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A septin GTPase scaffold of dynein-dynactin motors triggers retrograde lysosome transport.

The Journal of cell biology (2021-01-09)
Ilona A Kesisova, Benjamin P Robinson, Elias T Spiliotis
ABSTRACT

The metabolic and signaling functions of lysosomes depend on their intracellular positioning and trafficking, but the underlying mechanisms are little understood. Here, we have discovered a novel septin GTPase-based mechanism for retrograde lysosome transport. We found that septin 9 (SEPT9) associates with lysosomes, promoting the perinuclear localization of lysosomes in a Rab7-independent manner. SEPT9 targeting to mitochondria and peroxisomes is sufficient to recruit dynein and cause perinuclear clustering. We show that SEPT9 interacts with both dynein and dynactin through its GTPase domain and N-terminal extension, respectively. Strikingly, SEPT9 associates preferentially with the dynein intermediate chain (DIC) in its GDP-bound state, which favors dimerization and assembly into septin multimers. In response to oxidative cell stress induced by arsenite, SEPT9 localization to lysosomes is enhanced, promoting the perinuclear clustering of lysosomes. We posit that septins function as GDP-activated scaffolds for the cooperative assembly of dynein-dynactin, providing an alternative mechanism of retrograde lysosome transport at steady state and during cellular adaptation to stress.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
MISSION® esiRNA, targeting human SEPT9
Sigma-Aldrich
Nocodazole, ≥99% (TLC), powder
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Magnesium acetate solution, BioUltra, for molecular biology, ~1 M in H2O
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Triton X-100, laboratory grade
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DAPI, for nucleic acid staining
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Anti-LAMTOR4 antibody produced in rabbit, affinity isolated antibody, buffered aqueous glycerol solution