A NOVEL MECHANISM OF REGULATION OF INOSITOL BIOSYNTHESIS IN YEAST

描述（由申请人提供）：肌醇是一种必需代谢物，在调节细胞信号通路中起着重要作用。在酵母中，肌醇影响700多个基因的转录。此外，许多肌醇磷酸和磷酸肌醇是控制基本细胞途径的信号分子。因此，肌醇稳态必须高度调节。大量研究表明，肌醇生物合成在INO 1基因的转录水平上受到控制，INO 1基因编码肌醇3-磷酸合酶（MIPS）。然而，肌醇水平的调节不能仅仅通过调节INO 1表达来解释，因为导致肌醇耗尽的几种生理条件的特征在于肌醇合成减少，尽管INO 1表达增加。事实上，初步研究表明，MIPS活性降低是由于MIPS蛋白的磷酸化，而不是由于INO 1 mRNA的降低。有趣的是，肌醇合成的抑制扰乱液泡功能和V-ATP酶活性。基于这些发现，拟议的研究将解决的假设，肌醇稳态是由磷酸化的MIPS控制，肌醇耗竭导致液泡功能和ATP酶活性的扰动。V-ATP酶是一种高度保守的泵，对于将分子转运到酸性细胞器中至关重要。在突触囊泡中，V-ATP酶活性驱动神经递质的摄取。因此，肌醇消耗药物对V-ATPase的扰动预计对神经传递具有重要意义。具体目标将解决以下问题：1）MIPS磷酸化的潜在机制是什么？2)肌醇耗竭是如何导致液泡功能紊乱的？3)什么机制控制人类细胞中的MIPS？这项研究将首次描述一种新的调节机制，控制肌醇稳态，并将这种调节与液泡功能和V-ATP酶活性联系起来。这项研究还将解决我们对肌醇合成如何在人类细胞中调节的理解中的严重差距。由于含肌醇的化合物涉及神经和精神疾病、肌病、癌症和糖尿病等多种疾病，这些研究的结果将对理解对人类健康至关重要的调节途径产生强大的影响。公共卫生相关性：这项研究将阐明一种新的控制肌醇稳态的分子机制和这种调节的细胞后果。肌醇是一种重要的代谢传感器，在调节细胞信号通路中起着重要作用。由于含肌醇的化合物涉及神经和精神疾病、肌病、癌症和糖尿病等多种疾病，这些研究的结果将对理解对人类健康至关重要的调节途径产生强大的影响。

DESCRIPTION (provided by applicant): Inositol is an essential metabolite that plays a fundamental role in regulating cellular signaling pathways. In yeast, inositol affects the transcription of over 700 genes. In addition, many inositol phosphates and phosphoinositides are signaling molecules that control essential cellular pathways. Therefore, inositol homeostasis must be highly regulated. Numerous studies have shown that inositol biosynthesis is controlled at the level of transcription of the INO1 gene, which encodes myo-inositol 3-phosphate synthase (MIPS). However, regulation of inositol levels cannot be explained solely by modulating INO1 expression, as several physiological conditions that lead to inositol depletion are characterized by decreased inositol synthesis in spite of an increase in INO1 expression. In fact, preliminary studies indicate that decreased MIPS activity results from phosphorylation of the MIPS protein, not from decreased INO1 mRNA. Interestingly, inhibition of inositol synthesis perturbs vacuole function and V-ATPase activity. Based on these findings, the proposed study will address the hypothesis that inositol homeostasis is controlled by the phosphorylation of MIPS, and that inositol depletion leads to perturbation of vacuolar function and ATPase activity. The V-ATPase is a highly conserved pump that is essential for the transport of molecules into acidic organelles. In synaptic vesicles, V-ATPase activity drives the uptake of neurotransmitters. Therefore, perturbation of the V-ATPase by inositol depleting drugs is expected to have important implications for neurotransmission. The specific aims will address the following questions: 1) What is the mechanism underlying the phosphorylation of MIPS? 2) How does inositol depletion lead to perturbation of vacuolar function? 3) What mechanisms control MIPS in human cells? This study will characterize for the first time a novel regulatory mechanism that controls inositol homeostasis and that links this regulation to vacuolar function and V-ATPase activity. This study will also address the serious gap in our understanding of how inositol synthesis is regulated in human cells. Because inositol-containing compounds are involved in disorders as diverse as neurological and psychiatric illnesses, myopathies, cancer, and diabetes, the outcome of these studies will have a powerful impact on understanding regulatory pathways crucial to human health. PUBLIC HEALTH RELEVANCE: The proposed study will elucidate a novel molecular mechanism of control of inositol homeostasis and the cellular consequences of this regulation. Inositol is an essential metabolic sensor that plays a fundamental role in regulating cellular signaling pathways. Because inositol-containing compounds are involved in disorders as diverse as neurological and psychiatric illnesses, myopathies, cancer, and diabetes, the outcome of these studies will have a powerful impact on understanding regulatory pathways crucial to human health.