title: Controlled and stochastic retention concentrates dynein at microtubule ends to keep endosomes on track.
abstract: Bidirectional transport of early endosomes (EEs) involves microtubules (MTs) and associated motors. In fungi, the dynein/dynactin motor complex concentrates in a comet-like accumulation at MT plus-ends to receive kinesin-3-delivered EEs for retrograde transport. Here, we analyse the loading of endosomes onto dynein by combining live imaging of photoactivated endosomes and fluorescent dynein with mathematical modelling. Using nuclear pores as an internal calibration standard, we show that the dynein comet consists of ∼55 dynein motors. About half of the motors are slowly turned over (T(1/2): ∼98 s) and they are kept at the plus-ends by an active retention mechanism involving an interaction between dynactin and EB1. The other half is more dynamic (T(1/2): ∼10 s) and mathematical modelling suggests that they concentrate at MT ends because of stochastic motor behaviour. When the active retention is impaired by inhibitory peptides, dynein numbers in the comet are reduced to half and ∼10% of the EEs fall off the MT plus-ends. Thus, a combination of stochastic accumulation and active retention forms the dynein comet to ensure capturing of arriving organelles by retrograde motors.
authors.affiliation: School of Biosciences, University of Exeter, Exeter, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Schuster
authors.forename: Sreedhar
authors.initials: S
authors.lastname: Kilaru
authors.forename: Peter
authors.initials: P
authors.lastname: Ashwin
authors.forename: Congping
authors.initials: C
authors.lastname: Lin
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Severs
authors.forename: Gero
authors.initials: G
authors.lastname: Steinberg
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport / Q000502:physiology; D004398:Dyneins / Q000032:analysis / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D008954:Models, Biological; D008962:Models, Theoretical; D030781:Organisms, Genetically Modified; D009994:Osmolar Concentration; D011485:Protein Binding / Q000502:physiology; D055503:Protein Multimerization / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013269:Stochastic Processes; D014588:Ustilago / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D004398:Dyneins