Publicação
Targeting human aquaporin function : physiological and chemical approaches
| Resumo: | Aquaporins (AQPs) are a group of small membrane proteins belonging to a highly conserved family of membrane proteins called MIPs (Major Intrinsic Proteins) that are responsible for the bidirectional transport of wate (orthodox aquaporins) and also small uncharged solutes (aquaglyceroporins) across cell membranes, in response to osmotic or solute gradients. Rapid water flux across membranes is crucial to maintain the water homeostasis in many epithelia and endothelia involved in fluid transport. In addition, due to the unique ability of aquaglyceroporins to transport glycerol in addition to water, they have important roles in glycerol metabolism and skin hydration in non-fluid transporting tissues such as skin, fat and liver. The thesis introduction (Chapter 1) presents an overview of aquaporins structure, their main biological functions and related pathologies, with special emphasis on the so far described mechanisms of regulation. In the first part of this thesis (Chapter 2), we report the discovery of a new role for Aquaporin-5 (AQP5, an orthodox aquaporin) in adipocyte biology, where Aquaporin-7 (AQP7, an aquaglyceroporin) has been the mainly characterized protein in adipose tissue responsible for glycerol efflux. A better understanding of aquaporin regulation and gating would allow manipulation of their activity facilitating the identification of new putative modulators. A cellular model optimized to assess the function of aquaporins and discriminate individually each isoform, instead of mammalian cells where more than one isoform is usually expressed, is a useful tool to study aquaporin regulation. The second part of this thesis (Chapter 3) is dedicated to the functional characterization of different mammalian aquaporin isoforms (AQP3, AQP5, AQP7 and AQP10), using a yeast heterologous expression system devoided of endogenous aquaporins, a background where analysis is unlikely to be compromised by the co-expression of other aquaporin isoforms. Using the stopped-flow technique to evaluate the channel permeability for water and for glycerol, we were able to disclose gating mechanisms of aquaporin isoforms, being given special emphasis to the regulation by pH and phosphorylation. In the third part of this thesis (Chapter 4), a screening of several small gold compounds as inhibitors for Aquaporin-3 (AQP3, an aquaglyceroporin) was performed aiming at identifying new modulators with potential therapeutic use. |
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| Autores principais: | Mósca, Andreia F |
| Assunto: | Teses de doutoramento - 2018 |
| Ano: | 2018 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Aquaporins (AQPs) are a group of small membrane proteins belonging to a highly conserved family of membrane proteins called MIPs (Major Intrinsic Proteins) that are responsible for the bidirectional transport of wate (orthodox aquaporins) and also small uncharged solutes (aquaglyceroporins) across cell membranes, in response to osmotic or solute gradients. Rapid water flux across membranes is crucial to maintain the water homeostasis in many epithelia and endothelia involved in fluid transport. In addition, due to the unique ability of aquaglyceroporins to transport glycerol in addition to water, they have important roles in glycerol metabolism and skin hydration in non-fluid transporting tissues such as skin, fat and liver. The thesis introduction (Chapter 1) presents an overview of aquaporins structure, their main biological functions and related pathologies, with special emphasis on the so far described mechanisms of regulation. In the first part of this thesis (Chapter 2), we report the discovery of a new role for Aquaporin-5 (AQP5, an orthodox aquaporin) in adipocyte biology, where Aquaporin-7 (AQP7, an aquaglyceroporin) has been the mainly characterized protein in adipose tissue responsible for glycerol efflux. A better understanding of aquaporin regulation and gating would allow manipulation of their activity facilitating the identification of new putative modulators. A cellular model optimized to assess the function of aquaporins and discriminate individually each isoform, instead of mammalian cells where more than one isoform is usually expressed, is a useful tool to study aquaporin regulation. The second part of this thesis (Chapter 3) is dedicated to the functional characterization of different mammalian aquaporin isoforms (AQP3, AQP5, AQP7 and AQP10), using a yeast heterologous expression system devoided of endogenous aquaporins, a background where analysis is unlikely to be compromised by the co-expression of other aquaporin isoforms. Using the stopped-flow technique to evaluate the channel permeability for water and for glycerol, we were able to disclose gating mechanisms of aquaporin isoforms, being given special emphasis to the regulation by pH and phosphorylation. In the third part of this thesis (Chapter 4), a screening of several small gold compounds as inhibitors for Aquaporin-3 (AQP3, an aquaglyceroporin) was performed aiming at identifying new modulators with potential therapeutic use. |
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