Publicação
Study of the influence of lipid rafts in acetic acid-induced apoptosis
| Resumo: | Lipid rafts are sphingolipid-sterol rich micro-domains of the plasma membrane that have been associated with different cellular processes, including apoptosis. During the past years, yeast has been successfully established as a model to study mechanisms of programmed cell death in mammalian cells. Saccharomyces cerevisiae commits to cell death showing typical hallmarks of metazoan apoptosis in response to different stimuli. Gup1p, a pleiotropic O-acyltransferase first associated with glycerol metabolism and transport, is involved in lipid metabolism, rafts integrity and assembly, as well as in GPI anchor remodeling, among a wide range of cellular processes. While Gpd1p/Gpd2p are the two isoforms of glycerol-3-phosphate dehydrogenase that have a prime role in the production of glycerol, Rvs161p is a lipid raft protein mainly involved in the regulation of actin cytoskeleton polarization and secretory vesicle trafficking. Actin cytoskeleton together with vesicle trafficking have been suggested to play a crucial role in yeast apoptosis. Therefore, it is conceivable that lipid rafts may also play a role in yeast cell death and understanding their function in such process in yeast may provide further insights on their role in mammalian apoptosis. For this purpose we used two known apoptosis inducing conditions, chronological aging and acetic acid, and analyzed several apoptotic markers in Δgup1, Δgpd1Δgpd2 and Δrvs161 mutant strains. We found that Δgup1 presents a significantly reduced chronological life span as compared to Wt and is also highly sensitive to acetic acid treatment. According to the apoptotic markers analyzed, cells lacking GUP1 seem to be incapable of undergoing apoptosis. Instead this mutant appears to be experiencing a necrotic cell death process. The Δgpd1Δgpd2 (but not single mutants) and Δrvs161 mutant strains are also sensitive to acetic acid. However, the apoptotic markers examined suggest that these mutants die by apoptosis, differently from that we observed for gup1 mutant. The ergosterol distribution in Wt and in the acetic acid-sensitive mutant strains gup1, Δgpd1Δgpd2 and Δrvs161 was subsequently observed by filipin staining. An altered ergosterol distribution was visualized in all mutants studied, particularly in gup1 mutant. We also observed that acetic acid induces a rearrangement in the distribution of ergosterol. Altogether, our results indicate that lipid rafts seems to be a key component in apoptotic induction/signaling, probably even essential in some circumstances for the correct development of apoptosis in yeast. |
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| Autores principais: | Moreira, Joana Isabel da Silva Tulha |
| Ano: | 2011 |
| 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: | Lipid rafts are sphingolipid-sterol rich micro-domains of the plasma membrane that have been associated with different cellular processes, including apoptosis. During the past years, yeast has been successfully established as a model to study mechanisms of programmed cell death in mammalian cells. Saccharomyces cerevisiae commits to cell death showing typical hallmarks of metazoan apoptosis in response to different stimuli. Gup1p, a pleiotropic O-acyltransferase first associated with glycerol metabolism and transport, is involved in lipid metabolism, rafts integrity and assembly, as well as in GPI anchor remodeling, among a wide range of cellular processes. While Gpd1p/Gpd2p are the two isoforms of glycerol-3-phosphate dehydrogenase that have a prime role in the production of glycerol, Rvs161p is a lipid raft protein mainly involved in the regulation of actin cytoskeleton polarization and secretory vesicle trafficking. Actin cytoskeleton together with vesicle trafficking have been suggested to play a crucial role in yeast apoptosis. Therefore, it is conceivable that lipid rafts may also play a role in yeast cell death and understanding their function in such process in yeast may provide further insights on their role in mammalian apoptosis. For this purpose we used two known apoptosis inducing conditions, chronological aging and acetic acid, and analyzed several apoptotic markers in Δgup1, Δgpd1Δgpd2 and Δrvs161 mutant strains. We found that Δgup1 presents a significantly reduced chronological life span as compared to Wt and is also highly sensitive to acetic acid treatment. According to the apoptotic markers analyzed, cells lacking GUP1 seem to be incapable of undergoing apoptosis. Instead this mutant appears to be experiencing a necrotic cell death process. The Δgpd1Δgpd2 (but not single mutants) and Δrvs161 mutant strains are also sensitive to acetic acid. However, the apoptotic markers examined suggest that these mutants die by apoptosis, differently from that we observed for gup1 mutant. The ergosterol distribution in Wt and in the acetic acid-sensitive mutant strains gup1, Δgpd1Δgpd2 and Δrvs161 was subsequently observed by filipin staining. An altered ergosterol distribution was visualized in all mutants studied, particularly in gup1 mutant. We also observed that acetic acid induces a rearrangement in the distribution of ergosterol. Altogether, our results indicate that lipid rafts seems to be a key component in apoptotic induction/signaling, probably even essential in some circumstances for the correct development of apoptosis in yeast. |
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