Abstract
The cytoplasmic dynein-1 (dynein) motor plays a central role in microtubule organisation and cargo transport. These functions are spatially regulated by association of dynein and its accessory complex dynactin with dynamic microtubule plus ends. Here, we elucidate in vitro the roles of dynactin, end-binding protein-1 (EB1) and Lissencephaly-1 (LIS1) in the interaction of end tracking and minus end-directed human dynein complexes with these sites. LIS1 promotes dynactin-dependent tracking of dynein on both growing and shrinking plus ends. LIS1 also increases the frequency and velocity of processive dynein movements that are activated by complex formation with dynactin and a cargo adaptor. This stimulatory effect of LIS1 contrasts sharply with its documented ability to inhibit the activity of isolated dyneins. Collectively, our findings shed light on how mammalian dynein complexes associate with dynamic microtubules and help clarify how LIS1 promotes the plus-end localisation and cargo transport functions of dynein in vivo.
Highlights
Cytoplasmic dynein-1 is a 1.4 MDa, multi-subunit motor complex that is responsible for the vast majority of cargo transport towards the minus ends of microtubules in eukaryotic cells
We developed assay conditions that are permissive for the interaction of non-processive and minus end-directed mammalian dynein complexes with microtubules exhibiting dynamic instability (Figure 1; Materials and methods)
To attempt to reconcile our findings with those of the previous studies, we investigated in more detail the influence of LIS1 on the interaction of single human dynein complexes with the microtubule lattice in the absence of end-binding protein-1 (EB1) and dynactin
Summary
Cytoplasmic dynein-1 (hereafter referred to as dynein) is a 1.4 MDa, multi-subunit motor complex that is responsible for the vast majority of cargo transport towards the minus ends of microtubules in eukaryotic cells. In addition to its function on motile cargoes, dynein plays important roles in organising microtubules in mitotic and interphase cells Dynein – like all cytoskeletal motors – functions within cells on a dynamic network of tracks. Whereas the microtubule minus ends are often stabilised in vivo, the plus ends alternate between phases of polymerisation (‘growth’) and depolymerisation (‘shrinkage’)—a process known as dynamic instability. Microtubule plus ends are stabilised during growth by a cap of tubulin-GTP, with depolymerisation triggered when the GTP bound to b-tubulin at the microtubule tip is hydrolysed (Carlier, 1982; Mitchison and Kirschner, 1984). The dynamic nature of microtubules facilitates exploration of the cytoplasm in order to establish and remodel contacts with cellular components (Kirschner and Mitchison, 1986; Lomakin et al, 2009; Mimori-Kiyosue and Tsukita, 2003; Tamura and Draviam, 2012)
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