ABSTRACT
Alanine-serine-cysteine transporter 2 (ASCT2) is reported to participate in the progression of tumors and metabolic diseases. It is also considered to play a crucial role in the glutamate-glutamine shuttle of neuroglial network. However, it remains unclear the involvement of ASCT2 in neurological diseases such as Parkinson's disease (PD). In this study, we demonstrated that high expression of ASCT2 in the plasma samples of PD patients and the midbrain of MPTP mouse models is positively correlated with dyskinesia. We further illustrated that ASCT2 expressed in astrocytes rather than neurons significantly upregulated in response to either MPP+ or LPS/ATP challenge. Genetic ablation of astrocytic ASCT2 alleviated the neuroinflammation and rescued dopaminergic (DA) neuron damage in PD models in vitro and in vivo. Notably, the binding of ASCT2 to NLRP3 aggravates astrocytic inflammasome-triggered neuroinflammation. Then a panel of 2513 FDA-approved drugs were performed via virtual molecular screening based on the target ASCT2 and we succeed in getting the drug talniflumate. It is validated talniflumate impedes astrocytic inflammation and prevents degeneration of DA neurons in PD models. Collectively, these findings reveal the role of astrocytic ASCT2 in the pathogenesis of PD, broaden the therapeutic strategy and provide a promising candidate drug for PD treatment.
ABSTRACT
Glutamine plays a significant role in metabolism of protein and energy in cells. However, glutamine must be transported into cells to be utilized via the specific vector on cell membrane. The most important transporter is the Na ∗ dependent glutamine vector alanine-serine-cysteine transporter 2 (ASCT2). The regulation of ASCT2 biological function is closely related to human health. The ASCT2 is not only broadly expressed in normal tissues and organs but increases its expression in cancer to fulfill the augmented glutamine demand. Interactions with proteins and post-translational modifications regulate ASCT2 stability and transport activity. Two asparagine residues, namely N163 and N212, are the sites of glycosylation that have responsibility for the definitive localization into the plasma membrane. However, it has little effect on the intrinsic transport function of ASCT2. This review summarizes the regulation of biological function of ASCT2 and its significance in the treatment of disease.
ABSTRACT
Solute carrier (SLC) transporters meditate many essential physiological functions, including nutrient uptake, ion influx/efflux, and waste disposal. In its protective role against tumors and infections, the mammalian immune system coordinates complex signals to support the proliferation, differentiation, and effector function of individual cell subsets. Recent research in this area has yielded surprising findings on the roles of solute carrier transporters, which were discovered to regulate lymphocyte signaling and control their differentiation, function, and fate by modulating diverse metabolic pathways and balanced levels of different metabolites. In this review, we present current information mainly on glucose transporters, amino-acid transporters, and metal ion transporters, which are critically important for mediating immune cell homeostasis in many different pathological conditions.
ABSTRACT
OBJECTIVE: ASCT2 and LAT1 are aminoacid transporters involved in glutamine transport and play a role in tumor growth. Previous studies have shown an association of ASCT2 to cell proliferation through the mechanistic Target of Rapamycin (mTOR) translational machinery; LAT1 has been shown as a prognostic marker due to its relation to tumor invasion, microscopic vascular invasion and metastasis. This study analyzed the gene expression of ASCT2 and LAT1 in astrocytomas of different grades and how this correlates to clinical outcome in glioblastoma patients. METHOD: This is an observational study with ASCT2 and LAT1 mRNA expression analysis in 153 samples of human astrocytomas, distributed in different World Health Organization (WHO) grades of malignancy (23 at grade I or pilocytic astrocytoma, 26 at grade II or low-grade astrocytoma, 18 at grade III or anaplastic astrocytoma, 86 at grade IV astrocytoma or glioblastoma (AGIV or GBM)); these were compared to 22 non-neoplastic brain samples. RESULTS: Significant hyperexpression of both genes was observed particularly in malignant astrocytomas (GIII & GBM). Moreover, LAT1 hyperexpression impacted negatively in the overall survival in a subset of GBM patients. CONCLUSION: LAT1 is more expressed in higher grade astrocytomas. It leads to a poorer prognosis among GBM patients and may be a potential therapeutical target.
OBJETIVO: ASCT2 e LAT1 são transportadores de aminoácidos envolvidos no transporte de glutamina e desempenham um papel no crescimento tumoral. Estudos prévios mostraram uma associação de ASCT2 com proliferação celular através da maquinaria de tradução do mTOR; tem sido mostrado que o LAT1 é um marcador prognóstico devido à sua relação com invasão tumoral, invasão vascular microscópica e metástase. Este estudo analisou a expressão gênica de ASCT2 e LAT1 em astrocitomas de diferentes graus e sua correlação com desfecho clínico em pacientes com glioblastoma. METODO: Este é um estudo observacional com análise de expressão de RNAm de ASCT2 e LAT1 em 153 amostras de astrocitomas humanos, distribuídas em diferentes graus de malignidade segundo a OMS (23 astrocitomas de grau I ou astrocitoma pilocítico, 26 de astrocitoma de grau II ou astrocitoma de baixo grau, 18 de astrocitoma de grau III ou astrocitoma anaplásico, 86 de astrocitoma de grau IV ou glioblastoma (AGIV ou GBM); estes foram comparados com 22 amostras cerebrais não neoplásicas. RESULTADOS: Foi observada uma hiperexpressão de ambos os genes, particularmente nos astrocitomas malignos (GIII & GBM). Além disso, a hiperexpressão LAT1 impactou negativamente na sobrevida global em um grupo de pacientes com GBM. CONCLUSÃO: LAT1 é mais expresso em astrocitomas de grau maior. Isso leva a um pior prognóstico entre os pacientes com GBM e pode ser um potencial alvo terapêutico.
Subject(s)
Humans , Astrocytoma , Gene Expression , Glioblastoma/pathology , Large Neutral Amino Acid-Transporter 1/analysis , GlutamineABSTRACT
Objective:Glutamine is the main oxidative fuel of the enterocyte which enters the enterocyte primarily via amino acid transporters.The aim of the test was to study the distributions and functions of glutamine transporters in IEC-6 cell line.Methods:The rat intestinal epithelial cell line(IEC-6) was incubated in vitro.The mRNA expression of different glutamine transporters,protein expression of system ASCT2,and the [3H]-L-glutamine uptake were measured.Results:The mRNA of system ASCT2,SN1,ATA1,LAT1,LAT2 was expressed and the protein expression of ASCT2 was also validated in IEC-6.In Na+-containing buffer,the velocity of Na+-dependent glutamine uptake was(164.07?37.94) fmol/(mg protein?10min).In Na+-free buffer,the velocity of glutamine uptake was(58.71?10.51)fmol/(mg protein?10min).With the saturate dosage of MeAIB,the velocity of glutamine uptake was(81.02 ?19.59) fmol/(mg protein?10min).Conclusion:There may be five kinds of glutamine transporters(ASCT2,SN1,ATA1,LAT1,and LAT2) in IEC-6 cell.The Na+-dependent transporter was the major contributor(64.22%) to glutamine total uptake in IEC-6.The contributions of system A and the remainder were 50.62% and 13.60%,respectively.The Na+-independent transporter was the lesser contributor(35.78%).