Non-genomic mechanisms stabilizing the abundance of SNAT2 a nutrient transceptor protein in response to diverse catabolic signals

稳定营养转运蛋白 SNAT2 丰度的非基因组机制，以响应不同的分解代谢信号

• 批准号: BB/I007261/1
• 负责人: Hari Hundal
• 金额: $ 41.08万
• 依托单位: University of Dundee
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FI007261%2F1
• 关键词: Non; genomic; mechanisms; stabilizing; abundance

Cells grow in response to the availability of nutrients including amino acids, which are required as precursors of new protein and also used as a metabolic fuel. This fundamental growth response is most obvious in primitive organisms such as yeast, but the systems underlying the response are retained in mammalian cells and are increasingly recognised as a vital mechanism for control of cell function in the human body. Unfortunately, the sensitivity of this response diminishes as we age and contributes to a gradual loss in muscle mass (known as 'age-related sarcopenia'), which limits mobility and hence overall health and quality of life. Important components of the nutrient-response system are biological sensors of nutrient availability, one of which (known as SNAT2) we are studying to see whether it can be manipulated so as to counteract the processes underlying development of sarcopenia. SNAT2 is a protein in the surface membrane of most types of human cell which, we have discovered, acts as a sensor (or receptor) for external amino acids in tandem with a well-known role as a transporter of these amino acids into the cell for protein synthesis (and hence cell growth). The double-life of this transporter / receptor protein has led to it being christened the SNAT2 'transceptor'. In common with other proteins, SNAT2 undergoes a continual cycle of synthesis and degradation, a turnover which ensures that SNAT2 is maintained at appropriate levels and that individual SNAT2 molecules are replaced regularly as part of cellular 'housekeeping'. The amount of SNAT2 protein in cells is highly-regulated and is increased when cells are stressed either by amino acid starvation or steroid (dexamethasone) treatment. This up-regulation may be an important part of the cellular response to stress and should help modulate the sensitivity of the SNAT2 transceptor system under different circumstances. Our recent research has shown that SNAT2 turns over relatively quickly and, at least in skeletal muscle cells, its abundance is regulated largely by reducing the rate at which the protein is degraded. SNAT2 proteins are earmarked for degradation by the sequential attachment of a chain of ubiquitin molecules, identifying them as targets for the proteasome, a major component of the biochemical machinery which breaks down cellular proteins. We have preliminary evidence that this ubiquitin-targeting system for SNAT2 is compromised during various stresses, thus stabilizing SNAT2 proteins by reducing their rate of degradation. Because new SNAT2 proteins are continually being synthesized, the net effect is to increase their overall abundance and hence their capacity to signal for cell growth. This project aims to work out how SNAT2 proteins evade degradation during cellular stresses, how much this helps to minimize stress effects (e.g. by maintaining activity of certain growth pathways) and whether the mechanisms involved may be targeted in order to promote cell growth (e.g. to counteract age-related muscle wasting) or, if an inhibitor is developed, to reduce cell growth (e.g. in cancer chemotherapy). Targeted therapies of this type might include specific modifications to protein nutrition as well as drugs which affect activity of SNAT2 or its degradation mechanism, both of which might be of particular benefit to the elderly population in terms improving health and quality of life, as well as reducing overall healthcare costs. There may also be additional spin-off applications and benefits to this research related to the ongoing interest in the ubiquitin - proteasome system as a regulator of several other genes of therapeutic interest (e.g. ENac, a target for treatment of cystic fibrosis).

