RESUMO
Amino acids and polyamines are involved in relevant processes for the parasite Trypanosoma cruzi, like protein synthesis, stress resistance, life cycle progression, infection establishment and redox balance, among others. In addition to the biosynthetic routes of amino acids, T. cruzi possesses transport systems that allow the active uptake from the extracellular medium; and in the case of polyamines, the uptake is the unique way to obtain these compounds. The TcAAAP protein family is absent in mammals and its members are responsible for amino acid and derivative uptake, thus the TcAAAP permeases are not only interesting and promising therapeutic targets but could also be used to direct the entry of toxic compounds into the parasite. Although there is a treatment available for Chagas disease, its limited efficacy in the chronic stage of the disease, as well as the side effects reported, highlight the urgent need to develop new therapies. Discovery of new drugs is a slow and cost-consuming process, and even during clinical trials the drugs can fail. In this context, drug repositioning is an interesting and recommended strategy by the World Health Organization since costs and time are significantly reduced. In this article, amino acids and polyamines transport and their potential as therapeutic targets will be revised, including examples of synthetic drugs and drug repurposing.
Assuntos
Sistemas de Transporte de Aminoácidos/antagonistas & inibidores , Proteínas de Transporte de Cátions/antagonistas & inibidores , Tripanossomicidas/farmacologia , Trypanosoma cruzi/efeitos dos fármacos , Animais , Reposicionamento de Medicamentos , Poliaminas/metabolismoRESUMO
BACKGROUND: Trypanosoma cruzi, the etiological agent of Chagas disease, uses proline as its main carbon source, essential for parasite growth and stage differentiation in epimastigotes and amastigotes. Since proline is involved in many essential biological processes in T. cruzi, its transport and metabolism are interesting drug targets. METHODS: Four synthetic proline analogues (ITP-1B/1C/1D/1G) were evaluated as inhibitors of proline transport mediated through the T. cruzi proline permease TcAAAP069. The trypanocidal activity of the compounds was also assessed. RESULTS: The compounds ITP-1B and ITP-1G inhibited proline transport mediated through TcAAAP069 permease in a dose-dependent manner. The analogues ITP-1B, -1D and -1G had trypanocidal effect on T. cruzi epimastigotes with IC50 values between 30 and 40µM. However, only ITP-1G trypanocidal activity was related with its inhibitory effect on TcAAAP069 proline transporter. Furthermore, this analogue strongly inhibited the parasite stage differentiation from epimastigote to metacyclic trypomastigote. Finally, compounds ITP-1B and ITP-1G were also able to inhibit the transport mediated by other permeases from the same amino acid permeases family, TcAAAP. CONCLUSIONS: It is possible to design synthetic amino acid analogues with trypanocidal activity. The compound ITP-1G is an interesting starting point for new trypanocidal drug design which is also an inhibitor of transport of amino acids and polyamines mediated by permeases from the TcAAAP family, such as proline transporter TcAAAP069 among others. GENERAL SIGNIFICANCE: The Trypanosoma cruzi amino acid transporter family TcAAAP constitutes a multiple and promising therapeutic target for the development of new treatments against Chagas disease.
