Published ahead of print on October 23, 2008, doi:10.1165/rcmb.2008-0284OC
© 2009 American Thoracic Society DOI: 10.1165/rcmb.2008-0284OC Global and Gene-Specific Translational Regulation in Rat Lung Development1 Canadian Institutes of Health Research Group in Lung Development, and Program in Physiology and Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada; 2 Department of Paediatrics, University of Toronto, Toronto, Canada; and 3 Department of Pediatrics, Stanford University School of Medicine, Stanford, California Correspondence and requests for reprints should be addressed to Gail Otulakowski, Ph.D., Program in Physiology and Experimental Medicine, Hospital for Sick Children Research Institute, 555 University Avenue, Toronto, ON, M5G 1X8 Canada. Email: gail.otulakowski{at}sickkids.ca During the peripartum period, the lung must respond to dramatic changes in circulating hormones, nutritional factors, and physiologic signals during its transition to becoming the organ of gas exchange. Protein synthesis consumes a significant proportion of metabolic resources and is inhibited by many environmental stresses. We hypothesized that translational control mechanisms play a role in the perinatal lung. Immunoblots of late-gestation (Fetal Day [FD] 17–22) rat lung extracts revealed gradual decreases in phosphorylated forms of the mammalian target of rapamycin effectors, eukaryotic initiation factor (eIF) 4E–binding protein, p70 S6 kinase, and ribosomal protein S6, followed by sharp increases on Postnatal Day 1 (P1). Immunohistochemistry showed phospho-S6 staining was most prominent in epithelial cells of the large and small airways. m7GTP-sepharose pulldown experiments showed a decrease in association of translation initiation factor, eIF4E, with its inhibitor, eIF4E–binding protein, and a concomitant increase in eIF4E association with eIF4G immediately after birth, and polysome profiles confirmed a decrease in abundance of large polysomes between FD19 and FD22, which was reversed on P1. Microarray analysis of polysomal versus total RNA from FD19, FD22, and P1 lungs was used to identify specific genes, the association of which with large polysomes changed either pre- or postnatally. RT-PCR and Northern blotting were used to confirm translational changes in selected candidate genes, including a prenatal increase in IL-18 and a postnatal decrease in regulatory subunit 2 of protein phosphatase 1. Translational regulation of IL-18 and protein phosphatase 1 regulatory (inhibitor) subunit 2 is gene-specific, as these changes contrast with the corresponding global changes in polysome abundance.
Key Words: lung development • protein synthesis • microarray • polysome • translation This article has been cited by other articles:
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