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Proc Natl Acad Sci U S A. 2014 Sep 9;111(36):13087-92. doi: 10.1073/pnas.1407004111. Epub 2014 Aug 25.

The Two-pore channel (TPC) interactome unmasks isoform-specific roles for TPCs in endolysosomal morphology and cell pigmentation.

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Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455;
Department of Cell and Developmental Biology, University College London, London WC1E 6BT, United Kingdom; and.
Departments of Anatomy, Cell Biology, and Pharmacology and the Center for Substance Abuse, Temple University School of Medicine, Philadelphia, PA 19140.
Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455;


The two-pore channels (TPC1 and TPC2) belong to an ancient family of intracellular ion channels expressed in the endolysosomal system. Little is known about how regulatory inputs converge to modulate TPC activity, and proposed activation mechanisms are controversial. Here, we compiled a proteomic characterization of the human TPC interactome, which revealed that TPCs complex with many proteins involved in Ca(2+) homeostasis, trafficking, and membrane organization. Among these interactors, TPCs were resolved to scaffold Rab GTPases and regulate endomembrane dynamics in an isoform-specific manner. TPC2, but not TPC1, caused a proliferation of endolysosomal structures, dysregulating intracellular trafficking, and cellular pigmentation. These outcomes required both TPC2 and Rab activity, as well as their interactivity, because TPC2 mutants that were inactive, or rerouted away from their endogenous expression locale, or deficient in Rab binding, failed to replicate these outcomes. Nicotinic acid adenine dinucleotide phosphate (NAADP)-evoked Ca(2+) release was also impaired using either a Rab binding-defective TPC2 mutant or a Rab inhibitor. These data suggest a fundamental role for the ancient TPC complex in trafficking that holds relevance for lysosomal proliferative scenarios observed in disease.


Ca2+ signaling; Xenopus; lysosome

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