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

Cell Rep. 2023 May 30;42(5):112448. doi: 10.1016/j.celrep.2023.112448. Epub 2023 May 1.

Abstract

Gain-of-function mutations in the LRRK2 gene cause Parkinson's disease (PD), increasing phosphorylation of RAB GTPases through hyperactive kinase activity. We find that LRRK2-hyperphosphorylated RABs disrupt the axonal transport of autophagosomes by perturbing the coordinated regulation of cytoplasmic dynein and kinesin. In iPSC-derived human neurons, knockin of the strongly hyperactive LRRK2-p.R1441H mutation causes striking impairments in autophagosome transport, inducing frequent directional reversals and pauses. Knockout of the opposing protein phosphatase 1H (PPM1H) phenocopies 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, attenuates transport defects in both p.R1441H knockin and PPM1H knockout 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.

Keywords: ARF6; CP: Cell biology; LRRK2; PPM1H; Parkinson’s disease; RAB GTPases; autophagy; axonal transport; cytoplasmic dynein; kinesin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADP-Ribosylation Factor 6
  • Autophagosomes / metabolism
  • Axonal Transport / physiology
  • Dyneins / metabolism
  • GTP Phosphohydrolases* / metabolism
  • Humans
  • Kinesins / genetics
  • Kinesins / metabolism
  • Leucine-Rich Repeat Serine-Threonine Protein Kinase-2 / genetics
  • Leucine-Rich Repeat Serine-Threonine Protein Kinase-2 / metabolism
  • Mutation
  • Parkinson Disease* / pathology
  • Phosphoprotein Phosphatases / metabolism
  • Phosphorylation

Substances

  • ADP-Ribosylation Factor 6
  • Dyneins
  • GTP Phosphohydrolases
  • Kinesins
  • Leucine-Rich Repeat Serine-Threonine Protein Kinase-2
  • LRRK2 protein, human
  • Phosphoprotein Phosphatases
  • PPM1H protein, human
  • ARF6 protein, human