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| Author(s): |
Marina Gabriel Fontes
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2019-05-28 |
| Examining board members: |
Ana Paula Ulian de Araujo;
Antônio José da Costa Filho;
Eneida de Paula
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| Advisor: | Ana Paula Ulian de Araujo |
| Abstract | |
Septins are polymerizable GTPases. These cytoskeletal proteins are involved in several cellular processes in which they are associated to membranes, including cytokinesis, ciliogenesis and exocytosis. In order to perform these various functions, septins assemble into non-polar hetero-oligomers (complexes), which interact with each other forming higher-order structures such as filaments, ring and gauzes. These proteins are highly conserved in eukaryotes, yet the number of septin genes varies from one, in Chlamydomonas reinhardtii, to more than a dozen septin genes in humans. Previous studies from our research group described four septins in Schistosoma mansoni, named SmSEPT5, SmSEPT10, SmSEPT7.1 and SmSEPT7.2. Recently, it was verified that these proteins are capable of binding to model membranes, constituting a simpler model, when compared to human septins, to study the mechanism of membrane association. In this work, the influence of membrane curvature to the septin-lipid binding and the septin specificity to different phospholipids were investigated. In addition to S. mansoni septins, the septin complex from Ciona intestinalis was also included for comparative analyzes. Confocal fluorescence microscopy experiments showed that both SmSEPT10 and the septin complexes from S. mansoni and C. intestinalis bind, preferably, to membranes with 2 μm-1 curvatures (0,96 μm diameter). This tendency seems to be intrinsic to septins, as hetero-oligomers from other organisms had already presented the same binding preference. The capacity of an individual septin to distinguish curvatures is an indicative that the polymerization is not required for this mechanism. The interaction of these septins to the membrane models was only detected in the presence of dextrose, suggesting that this sugar acted in the protein stabilization, thus opening up new to study septin stability. These microscopy experiments, together with PIP Strips assays, demonstrated that the septin complex from C. intestinalis binds preferentially to phosphatidylserine, whereas septins from S. mansoni show a preference to phosphoinositides. Finally, preliminary assays with mutant constructions of SmSEPT10 C-terminal enabled the development of a hypothesis for the association mechanism of these proteins to membranes. (AU) | |
| FAPESP's process: | 16/13961-7 - Interactions of Schistosoma mansoni septins with membrane models |
| Grantee: | Marina Gabriel Fontes |
| Support Opportunities: | Scholarships in Brazil - Master |