Publicação
Saccharomyces cerevisiae strains expressing human KRAS as tools for targeting therapeutic anti-EGFR-RAS pathway antibody - drugs
| Resumo: | Fundamental cellular processes appear to be highly conserved between Saccharomyces cerevisiae and other more complex Eukaryotic species, including humans. “Humanized yeast systems” emerged as a tool to study molecular aspects of human pathologies. The present work aimed at contributing to build and validate a large high throughput platform of yeast strains displaying phenotypes that can enable further testing galectin-related drugs and peptides. This platform was designed to consist of two types of strains, the ones expressing human galectins and the ones expressing these together with the human KRAS cDNA. The rationale behind this relates with the putative dialogue between Galectins and RAS signaling pathway in mammals. Considering that EGFR mediates KRAS signaling and that yeast also harbors a RAS signaling pathway, the “humanized yeasts” expressing KRAS were used to identify the yeast target of anti-EGFR. Furthermore, it was also used for phenotyping the most well-known biological processes known to be controlled by RAS pathway. On the other hand, considering that the deletion of GUP1 in S. cerevisiae increases the resistance to the oncological drug Imatinib, the similarities between the phenotypes associated to the deletion of RAS and GUP genes were also verified. Two Hsp70, Ssa2p and Ssb2p and one glyceraldehyde-3-phosphate dehydrogenase Tdh3p, were identified as EGFR-like proteins. The subsequent alignments analysis between EGFR and these proteins revealed that Ssb2p and its very close homologue Ssa2p present some homology with EGFR sequence, namely at the level of three EGFR conserved amino acids known to be responsible for the interaction with the anti-EGFR antibody Cetuximab used in cancer treatment. This and other lines of evidence support Ssb2p and/or Ssa2p as good candidates for EGFR homology. The phenotypic tests revealed that both the deletions of GUP and RAS genes promote a reduction in chronological life span and cell size, except in the case of Δras2 strain, whose cells were bigger than wild type control. Nutrient depletion (carbon) promoted replication stress in Δras2 cells that failed to enter into G1 arrest, and were blocked in S phase, concurring with the bigger size of Δras2 cells and their short lifespan. Moreover, the cells with GUP genes deleted, in opposition to RAS mutants, showed ability to adhere to solid nitrogen-deficient medium. Neither RAS nor GUP mutants were able to invade or filament under these conditions. With this work we were able to determine the possible homologue of EGFR, many times associated with cancer pathologies, and contributed to gain insights on RAS and GUP genes common phenotypes. In conclusion, the present work opens doors to future discovery of new pathways in yeast, in addition to showing that S. cerevisiae is a suitable model to create a platform to explore therapeutic drugs/antibodies. |
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| Autores principais: | Brito, Ana Sofia da Costa e |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Fundamental cellular processes appear to be highly conserved between Saccharomyces cerevisiae and other more complex Eukaryotic species, including humans. “Humanized yeast systems” emerged as a tool to study molecular aspects of human pathologies. The present work aimed at contributing to build and validate a large high throughput platform of yeast strains displaying phenotypes that can enable further testing galectin-related drugs and peptides. This platform was designed to consist of two types of strains, the ones expressing human galectins and the ones expressing these together with the human KRAS cDNA. The rationale behind this relates with the putative dialogue between Galectins and RAS signaling pathway in mammals. Considering that EGFR mediates KRAS signaling and that yeast also harbors a RAS signaling pathway, the “humanized yeasts” expressing KRAS were used to identify the yeast target of anti-EGFR. Furthermore, it was also used for phenotyping the most well-known biological processes known to be controlled by RAS pathway. On the other hand, considering that the deletion of GUP1 in S. cerevisiae increases the resistance to the oncological drug Imatinib, the similarities between the phenotypes associated to the deletion of RAS and GUP genes were also verified. Two Hsp70, Ssa2p and Ssb2p and one glyceraldehyde-3-phosphate dehydrogenase Tdh3p, were identified as EGFR-like proteins. The subsequent alignments analysis between EGFR and these proteins revealed that Ssb2p and its very close homologue Ssa2p present some homology with EGFR sequence, namely at the level of three EGFR conserved amino acids known to be responsible for the interaction with the anti-EGFR antibody Cetuximab used in cancer treatment. This and other lines of evidence support Ssb2p and/or Ssa2p as good candidates for EGFR homology. The phenotypic tests revealed that both the deletions of GUP and RAS genes promote a reduction in chronological life span and cell size, except in the case of Δras2 strain, whose cells were bigger than wild type control. Nutrient depletion (carbon) promoted replication stress in Δras2 cells that failed to enter into G1 arrest, and were blocked in S phase, concurring with the bigger size of Δras2 cells and their short lifespan. Moreover, the cells with GUP genes deleted, in opposition to RAS mutants, showed ability to adhere to solid nitrogen-deficient medium. Neither RAS nor GUP mutants were able to invade or filament under these conditions. With this work we were able to determine the possible homologue of EGFR, many times associated with cancer pathologies, and contributed to gain insights on RAS and GUP genes common phenotypes. In conclusion, the present work opens doors to future discovery of new pathways in yeast, in addition to showing that S. cerevisiae is a suitable model to create a platform to explore therapeutic drugs/antibodies. |
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