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Vav guanine nucleotide exchange factors control B cell antigen receptor-induced Ca2+-signaling

dc.contributor.advisorWienands, Jürgen Prof. Dr.
dc.contributor.authorHitzing, Christoffer
dc.date.accessioned2016-03-15T11:11:09Z
dc.date.available2016-03-15T11:11:09Z
dc.date.issued2016-03-15
dc.identifier.urihttp://hdl.handle.net/11858/00-1735-0000-0028-86FF-2
dc.identifier.urihttp://dx.doi.org/10.53846/goediss-5568
dc.language.isoengde
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc570de
dc.titleVav guanine nucleotide exchange factors control B cell antigen receptor-induced Ca2+-signalingde
dc.typedoctoralThesisde
dc.contributor.refereeWienands, Jürgen Prof. Dr.
dc.date.examination2015-12-21
dc.description.abstractengDifferentiation of B cells into antibody secreting plasma cells is an indispensable step to cope with pathogens. Antigen binding to the B cell antigen receptor (BCR) initiates signaling cascades leading in combination with co-stimulatory signals to the differentiation of B cells. A hallmark of early B cell activation is the mobilization of Ca2+ from internal and external sources into the cytosol. Several proteins are reported to orchestrate Ca2+-mobilization downstream of the BCR including the adaptor protein SLP-65 that forms together with key signaling enzymes the central signaling complex in that context. Components of that multi-protein complex are members of the Vav protein guanine nucleotide exchange factor (GEF) family consisting of Vav1, Vav2 and Vav3, which based on genetic mouse models are predicted to fulfill important tasks in BCR signaling. However, the operating principle by which the Vav GEF family acts in BCR-induced Ca2+-mobilization is poorly understood. In my PhD project, I showed that Vav proteins constitute crucial signaling elements, controlling Ca2+-mobilization after BCR stimulation in B cells. For my investigations, I used the TALEN and CRISPR/Cas gene targeting technologies to generate new genetic model systems in a human B cell line. I found that especially Vav1 and Vav3, but not Vav2, are potent signaling factors in human B cells that enable BCR-induced Ca2+-mobilization. Genetic and biochemical approaches showed, that the functionality of Vav1 strictly depends on interactions mediated by its SH2-domain. In that context, I characterized a so far undiscovered interaction of Vav1 with the BCR. Furthermore, I showed that Vav1 localization within the BCR signalosome is not restricted to a specific signaling complex, since both exclusive binding to the BCR or the well-known Vav interaction partner SLP-65 enabled BCR-induced Ca2+-flux. In addition, I showed by mutational analysis that the functionality of Vav1 in BCR-induced Ca2+-mobilization strictly depends on two mechanisms carried out by different protein domains, the CH-domain and the DH-PH-ZF-domain unit. The DH-PH-ZF-domain unit is reported to be exclusively responsible for the binding and activation of Rho family G-proteins such as Rac1/2 and RhoA. In connection to that, I found that the structural integrity of the DH-PH-ZF-domain unit is a prerequisite for the functionality of Vav1 in BCR-induced Ca2+-mobilization, highlighting a potential role of small G-proteins in this process. The generation of a Rac2-deficient DG75 B cell line, however, showed no alteration of Ca2+-mobilization, so that other small G-proteins might be more important. The CH-domain supports the function of the DH-PH-ZF-domain unit probably by recruiting additional signaling factors, which need to be identified in future experiments. Collectively, my results demonstrate the paramount function of the Vav protein family in controlling the BCR-induced Ca2+-signaling cascade most likely by binding and activating of small Rho family G-proteins.de
dc.contributor.coRefereeWalter, Lutz Prof. Dr.
dc.subject.engVavde
dc.subject.engCalciumde
dc.subject.engBCR signalingde
dc.subject.engGEFde
dc.subject.engG-proteinsde
dc.identifier.urnurn:nbn:de:gbv:7-11858/00-1735-0000-0028-86FF-2-7
dc.affiliation.instituteGöttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften (GGNB)de
dc.subject.gokfullBiologie (PPN619462639)de
dc.identifier.ppn852141904


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