2024-03-29T15:22:55Zhttps://www.tdx.cat/oai/requestoai:www.tdx.cat:10803/2839792017-08-31T11:01:40Zcom_10803_1col_10803_69
nam a 5i 4500
Proteïnes G
Proteínas G
G Proteins
Homeòstasi
Homeostasis
Citocinesi
Citocinesis
Cytokinesis
Involvement of the Microtubule-Regulated RhoGEF GEF-H1 in the G12 family signaling pathways
[Barcelona] :
Universitat de Barcelona,
2014
Accés lliure
http://hdl.handle.net/10803/283979
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AAMMDDs2014 sp ||||fsm||||0|| 0 eng|c
Garrido Antequera, Georgina,
autor
1 recurs en línia (233 pàgines)
Tesi realitzada a l'Institut de Biologia Molecular de Barcelona (IBMB)-CSIC
Tesi
Doctorat
Universitat de Barcelona. Departament de Genètica
2014
Universitat de Barcelona. Departament de Genètica
Tesis i dissertacions electròniques
Aragay i Combas, Anna M.,
supervisor acadèmic
Martínez Serra, Pedro,
supervisor acadèmic
TDX
Heterotrimeric G proteins are masters regulators of cell homeostasis. They coordinate the signaling between G protein coupled receptors (GPCRs) and their intracellular effectors. Heterotrimeric G proteins are composed of three subunits: G-alpha, G-beta, G-gamma. They function as a switches between an inactive GDP-bound state and an active GTP•bound state. Upon receptor activation, the G-alpha subunit undergoes a conformational change that leads to the exchange of GTP for GDP and the dissociation of the G-alpha subunit from the G-beta-gammadimer, allowing the subunits to activate their downstream effectors. The signal is terminated when the G-alpha subunit hydrolyzes its bound GTP to GDP and re-associates with G-beta-gamma. There are four subfamilies of G proteins: G-alpha (i), G-alpha(q), G-alpha(s) and G-alpha(12). Each subfamily can activate a different subset of effectors and signaling pathways. The subfamily of the G-alpha(12) protein is composed of two members: G-alpha(12) and G-alpha(13). They are involved in different processes such as embryonic development, cell growth, cell migration, angiogenesis processes and apoptosis. G-alpha(12) and G-alpha(13) have been linked to cellular events such as cytoskeletal rearrangements and cell proliferation through the activation of the small GTPase RhoA and moreover, they activate Rho principally through direct interaction with Rho-specific guanine nucleotide exchange factors (RhoGEFs). A growing number of RhoGEFs have recently been identified, with a majority as a members of the Dbl family of RhoGEF proteins. This proteins share in common a DH domain, the catalytic domain, and a PH domain, a pleckstrin homology domain. There are four RhoGEFs to be directly stimulated by the G-alpha(12/13) subfamily: p115RhoGEF, LARG, PDZRhoGEF and AKAP-Lbc. Three of them form the RH-RhoGEF subfamily because they share in common a RGS homology domain which is the implicated in their interaction with G12 proteins. GEF-Hl was discovered as a microtubule associated protein and belongs to the AKAP-Lbc subfamily. It has been reported to be regulated by its binding to microtubules, while microtubule-bound GEF-Hl is associated to have low activity its release from them leads to GEF-Hl activation and consequently, the activation of the small RhoGTPase RhoA. GEF-Hl can also be regulated by phosphorylation and several kinases can phosphorylate GEF-Hl in different moments of the cell. For instance, during cytokinesis GEF-Hl is phosphorylated by Aurora kinases and Cdk/Cyclin 8 in order to regulate its activity towars RhoA, due to be a high controlled spatiotemporal process. GEF-Hl is also considered a key player in the cross-talk of microtubules to actin dynamics and is reported to be involved in a variety of normal biological situations such as cell cycle regulation, and cell morphology, polarity and motility.
Conventionally G proteins have been linked with the plasma membrane where they exert their functions. However, several studies during the last years have shown that Gproteins can also regulate processes in other cellular compartments. Previous results showed that G-alpha(12) was important for cell division. Indeed, the results obtained during this thesis indicate that G-alpha(12) is associated with the spindle apparatus in the late stages of mitosis and also located at the midbody during cytokinesis. Interestingly, perturbation of GUn function results in aberrant mitosis with different phenotypes such as multi nucleation, apoptosis or failed cytokinesis. On the other hand, the results obtained shown that GEF•Hl would be a possible downstream effector for GUn signaling in mitosis due to the fact that GUn interacts and activates GEF-Hl. The interaction takes place trough the DH-PH domains of GEF-Hl and GUn was able to promote the release of GEF-Hl from microtubules, where GEF•Hl is found in its inactive form, and to stimulate GEF activity of GEFHI. Furthermore, colocalization experiments showed that GU12 and GEF-Hl are located in the midbody during cytokinesis. So, we propose a mechanism for the interaction between GEF-Hl and G-alpha(12) during cytokinesis where sequentially G-alpha(12) would activate GEF-Hl in first place, and secondly G-alpha(12) would activate LARG, which is needed to complete the absicission process and is also stimulated by GUn.
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