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Lipid storage disorders block lysosomal trafficking by inhibiting a TRP channel and lysosomal calcium release
Author(s): Dongbiao Shen, Xiang Wang, Xinran Li, Xiaoli Zhang, Zepeng Yao, Shannon Dibble, Xian-ping Dong, Ting Yu, Andrew P. Lieberman, Hollis D. Showalter, Haoxing Xu
Lysosomal lipid accumulation, defects in membrane trafficking and altered Ca2+ homoeostasis are common features in many lysosomal storage diseases. Mucolipin transient receptor potential channel 1 (TRPML1) is the principle Ca2+ channel in the lysosome. Here we show that TRPML1-mediated lysosomal Ca2+ release, measured using a genetically encoded Ca2+ indicator (GCaMP3) attached directly to TRPML1 and elicited by a potent membrane-permeable synthetic agonist, is dramatically reduced in Niemann-Pick (NP) disease cells. Sphingomyelins (SMs) are plasma membrane lipids that undergo sphingomyelinase (SMase)-mediated hydrolysis in the lysosomes of normal cells, but accumulate distinctively in lysosomes of NP cells. Patch-clamp analyses revealed that TRPML1 channel activity is inhibited by SMs, but potentiated by SMases. In NP-type C cells, increasing TRPML1's expression or activity was sufficient to correct the trafficking defects and reduce lysosome storage and cholesterol accumulation. We propose that abnormal accumulation of luminal lipids causes secondary lysosome storage by blocking TRPML1- and Ca2+-dependent lysosomal trafficking.
This paper was featured in the U-M News Service article "U-M biologists find potential drug that speeds cellular recycling."
Name of Periodical: Nature Communications
Year of Publication: 2012