaffolds that participate in numerous processes, assembling signaling complexes and mediating attachment of ubiquitin to receptor and non-receptor tyrosine kinases. We characterized a novel role for Cbl and Cbl-b in ligand-dependent internalization of growth factor receptors. Upon stimulation with epidermal growth factor (EGF), Cbl proteins associate with EGF receptor, become phosphorylated, and bind to the three SH3 domains of CIN85, which brings endophilins to the complex with active receptors. Endophilins can induce internalization of the plasma membrane, contributing to formation of clathrin-coated pits. We identified a minimal binding domain for CIN85 in the carboxyl termini of Cbl/Cbl-b and observed constitutive association between CIN85, Cbl/Cbl-b and oncogenically stimulated receptor tyrosine kinases. In addition to functioning as a ubiquitin ligase, Cbl forms a complex with CIN85 and endophilin, which is required for efficient endocytosis and downregulation of membrane receptors. In EGF stimulated cells, we observed inducible modification of CIN85 and related CMS proteins by attachment of a single ubiquitin molecule. Monoubiquitination of CIN85 was mediated by the RING finger and dependent on the carboxyl terminal part of Cbl/Cbl-b, and demanded an intact carboxyl terminus of CIN85. Prolonged stimulation with EGF induced concomitant degradation of EGF receptors, Cbl, and monoubiquitinated forms of CIN85 in lysosomes. Cbl regulates cytoskeletal processes in a variety of cell systems. We identified SH3P2, a protein with SH3 domain and ankyrin repeats, as a Cbl partner and described its phosphorylation by Src and its distribution in fibroblasts and osteoclasts. SH3P2 formed inducible complexes with Cbl and actin in spread cells and colocalized with dynamic actin structures. Our data contribute to better understanding of the role of Cbl in downregulation of receptor tyrosine kinases as well as in controlling actin rearrangement.