P2X7R-dependent regulation of glycogen synthase kinase 3β and claudin-18 in alveolar epithelial type I cells of mice lung.
The purinergic receptor P2X7 represents an ATP-gated ionotropic receptor with a selective localization in alveolar epithelial type I cells of the lung. Despite the involvement of the receptor in inflammatory processes of the lung, it is not established whether this receptor plays a specific role in the alveolar epithelial cell biology. There is evidence that P2X7 receptor influences Wnt/β-catenin signalling pathways in alveolar epithelial cells under conditions of injury. Here, we investigated the expression of GSK-3β, a potent protein kinase involved in alveolar epithelial barrier functions, and of tight junction molecules occludin, claudin-4 and claudin-18 in wild-type and P2X7-/-mice. Western blot analysis, immunohistochemistry and quantitative real-time RT-PCR revealed a remarkable increase in claudin-18 mRNA and protein in lungs of P2X7-/-mice animals. Furthermore, alveolar epithelial cells from P2X7-/-animals showed decreased levels of GSK-3β protein and its inactive form GSK-3β (pS9). Conversely, claudin-18 knockout mice exhibited decreased P2X7 mRNA transcript abundance as measured by mRNA expression microarray and quantitative PCR. Our data are consistent with the hypothesis that P2X7R contributes to alveolar epithelial barrier function through effects on GSK-3β. Furthermore, these data suggest a potential reciprocal regulation of claudin-18 and P2X7R in the alveolar epithelium.
Institute of Anatomy, Medical Faculty "Carl Gustav Carus", Technical University Dresden, Fetscherstr. 74, 01307, Dresden, Germany.
K
K
Barth
Institute of Anatomy, Medical Faculty "Carl Gustav Carus", Technical University Dresden, Fetscherstr. 74, 01307, Dresden, Germany.
R
R
Bläsche
Institute of Anatomy, Medical Faculty "Carl Gustav Carus", Technical University Dresden, Fetscherstr. 74, 01307, Dresden, Germany.
A
A
Neißer
Institute of Anatomy, Medical Faculty "Carl Gustav Carus", Technical University Dresden, Fetscherstr. 74, 01307, Dresden, Germany.
S
S
Bramke
San Francisco VA Medical Center, University of California, San Francisco, 4150 Clement St, Box 111D, San Francisco, CA, 94121, USA.
J A
JA
Frank
Institute of Anatomy, Medical Faculty "Carl Gustav Carus", Technical University Dresden, Fetscherstr. 74, 01307, Dresden, Germany. michael.kasper@tu-dresden.de.
M
M
Kasper
D056809:Alveolar Epithelial Cells / Q000378:metabolism*; D000818:Animals; D057167:Claudins / Q000172:deficiency / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta / Q000378:metabolism*; D008168:Lung / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D058486:Receptors, Purinergic P2X7 / Q000172:deficiency / Q000378:metabolism*
D057167:Claudins; C438899:Cldn18 protein, mouse; D058486:Receptors, Purinergic P2X7; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse
GSK-3β; Knockout; Mouse lung; P2X7 receptor; claudin-18; β-catenin
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