Regulation of insulin sensitivity by the Src family non-receptor tyrosine kinase,

描述(申请人提供)：最近，我们实验室已经开始研究胰岛素受体信号与非受体酪氨酸激酶Src、Lyn和Fyn之间的串扰。我们发现，Fyn基因缺失的小鼠表现出显著的减脂作用，增加了脂肪酸氧化，增强了儿茶酚胺刺激的脂解作用，并改善了胰岛素敏感性。令人惊讶的是，这些小鼠在高脂肪饮食下也增加了相当大的体重和脂肪组织质量，但即使与它们瘦弱的野生型对照组相比，尽管存在明显的血脂异常，仍保持高度的葡萄糖耐量。骨骼肌和脂肪组织氧化的增强伴随着苏氨酸172亚单位上AMPK磷酸化的增加(激活部位磷酸化)和其负调控部位乙酰辅酶A羧基酶的磷酸化增加。脂解率的增加是由于Perilipin的磷酸化和激素敏感脂肪酶激活部位的磷酸化增加所致。尽管传统的Fyn基因缺失小鼠在能量利用和胰岛素敏感性方面表现出显著的改善，但这些数据并没有说明Fyn功能的丧失是通过信号的急性变化还是通过发育适应来表现的。此外，有三种Fyn的剪接变体似乎具有不同的功能和组织特异性分布模式。因此，对常规FYN缺失小鼠的分析不能解决这些问题。因此，我们建议在这个R21应用程序中，通过产生同型组织特异性Fyn转基因表达小鼠和可诱导的组织特异性Fyn基因敲除小鼠来确定这些影响是否以细胞自主或非自主的方式发生。然后，我们建议使用敲入技术在骨骼肌和脂肪组织中产生异构体特异的Fyn表达。这些动物将通过详细分析与全身整合系统生理学相关的调节代谢信号的分子信号通路来进行检查。糖尿病、肥胖和胰岛素抵抗状态都可以被描述为身体对能量消耗和输出的差异进行调整的能力缺陷。我们发现，Fyn酶只在禁食状态下调节脂肪酸氧化，而在进食状态下不调节。这意味着有可能调节FYN的活性，从而增加脂肪酸氧化和能量消耗(例如：减少肥胖)。因此，本项目致力于开发和表征小鼠模型，以直接测试Fyn功能改变的综合生理后果。

DESCRIPTION (provided by applicant): Recently, our laboratory has begun to investigate the cross talk between insulin receptor signaling with that of the non-receptor tyrosine kinases Src, Lyn and Fyn. We have found that Fyn null mice display markedly reduced adiposity, increased fatty acid oxidation, enhanced cateholamine-stimulated lipolysis and improved insulin sensitivity. Surprisingly, this mice also gain substantial weight and adipose tissue mass on a high fat diet, yet remain highly glucose tolerant even compared to their lean wild type controls despite marked dyslipidemia. The enhancement of skeletal muscle and adipose tissue oxidation occurred concomitant with increase AMPK phosphorylation on a subunit threonine 172 (activation site phosphorylation) and with increased acetylCoA carboxylase phosphorylation on its negative regulatory site. The increased rate of lipolysis resulted from increased phosphorylation of perilipin and activation site phosphorylation of hormone sensitive lipase. Although the conventional Fyn null mice display a remarkable improvement in energy utilization and insulin sensitivity, these data do not address whether the loss of Fyn function manifests through acute alterations in signaling or through developmental adaptation. Moreover, there are three splice variants of Fyn that appear to have distinct functional and tissue-specific distribution patterns. Thus, the analysis of the conventional Fyn null mice cannot address these issues. We therefore propose in this R21 application to determine whether these effects occur in a cell autonomous versus non-autonomous manner by generating isoform tissue-specific Fyn transgenic expressing mice and inducible tissue-specific Fyn knockout mice. We then propose to use knock-in technology to generate isoform specific Fyn expression in skeletal muscle and adipose tissue. These animals will be examined by detailed analysis of the molecular signaling pathways regulating metabolic signaling in relationship to whole body integrative system physiology. Diabetes, obesity and insulin resistant states can all be characterized as defects in the body's ability to adjust for differences in energy consumption and output. We have found that the enzyme Fyn regulates fatty acid oxidation only in the fasted state but not in the fed state. This means that it may be possible to modulate Fyn activity and thereby increase fatty acid oxidation and energy expenditure (e.g.: decrease obesity). Thus, this project is focused on developing and characterizing mouse models to directly test the integrative physiologic consequences of altered Fyn function.