Surfactant secretion in LRRK2 knock-out rats: changes in lamellar body morphology and rate of exocytosis.
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.
Institute of General Physiology, University of Ulm, Ulm, Germany.
Pika
P
Miklavc
Institute of General Physiology, University of Ulm, Ulm, Germany.
Konstantin
K
Ehinger
Institute of General Physiology, University of Ulm, Ulm, Germany.
Kristin E
KE
Thompson
Institute of General Physiology, University of Ulm, Ulm, Germany ; Department of Physiology and Medical Physics, Innsbruck Medical University, Innsbruck, Austria.
Nina
N
Hobi
Department of Autoimmunity/Transplantation/Inflammation-Neuroscience, Novartis Institutes for BioMedical Research, Basel, Switzerland.
Derya R
DR
Shimshek
Institute of General Physiology, University of Ulm, Ulm, Germany.
Manfred
M
Frick
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D005089:Exocytosis / Q000187:drug effects / Q000235:genetics*; D017353:Gene Deletion; D015870:Gene Expression; D000071158:Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; D015388:Organelles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency* / Q000235:genetics; D011650:Pulmonary Alveoli / Q000378:metabolism* / Q000473:pathology; D011663:Pulmonary Surfactants / Q000378:metabolism*; D051381:Rats; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
D015415:Biomarkers; D011663:Pulmonary Surfactants; D000255:Adenosine Triphosphate; C547428:LRRK2 protein, rat; D000071158:Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; D017346:Protein Serine-Threonine Kinases; D002118:Calcium