Rab7 and Arl8 GTPases are necessary for lysosome tubulation in macrophages.
Lysosomes provide a niche for molecular digestion and are a convergence point for endocytic trafficking, phagosome maturation and autophagy. Typically, lysosomes are small, globular organelles that appear punctate under the fluorescence microscope. However, activating agents like phorbol esters transform macrophage lysosomes into tubular lysosomes (TLs), which have been implicated in retention of pinocytic uptake and phagosome maturation. Moreover, dendritic cells exposed to lipopolysaccharides (LPSs) convert their punctate class II major histocompatibility complex compartment, a lysosome-related organelle, into a tubular network that is thought to be involved in antigen presentation. Other than a requirement for microtubules and kinesin, little is known about the molecular mechanisms that drive lysosome tubulation. Here, we show that macrophage cell lines readily form TLs after LPS exposure, with a requirement for the Rab7 GTPase and its effectors RILP (Rab7-interacting lysosomal protein) and FYCO1 (coiled-coil domain-containing protein 1), which respectively modulate the dynein and kinesin microtubule motor proteins. We also show that Arl8B, a recently identified lysosomal GTPase, and its effector SKIP, are also important for TL biogenesis. Finally, we reveal that TLs are significantly more motile than punctate lysosomes within the same LPS-treated cells. Therefore, we identify the first molecular regulators of lysosome tubulation and we show that TLs represent a more dynamic lysosome population.
Molecular Science Program and the Department of Chemistry and Biology, Ryerson University, Toronto, ON, M5B 2K3, Canada.
Amra
A
Mrakovic
Jason G
JG
Kay
Wendy
W
Furuya
John H
JH
Brumell
Roberto J
RJ
Botelho
D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D008070:Lipopolysaccharides / Q000494:pharmacology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D051379:Mice; D053140:Organelle Shape; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000090802:rab7 GTP-Binding Proteins
D048868:Adaptor Proteins, Signal Transducing; C581820:Arl8B protein, mouse; D002352:Carrier Proteins; D008070:Lipopolysaccharides; C498920:Rilp protein, mouse; D014157:Transcription Factors; D000090802:rab7 GTP-Binding Proteins; C000716465:rab7 GTP-binding proteins, mouse; C531212:Pps protein, mouse; D010744:Phosphoric Monoester Hydrolases; D020727:ADP-Ribosylation Factors; D020691:rab GTP-Binding Proteins