LIS1 regulates cargo-adapter–mediated activation of dynein by overcoming its autoinhibition in vivo

Abstract

Deficiency of the LIS1 protein causes lissencephaly, a brain developmental disorder. Although LIS1 binds the microtubule motor cytoplasmic dynein and has been linked to dynein function in many experimental systems, its mechanism of action remains unclear. Here, we revealed its function in cargo-adapter–mediated dynein activation in the model organism Aspergillus nidulans. Specifically, we found that overexpressed cargo adapter HookA (Hook in A. nidulans) missing its cargo-binding domain (ΔC-HookA) causes dynein and its regulator dynactin to relocate from the microtubule plus ends to the minus ends, and this relocation requires LIS1 and its binding protein, NudE. Astonishingly, the requirement for LIS1 or NudE can be bypassed to a significant extent by mutations that prohibit dynein from forming an autoinhibited conformation in which the motor domains of the dynein dimer are held close together. Our results suggest a novel mechanism of LIS1 action that promotes the switch of dynein from the autoinhibited state to an open state to facilitate dynein activation.

The regulatory function of the AAA4 ATPase domain of cytoplasmic dynein

“…The cytoplasmic dynein motor complex (referred to here as dynein) is an intricate and ubiquitous biological nanomachine that performs most minus-end directed movement along cellular microtubules (MTs). Through its interaction with cofactors such as dynactin and lissencephaly-1 (Lis1), dynein performs a vast array of functions including intracellular transport of organelles and signaling complexes [1][2][3][4][5][6] , nuclear transport during neuronal migration [7][8][9] , regulation of mitotic spindle length and positioning, and removal of checkpoint proteins from the kinetochore during cell division [10][11][12] . Thus, it is not surprising that dynein dysfunction has been linked to a growing number of human diseases termed "dyneinopathies" [13][14][15] including malformation of cortical development (MCD) [16][17][18][19][20] , spinal muscular atrophy (SMA) 21,22 , SMA with lower extremity predominance (SMALED) [23][24][25][26] , and others 18,19,27,[28][29][30][31] .…”

Cargo-Mediated Activation of Cytoplasmic Dynein in vivo

“…In wild-type cells, dynein is accumulated at the microtubule plus ends, and this accumulation is represented by the comet-like structures formed by GFP-labeled dynein near the hyphal tip (Xiang et al, 2000;Han et al, 2001). Dynein activation, as judged by dynein relocation from the microtubule plus ends at hyphal tip (yellow arrowhead) to the minus ends at septum (Zhang Y. et al, 2017) (brown arrow), is driven by the dynein-dynactin-binding portion of the cargo adapter HookA, C-HookA, overexpressed under the gpdA promoter (gpdA-C-hookA-S, note that "S" indicates S-tag, an affinity tag for biochemical studies) (Qiu et al, 2019). In the nudF6 mutant, a NudF/LIS1 loss-of-function mutant, dynein is retained at the microtubule plus ends.…”

“…Bars, 5 µm. These images have been published previously in the Journal of Cell Biology (Qiu et al, 2019).…”

“…In A. nidulans and U. maydis, the microtubule plus end-localized dynein-dynactin interact with early endosomes on which the activating cargo adapter HookA or Hok1 is bound (Bielska et al, 2014b;Zhang et al, 2014). In A. nidulans, overexpression of the cytosolic C-HookA drives dynein departure from the microtubule plus ends and causes dynein to accumulate at the minus ends (Qiu et al, 2019; Figure 2). This supports not only the idea of cargo adapter-mediated dynein activation emerged from in vitro studies (McKenney et al, 2014;Schlager et al, 2014) but also the postulation that the plus-end dynein is activated by its early endosome cargo (Lenz et al, 2006).…”

“…Beside dynactin and cargo adapters, another important protein involved in dynein activation is LIS1 (Lissencephaly-1) (Markus et al, 2020). The mechanism of LIS1 action in the dynein pathway has been controversial, but multiple recent studies suggest that LIS1 promotes the open dynein conformation, thereby facilitating dynein activation (Qiu et al, 2019;Elshenawy et al, 2020;Htet et al, 2020;Marzo et al, 2020;McKenney, 2020). LIS1, a WD40-repeats-containing protein, was initially identified as a causal gene for type 1 lissencephaly, a human brain developmental disorder (Reiner et al, 1993).…”