Regulatory imbalance between LRRK2 kinase, PPM1H phosphatase, and ARF6 GTPase disrupts the axonal transport of autophagosomes

Dou, D.; Smith, E. M.; Evans, C. S.; Boecker, C. A.; Holzbaur, E. L. F.

doi:10.1101/2022.11.14.516471

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bioRxiv · 10.1101/2022.11.14.516471

Regulatory imbalance between LRRK2 kinase, PPM1H phosphatase, and ARF6 GTPase disrupts the axonal transport of autophagosomes

Dou, D.·Smith, E. M.·Evans, C. S.·Boecker, C. A.·Holzbaur, E. L. F.

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Abstract

Gain-of-function mutations in the LRRK2 gene cause Parkinsons disease (PD), increasing phosphorylation of RAB GTPases through hyperactive kinase activity. We found that LRRK2-hyperphosphorylated RABs disrupt the axonal transport of autophagosomes by perturbing the coordinated regulation of cytoplasmic dynein and kinesin motors. In iPSC-derived human neurons, knock-in of the strongly-hyperactive LRRK2-p.R1441H mutation caused striking impairments in autophagosome transport, inducing frequent directional reversals and pauses. Knock-out of the opposing Protein Phosphatase 1H (PPM1H) phenocopied the effect of hyperactive LRRK2. Overexpression of ADP-ribosylation factor 6 (ARF6), a GTPase that acts as a switch for selective activation of dynein or kinesin, attenuated transport defects in both p.R1441H knock-in and PPM1H knock-out neurons. Together, these findings support a model where a regulatory imbalance between LRRK2-hyperphosphorylated RABs and ARF6 induces an unproductive "tug-of-war" between dynein and kinesin, disrupting processive autophagosome transport. This disruption may contribute to PD pathogenesis by impairing the essential homeostatic functions of axonal autophagy.

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Dou, D., Smith, E. M., Evans, C. S., Boecker, C. A., Holzbaur, E. L. F.. 2022-11-14. Regulatory imbalance between LRRK2 kinase, PPM1H phosphatase, and ARF6 GTPase disrupts the axonal transport of autophagosomes. https://doi.org/10.1101/2022.11.14.516471

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