Cao Qi, Yang Yiming, Zhong Xi Zoë, Dong Xian-Ping
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
J Biol Chem. 2017 May 19;292(20):8424-8435. doi: 10.1074/jbc.M116.772160. Epub 2017 Mar 30.
Intracellular lysosomal membrane trafficking, including fusion and fission, is crucial for cellular homeostasis and normal cell function. Both fusion and fission of lysosomal membrane are accompanied by lysosomal Ca release. We recently have demonstrated that the lysosomal Ca release channel P2X4 regulates lysosome fusion through a calmodulin (CaM)-dependent mechanism. However, the molecular mechanism underlying lysosome fission remains uncertain. In this study, we report that enlarged lysosomes/vacuoles induced by either vacuolin-1 or P2X4 activation are suppressed by up-regulating the lysosomal Ca release channel transient receptor potential mucolipin 1 (TRPML1) but not the lysosomal Na release channel two-pore channel 2 (TPC2). Activation of TRPML1 facilitated the recovery of enlarged lysosomes/vacuoles. Moreover, the effects of TRPML1 on lysosome/vacuole size regulation were eliminated by Ca chelation, suggesting a requirement for TRPML1-mediated Ca release. We further demonstrate that the prototypical Ca sensor CaM is required for the regulation of lysosome/vacuole size by TRPML1, suggesting that TRPML1 may promote lysosome fission by activating CaM. Given that lysosome fission is implicated in both lysosome biogenesis and reformation, our findings suggest that TRPML1 may function as a key lysosomal Ca channel controlling both lysosome biogenesis and reformation.
细胞内溶酶体膜运输，包括融合和裂变，对细胞内稳态和正常细胞功能至关重要。溶酶体膜的融合和裂变均伴随着溶酶体钙释放。我们最近证明，溶酶体钙释放通道P2X4通过钙调蛋白（CaM）依赖性机制调节溶酶体融合。然而，溶酶体裂变的分子机制仍不确定。在本研究中，我们报告称，由空泡菌素-1或P2X4激活诱导的溶酶体/液泡增大可通过上调溶酶体钙释放通道瞬时受体电位黏脂质1（TRPML1）而不是溶酶体钠释放通道双孔通道2（TPC2）来抑制。TRPML1的激活促进了增大的溶酶体/液泡的恢复。此外，钙螯合消除了TRPML1对溶酶体/液泡大小调节的影响，表明TRPML1介导的钙释放是必需的。我们进一步证明，典型的钙传感器CaM是TRPML1调节溶酶体/液泡大小所必需的，这表明TRPML1可能通过激活CaM促进溶酶体裂变。鉴于溶酶体裂变与溶酶体生物发生和重塑均有关，我们的研究结果表明，TRPML1可能作为控制溶酶体生物发生和重塑的关键溶酶体钙通道发挥作用。