Assuntos
Sistemas de Transporte de Aminoácidos Neutros/genética , Doença de Chagas/tratamento farmacológico , Prolina/farmacologia , Tripanossomicidas/farmacologia , Sistemas de Transporte de Aminoácidos Neutros/metabolismo , Aminoácidos/genética , Animais , Doença de Chagas/genética , Doença de Chagas/parasitologia , Humanos , Prolina/análogos & derivados , Trypanosoma cruzi/efeitos dos fármacos , Trypanosoma cruzi/patogenicidadeRESUMO
Trypanosoma cruzi is the etiological agent of Chagas disease. During its life cycle, it alternates among vertebrate and invertebrate hosts. Metabolic flexibility is a main biochemical characteristic of this parasite, which is able to obtain energy by oxidizing a variety of nutrients that can be transported from the extracellular medium. Moreover, several of these metabolites, more specifically amino acids, have a variety of functions beyond being sources of energy. Branched chain amino acids (BCAA), beyond their role in ATP production, are involved in sterol biosynthesis; for example, leucine is involved as a negative regulator of the parasite differentiation process occurring in the insect midgut. BCAA are essential metabolites in most nonphotosynthetic eukaryotes, including trypanosomes. In view of this, the metabolism of BCAA in T. cruzi depends mainly on their transport into the cell. In this work, we kinetically characterized the BCAA transport in T. cruzi epimastigotes. Our data point to BCAA as being transported by a single saturable transport system able to recognize leucine, isoleucine and valine. In view of this, we used leucine to further characterize this system. The transport increased linearly with temperature from 10 to 45 °C, allowing the calculation of an activation energy of 51.30 kJ/mol. Leucine uptake was an active process depending on ATP production and a H(+) gradient, but not on a Na(+) or K(+) gradient at the cytoplasmic membrane level.
Assuntos
Aminoácidos de Cadeia Ramificada/química , Aminoácidos de Cadeia Ramificada/metabolismo , Membrana Celular/metabolismo , Trypanosoma cruzi/metabolismo , Trifosfato de Adenosina/metabolismo , Sistemas de Transporte de Aminoácidos , Animais , Doença de Chagas/parasitologia , Isoleucina/metabolismo , Isoleucina/farmacologia , Cinética , Leucina/metabolismo , Leucina/farmacologia , Temperatura , Trypanosoma cruzi/efeitos dos fármacos , Valina/metabolismo , Valina/farmacologiaRESUMO
The sodium coupled neutral amino acid transporter 2 (SNAT2/SAT2/ATA2) is expressed in the mammary gland (MG) and plays an important role in the uptake of alanine and glutamine which are the most abundant amino acids transported into this tissue during lactation. Thus, the aim of this study was to assess the amount and localization of SNAT2 before delivery and during lactation in rat MG, and to evaluate whether prolactin and the dietary protein/carbohydrate ratio might influence SNAT2 expression in the MG, liver and adipose tissue during lactation. Our results showed that SNAT2 protein abundance in the MG increased during lactation and this increase was maintained along this period, while 24 h after weaning it tended to decrease. To study the effect of prolactin on SNAT2 expression, we incubated MG explants or T47D cells transfected with the SNAT2 promoter with prolactin, and we observed in both studies an increase in the SNAT2 expression or promoter activity. Consumption of a high-protein/low carbohydrate diet increased prolactin concentration, with a concomitant increase in SNAT2 expression not only in the MG during lactation, but also in the liver and adipose tissue. There was a correlation between SNAT2 expression and serum prolactin levels depending on the amount of dietary protein/carbohydrate ratio consumed. These findings suggest that prolactin actively supports lactation providing amino acids to the gland through SNAT2 for the synthesis of milk proteins.
Assuntos
Sistema A de Transporte de Aminoácidos/metabolismo , Carboidratos da Dieta/metabolismo , Proteínas Alimentares/metabolismo , Lactação/metabolismo , Glândulas Mamárias Animais/metabolismo , Prolactina/metabolismo , Tecido Adiposo/metabolismo , Sistema A de Transporte de Aminoácidos/genética , Fenômenos Fisiológicos da Nutrição Animal , Animais , Carboidratos da Dieta/administração & dosagem , Proteínas Alimentares/administração & dosagem , Feminino , Regulação da Expressão Gênica , Lactação/sangue , Lactação/genética , Fígado/metabolismo , Fenômenos Fisiológicos da Nutrição Materna , Proteínas do Leite/biossíntese , Estado Nutricional , Gravidez , Prolactina/sangue , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismo , Ratos Wistar , Técnicas de Cultura de Tecidos , Transfecção , DesmameRESUMO
Rhizobia are bacteria in the α-proteobacterial genera Rhizobium, Sinorhizobium, Mesorhizobium, Azorhizobium and Bradyrhizobium that reduce (fix) atmospheric nitrogen in symbiotic association with a compatible host plant. In free-living and/or symbiotically associated rhizobia, amino acids may, in addition to their incorporation into proteins, serve as carbon, nitrogen or sulfur sources, signals of cellular nitrogen status and precursors of important metabolites. Depending on the rhizobia-host plant combination, microsymbiont amino acid metabolism (biosynthesis, transport and/or degradation) is often crucial to the establishment and maintenance of an effective nitrogen-fixing symbiosis and is intimately interconnected with the metabolism of the plant. This review summarizes past findings and current research directions in rhizobial amino acid metabolism and evaluates the genetic, biochemical and genome expression studies from which these are derived. Specific sections deal with the regulation of rhizobial amino acid metabolism, amino acid transport, and finally the symbiotic roles of individual amino acids in different plant-rhizobia combinations.
