Heteromeric composition of the Kv 1.3 channelosome = Composició heteromèrica del canalosoma Kv1.3
[eng] Ion channels are transmembrane proteins containing aqueous pores which, once open, permit the pass of ions through the plasma membrane. This ion flux takes places following the electrochemical gradient for the specific ion. Kv1.3 is a voltage-gated potassium channel which is member of the Shak...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2018 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/127722 |
| Acceso en línea: | https://hdl.handle.net/2445/127722 http://hdl.handle.net/10803/665245 |
| Access Level: | acceso abierto |
| Palabra clave: | Canals de potassi Membranes cel·lulars Proteïnes de membrana Potassium channels Cell membranes Membrane proteins |
| Sumario: | [eng] Ion channels are transmembrane proteins containing aqueous pores which, once open, permit the pass of ions through the plasma membrane. This ion flux takes places following the electrochemical gradient for the specific ion. Kv1.3 is a voltage-gated potassium channel which is member of the Shaker superfamily. Its basic structure consists in a protein with six transmembrane domains, while the functional channel is formed by 4 copies of this protein. Kv1.3 participates in a great amount of physiological functions: nervous system, immune system, insulin signaling or cell proliferation. In the immune system, Kv1.3 is highly expressed both in lymphocytes as well as in mononuclear phagocytes. In both cell types, Kv1.3 regulates the immune activation and cell proliferation. Moreover, Kv1.3 is coexpressed with other ion channel proteins like Kv1.5 or KCNE4 in the immune cells. Kv1.5 is able to heteromerize with Kv1.3, generating heterotetramers with variable stoichiometries. Those heterotetramers produce intermediate phenotypes depending on the ratio of the subunits that generate them. On the other side, KCNE4 may interact with Kv1.3, but not with Kv1.5. Kv1.3 is greatly inhibited by the association with either of the two proteins. In the present thesis we focus in characterizing these interactions and the importance of stoichiometry in their effects. We demonstrate that the associations between Kv1.3 and Kv1.5; and between Kv1.3 and KCNE4 take place in immune cells. Moreover, by using a fusion protein we get to fix the stoichiometry of the Kv1.3-Kv1.5 complex to 1:1. With this stoichiometry, Kv1.5 acts as a dominant negative toward Kv1.3 in the complex. Further interactions are characterized by using several chimeric proteins. By using those chimaeras, it is revealed that the carboxyterminal domain is necessary for the correct function of the channel. On the other hand, we demonstrate that KCNE4 is able to interact with Kv1.3 regardless of Kv1.5 presence. Furthermore, the presence of Kv1.5 in the Kv1.3-KCNE4 interaction results in this association potentiating the function of the channel, instead of inhibiting it. These results are replicated both in heterologous systems as well as in native cells. This discovery presents a new paradigm by which the association with several modulatory proteins may result in the modification of the effect of each one of them. Taking into account the sheer number of different ion channel subunits, the number of different potential phenotypes is increased by a huge margin. KCNE1 is a regulatory subunit, as well as KCNE4. Unlike KCNE4, though, KCNE1 can interact with Kv1.5. In the present thesis we demonstrate for the first time that KCNE1 is not only able to associate with Kv1.5, but to potentiate its activity by a huge amount. This interaction also seems to affect the membrane microdomain targeting of Kv1.5 Finally, the 4 studied proteins are expressed in T lymphocytes, which are the main actors in the pathogenicity of autoimmune diseases. Therefore, we genotyped those genes in multiple sclerosis patients to identify different polymorphisms which could be linked to immune overactivity. After analyzing the different polymorphisms, we located some which could be of special relevance for the physiopathology of autoimmune diseases. |
|---|