Surfactant secretion in LRRK2 knock-out rats: changes in lamellar body morphology and rate of exocytosis

PLoS One. 2014 Jan 21;9(1):e84926. doi: 10.1371/journal.pone.0084926. eCollection 2014.

Abstract

Leucine-rich repeat kinase 2 (LRRK2) is known to play a role in the pathogenesis of various diseases including Parkinson disease, morbus Crohn, leprosy and cancer. LRRK2 is suggested to be involved in a number of cell biological processes such as vesicular trafficking, transcription, autophagy and lysosomal pathways. Recent histological studies of lungs of LRRK2 knock-out (LRRK2 -/-) mice revealed significantly enlarged lamellar bodies (LBs) in alveolar type II (ATII) epithelial cells. LBs are large, lysosome-related storage organelles for pulmonary surfactant, which is released into the alveolar lumen upon LB exocytosis. In this study we used high-resolution, subcellular live-cell imaging assays to investigate whether similar morphological changes can be observed in primary ATII cells from LRRK2 -/- rats and whether such changes result in altered LB exocytosis. Similarly to the report in mice, ATII cells from LRRK2 -/- rats contained significantly enlarged LBs resulting in a >50% increase in LB volume. Stimulation of ATII cells with ATP elicited LB exocytosis in a significantly increased proportion of cells from LRRK2 -/- animals. LRRK2 -/- cells also displayed increased intracellular Ca(2+) release upon ATP treatment and significant triggering of LB exocytosis. These findings are in line with the strong Ca(2+)-dependence of LB fusion activity and suggest that LRRK2 -/- affects exocytic response in ATII cells via modulating intracellular Ca(2+) signaling. Post-fusion regulation of surfactant secretion was unaltered. Actin coating of fused vesicles and subsequent vesicle compression to promote surfactant expulsion were comparable in cells from LRRK2 -/- and wt animals. Surprisingly, surfactant (phospholipid) release from LRRK2 -/- cells was reduced following stimulation of LB exocytosis possibly due to impaired LB maturation and surfactant loading of LBs. In summary our results suggest that LRRK2 -/- affects LB size, modulates intracellular Ca(2+) signaling and promotes LB exocytosis upon stimulation of ATII cells with ATP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Animals
  • Biomarkers / metabolism
  • Calcium / metabolism
  • Calcium Signaling*
  • Exocytosis / drug effects
  • Exocytosis / genetics*
  • Gene Deletion
  • Gene Expression
  • Leucine-Rich Repeat Serine-Threonine Protein Kinase-2
  • Organelles / drug effects
  • Organelles / metabolism*
  • Organelles / ultrastructure
  • Protein-Serine-Threonine Kinases / deficiency*
  • Protein-Serine-Threonine Kinases / genetics
  • Pulmonary Alveoli / metabolism*
  • Pulmonary Alveoli / pathology
  • Pulmonary Surfactants / metabolism*
  • Rats
  • Secretory Vesicles / drug effects
  • Secretory Vesicles / metabolism
  • Secretory Vesicles / ultrastructure

Substances

  • Biomarkers
  • Pulmonary Surfactants
  • Adenosine Triphosphate
  • LRRK2 protein, rat
  • Leucine-Rich Repeat Serine-Threonine Protein Kinase-2
  • Protein-Serine-Threonine Kinases
  • Calcium

Grant support

This work was funded by BiU grant D.5006 and DFG grant D-1402/3-1 (www.dfg.de). P.M. is supported by a Margarete von Wrangell fellowship from the Ministry of Science, Research and the Arts Baden-Württemberg (www.margarete-von-wrangell.de). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.