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

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 <i>Drosophila</i>, controls expression of vacuolar-type H⁺-ATPase pump (V-ATPase) subunits. Remarkably, we also find that expression of <i>Vha16-1</i> and <i>Vha13</i>, encoding 2 key components of V-ATPase, is patterned in the wing imaginal disc. In particular, <i>Vha16-1</i> 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 <i>Drosophila</i>, in human breast epithelial cells we observe that impairment of the <i>Vha16-1</i> human ortholog <i>ATP6V0C</i> 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，转录因子EB（TFEB，transcription factor EB）与小眼症相关转录因子（MITF，microphthalmia-associated transcription factor）家族的碱性螺旋-环-螺旋（basic Helix-Loop-Helix，bHLH）转录因子，可同时调控溶酶体功能与器官发育。然而，目前尚不清楚这两类生物学过程是否存在关联。本研究证实，果蝇（Drosophila）中唯一的TFEB与MITF同源物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，本研究还发现，编码V-ATPase两个关键组分的基因Vha16-1与Vha13，在翅成虫盘（wing imaginal disc）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神经前体区域分化进程高度同步。这些将发育为成虫感觉器官的神经前体区域，具有独特的内溶酶体区室与Notch（N）定位特征。在体调控果蝇翅成虫盘中Mitf的活性，可改变内溶酶体功能并扰乱神经前体模式的形成。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均发生改变；而TFEB敲低则会降低配体非依赖型Notch信号活性。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作用。