Abstract：
Podocytes are sensitive to insulin, which governs the functional and structural integrity of podocytes that are essential for proper function of the glomerular filtration barrier. Lysosomes are acidic organelles that are implicated in regulation of the insulin signaling pathway. Cathepsin D (CTPD) and lysosome-associated membrane protein 1 (LAMP1) are major lysosomal proteins that reflect the functional state of lysosomes. However, the effect of insulin on lysosome activity and role of lysosomes in the regulation of insulin-dependent glucose uptake in podocytes are unknown. Our studies showed that the short-term incubation of podocytes with insulin decreased LAMP1 and CTPD mRNA levels. Insulin and bafilomycin A1 reduced both the amounts of LAMP1 and CTPD proteins and activity of CTPD, which were associated with a decrease in the fluorescence intensity of lysosomes that were labeled with LysoTracker. Bafilomycin A1 inhibited insulin-dependent endocytosis of the insulin receptor and increased the amounts of the insulin receptor and glucose transporter 4 on the cell surface of podocytes. Bafilomycin A1 also inhibited insulin-dependent glucose uptake despite an increase in the amount of glucose transporter 4 in the plasma membrane of podocytes. These results suggest that lysosomes are signaling hubs that may be involved in the coupling of insulin signaling with the regulation of glucose uptake in podocytes. The dysregulation of this mechanism can lead to the dysfunction of podocytes and development of insulin resistance.
摘要：
足细胞对胰岛素敏感,它控制足细胞的功能和结构完整性，这对于肾小球滤过屏障的正常功能至关重要。溶酶体是与胰岛素信号通路的调节有关的酸性细胞器。组织蛋白酶D（CTPD）和溶酶体相关膜蛋白1（LAMP1）是反映溶酶体功能状态的主要溶酶体蛋白。然而,胰岛素对溶酶体活性的影响以及溶酶体在足细胞胰岛素依赖性葡萄糖摄取调节中的作用尚不清楚.我们的研究表明，足细胞与胰岛素的短期孵育降低了LAMP1和CTPDmRNA水平。胰岛素和巴弗洛霉素A1降低了LAMP1和CTPD蛋白的含量和CTPD的活性，这与用LysoTracker标记的溶酶体的荧光强度降低有关。巴弗洛霉素A1抑制胰岛素受体的胰岛素依赖性内吞作用，并增加足细胞表面胰岛素受体和葡萄糖转运蛋白4的量。尽管足细胞质膜中葡萄糖转运蛋白4的量增加，巴弗洛霉素A1也抑制了胰岛素依赖性葡萄糖的摄取。这些结果表明，溶酶体是信号中枢，可能参与胰岛素信号与足细胞葡萄糖摄取调节的偶联。这种机制的失调可导致足细胞功能障碍和胰岛素抵抗的发展。