细胞生长是对营养素的可用性做出反应，包括氨基酸，这些营养素是新蛋白质的前体，也被用作代谢燃料。这种基本的生长反应在原始生物如酵母中最为明显，但反应背后的系统保留在哺乳动物细胞中，并且越来越多地被认为是控制人体细胞功能的重要机制。不幸的是，这种反应的敏感性随着年龄的增长而降低，并导致肌肉质量逐渐减少（称为“年龄相关性肌肉减少症”），这限制了活动性，从而限制了整体健康和生活质量。营养反应系统的重要组成部分是营养可用性的生物传感器，我们正在研究其中之一（称为SNAT 2），看看它是否可以被操纵，以抵消肌肉减少症的潜在发展过程。SNAT 2是大多数类型的人类细胞的表面膜中的蛋白质，我们已经发现，它作为外部氨基酸的传感器（或受体），与众所周知的作为这些氨基酸进入细胞用于蛋白质合成（并因此细胞生长）的转运蛋白的作用串联。这种转运蛋白/受体蛋白的双重生命导致它被命名为SNAT 2“受体”。与其他蛋白质一样，SNAT 2经历了连续的合成和降解循环，这种周转确保SNAT 2维持在适当的水平，并且作为细胞“管家”的一部分，单个SNAT 2分子定期更换。细胞中SNAT 2蛋白的量是高度调节的，并且当细胞通过氨基酸饥饿或类固醇（地塞米松）处理应激时增加。这种上调可能是细胞对压力反应的重要组成部分，并应有助于调节SNAT 2受体系统在不同情况下的敏感性。我们最近的研究表明，SNAT 2转换相对较快，至少在骨骼肌细胞中，其丰度主要通过降低蛋白质降解速率来调节。SNAT 2蛋白被指定为通过顺序连接泛素分子链进行降解，将其鉴定为蛋白酶体的靶标，蛋白酶体是分解细胞蛋白的生化机制的主要组分。我们有初步的证据表明，这种针对SNAT 2的泛素靶向系统在各种应激过程中受到损害，从而通过降低其降解速率来稳定SNAT 2蛋白。由于新的SNAT 2蛋白不断合成，净效应是增加它们的总体丰度，从而增加它们发出细胞生长信号的能力。该项目旨在弄清楚SNAT 2蛋白如何在细胞应激期间逃避降解，这在多大程度上有助于最大限度地减少应激影响（例如，通过维持某些生长途径的活性），以及是否可以针对所涉及的机制以促进细胞生长（例如，对抗与年龄相关的肌肉萎缩），或者，如果开发出抑制剂，则减少细胞生长（例如，在癌症化疗中）。这种类型的靶向治疗可能包括对蛋白质营养的特定修饰以及影响SNAT 2活性或其降解机制的药物，这两者在改善健康和生活质量以及降低整体医疗保健成本方面可能对老年人特别有益。这项研究还可能有额外的副产品应用和益处，这些应用和益处与泛素-蛋白酶体系统作为其他几种治疗相关基因（例如，ENac，囊性纤维化治疗的靶点）的调节剂的持续兴趣有关。

项目成果

SNAT2 transceptor signalling via mTOR: a role in cell growth and proliferation?

• DOI: 10.2741/e332
• 发表时间: 2011
• 期刊: Frontiers in bioscience
• 作者: Jorge Pinilla;J. Aledo;Emma Cwiklinski;R. Hyde;P. Taylor;H. Hundal

GSK3-mediated raptor phosphorylation supports amino-acid-dependent mTORC1-directed signalling.

GSK3介导的Raptor磷酸化支持氨基酸依赖性MTORC1定向信号传导。

• DOI: 10.1042/bj20150404
• 发表时间: 2015-09-01
• 期刊: The Biochemical journal
• 作者: Stretton C;Hoffmann TM;Munson MJ;Prescott A;Taylor PM;Ganley IG;Hundal HS
• 通讯作者: Hundal HS

Is REDD1 a Metabolic Éminence Grise?

• DOI: 10.1016/j.tem.2016.08.005
• 发表时间: 2016-12
• 期刊: TRENDS IN ENDOCRINOLOGY AND METABOLISM
• 影响因子: 10.9
• 作者: Lipina, Christopher;Hundal, Harinder S.
• 通讯作者: Hundal, Harinder S.

CDK7 is a component of the integrated stress response regulating SNAT2 (SLC38A2)/System A adaptation in response to cellular amino acid deprivation.

CDK7 是调节 SNAT2 (SLC38A2)/系统 A 适应以响应细胞氨基酸剥夺的综合应激反应的一个组成部分。

• DOI: 10.1016/j.bbamcr.2019.03.002
• 发表时间: 2019
• 期刊: Biochimica et biophysica acta. Molecular cell research
• 作者: Stretton C

The catalytic subunit of the system L1 amino acid transporter (slc7a5) facilitates nutrient signalling in mouse skeletal muscle.

• DOI: 10.1371/journal.pone.0089547
• 发表时间: 2014
• 期刊: PloS one
• 影响因子: 3.7
• 作者: Poncet N;Mitchell FE;Ibrahim AF;McGuire VA;English G;Arthur JS;Shi YB;Taylor PM
• 通讯作者: Taylor PM