Assuntos
Aminoácidos/metabolismo , Fabaceae/microbiologia , Fixação de Nitrogênio/fisiologia , Rhizobiaceae/metabolismo , Simbiose/fisiologia , Transporte Biológico Ativo/fisiologiaRESUMO
Insulin and insulin-like growth factor 1 (IGF-I) are capable of activating similar intracellular pathways. Insulin acts mainly through its own receptor, but can also activate the IGF-I receptor (IGF-IR). The aim of this study was to investigate the involvement of the IGF-IR in the effects of insulin and IGF-I on the membrane potential of immature Sertoli cells in whole seminiferous tubules, as well as on calcium, amino acid, and glucose uptake in testicular tissue of immature rats. The membrane potential of the Sertoli cells was recorded using a standard single microelectrode technique. In calcium uptake experiments, the testes were pre-incubated with (45)Ca(2+), with or without JB1 (1 µg/mL), and then incubated with insulin (100 nM) or IGF-I (15 nM). In amino acid and glucose uptake experiments, the gonads were pre-incubated with or without JB1 (1 µg/mL) and then incubated with radiolabeled amino acid or glucose analogues in the presence of insulin (100 nM) or IGF-I (15 nM). The blockade of IGF-IR with JB1 prevented the depolarising effects of both insulin and IGF-I on membrane potential, as well as the effect of insulin on calcium uptake. JB1 also inhibited the effects of insulin and IGF-I on glucose uptake. The effect of IGF-I on amino acid transport was inhibited in the presence of JB1, whereas the effect of insulin was not. We concluded that while IGF-I seems to act mainly through its cognate receptor to induce membrane depolarisation and calcium, amino acid and glucose uptake, insulin appears to be able to elicit its effects through IGF-IR, in seminiferous tubules from immature rats.
Assuntos
Fator de Crescimento Insulin-Like I/metabolismo , Insulina/metabolismo , Receptor IGF Tipo 1/metabolismo , Túbulos Seminíferos/metabolismo , Aminoácidos/metabolismo , Animais , Transporte Biológico , Cálcio/metabolismo , Membrana Celular/metabolismo , Glucose/metabolismo , Masculino , Potenciais da Membrana , Ratos , Ratos Wistar , Células de Sertoli/metabolismoRESUMO
Soybean plants cultivated with 50, 100 and 200 mM of NaCl, revealed that root growth was less affected by salinity than shoots. Salinity led to a reduction in leaf area and an increase in water content of the roots. These factors could contribute to the adaptation of the plant, improving its hydration. Although nitrate and free amino acid levels were reduced by salt treatment in roots, protein content of leaves was not altered. Salinity led to alterations in xylem amino acid composition, with increases in Ser, Ala, Gaba and Pro and a decrease in Asn. Similar changes were seen for Asn and Ser in roots together with a much stronger increase in Gaba. It is suggested that the decline in Asn reflects its conversion to Ala and Gaba (via Glu) in the roots while the increase in Pro and Gaba could be related to the adaptation of the plant to salinity.