Control of lysosomal biogenesis and Notch-dependent tissue patterning by components of the TFEB-V-ATPase axis in Drosophila melanogaster

In vertebrates, TFEB (transcription factor EB) and MITF (microphthalmia-associated transcription factor) family of basic Helix-Loop-Helix (bHLH) transcription factors regulates both lysosomal function and organ development. However, it is not clear whether these 2 processes are interconnected. Here, we show that Mitf, the single TFEB and MITF ortholog in Drosophila, controls expression of vacuolar-type H+-ATPase pump (V-ATPase) subunits. Remarkably, we also find that expression of Vha16-1 and Vha13, encoding 2 key components of V-ATPase, is patterned in the wing imaginal disc. In particular, Vha16-1 expression follows differentiation of proneural regions of the disc. These regions, which will form sensory organs in the adult, appear to possess a distinctive endolysosomal compartment and Notch (N) localization. Modulation of Mitf activity in the disc in vivo alters endolysosomal function and disrupts proneural patterning. Similar to our findings in Drosophila, in human breast epithelial cells we observe that impairment of the Vha16-1 human ortholog ATP6V0C changes the size and function of the endolysosomal compartment and that depletion of TFEB reduces ligand-independent N signaling activity. Our data suggest that lysosomal-associated functions regulated by the TFEB-V-ATPase axis might play a conserved role in shaping cell fate.

在脊椎动物中，碱性螺旋-环-螺旋（basic Helix-Loop-Helix，bHLH）转录因子家族的转录因子EB（transcription factor EB，TFEB）与小眼相关转录因子（microphthalmia-associated transcription factor，MITF），可同时调控溶酶体功能与器官发育。然而目前尚不明确这两类生物学过程是否存在关联。本研究中，我们发现果蝇体内唯一的TFEB与MITF同源基因Mitf，可调控液泡型H+-ATP酶泵（vacuolar-type H+-ATPase pump，V-ATPase）亚基的表达。值得注意的是，我们还发现编码V-ATPase两个关键亚基的Vha16-1与Vha13，在翅成虫盘中呈现特异性表达模式。具体而言，Vha16-1的表达模式与该成虫盘的前体神经区域分化进程高度契合。这些未来将发育为成体感觉器官的区域，具有独特的内溶酶体区室结构与Notch受体（Notch，N）定位特征。在活体成虫盘中调控Mitf的活性，可改变内溶酶体功能并扰乱前体神经区域的表达模式。与果蝇中的研究结果一致，在人类乳腺上皮细胞中我们观察到：Vha16-1的人类同源基因ATP6V0C功能受损时，内溶酶体区室的大小与功能会发生改变；而TFEB的敲低则会降低配体非依赖型N信号通路的活性。本研究数据表明，由TFEB-V-ATPase轴调控的溶酶体相关功能，可能在细胞命运塑造过程中发挥保守性作用。