Roni Levin-Konigsberg, Koushambi Mitra, Kaitlyn Spees, AkshatKumar Nigam, Katherine Liu, Camille Januel, Pravin Hivare, Sophia M. Arana, Laura M. Prolo, Anshul Kundaje, Manuel D. Leonetti, Yamuna Krishnan, Michael C. Bassik
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An SLC12A9-dependent ion transport mechanism maintains lysosomal osmolarity
Ammonia is a ubiquitous, toxic by-product of cell metabolism. Its high membrane permeability and proton affinity cause ammonia to accumulate inside acidic lysosomes in its poorly membrane-permeant form: ammonium (NH4+). Ammonium buildup compromises lysosomal function, suggesting the existence of mechanisms that protect cells from ammonium toxicity. Here, we identified SLC12A9 as a lysosomal-resident protein that preserves organelle homeostasis by controlling ammonium and chloride levels. SLC12A9 knockout (KO) cells showed grossly enlarged lysosomes and elevated ammonium content. These phenotypes were reversed upon removal of the metabolic source of ammonium or dissipation of the lysosomal pH gradient. Lysosomal chloride increased in SLC12A9 KO cells, and chloride binding by SLC12A9 was required for ammonium transport. Our data indicate that SLC12A9 function is central for the handling of lysosomal ammonium and chloride, an unappreciated, fundamental mechanism of lysosomal physiology that may have special relevance in tissues with elevated ammonia, such as tumors.
期刊介绍:
Developmental Cell, established in 2001, is a comprehensive journal that explores a wide range of topics in cell and developmental biology. Our publication encompasses work across various disciplines within biology, with a particular emphasis on investigating the intersections between cell biology, developmental biology, and other related fields. Our primary objective is to present research conducted through a cell biological perspective, addressing the essential mechanisms governing cell function, cellular interactions, and responses to the environment. Moreover, we focus on understanding the collective behavior of cells, culminating in the formation of tissues, organs, and whole organisms, while also investigating the consequences of any malfunctions in these intricate processes.