Abstract
c-AMP enhances surfactant release from Type II epithelial cells, presumably by activation of protein kinases (PK) and increased protein phosphorylation. cAMP dependent (dep) phosphorylation of endogenous proteins was therefore assessed in rat lung during development and in adult Type II epithelial cells. Protein Mr=43,000 was the major substrate of c-AMP-PK in cytosol from postnatal lung and in purified adult Type II cells. Evidence that [32P]43,000 is the cytoskeletal protein, actin, includes migration on 2-D SDS-PAGE and phospho-peptide mapping. [32P]Serine was the only phosphoamino acid detected. Phosphorylation was reversible and entirely cAMP dep, EC50=5×10−7 M. cAMP dep 32P-actin was barely detectable until 21d gestation and increased 25-fold during the perinatal period. cAMP dep protein kinase activity did not correlate with developmental increase in 32P-actin. cAMP-PK was higher in fetal than adult preprations, p<.01. Lung actin content did not change with age. Addition of purified actin but not cAMP-PK to fetal cytosol enhanced 32P-actin. Actin is a major endogenous cytosolic substrate of c-AMP-PK in Type II epithelial cells and in postnatal lung. Actin phosphorylation is developmentally regulated in association with other aspects of lung maturation. Mechanisms that might account for the developmental changes in lung 32p-actin include 1) availability of actin to serve as substrate of c-AMP- PK, 2) new actin forms, or 3) ontogenic appearance of specific c-AMP dependent actin kinase activity.
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Whitsett, J., Lessard, J. APPEARANCE OF c-AMP DEPENDENT ACTIN PHOSPHORYLATION IN RAT LUNG AND TYPE II EPITHELIAL CELLS. Pediatr Res 18 (Suppl 4), 147 (1984). https://doi.org/10.1203/00006450-198404001-00326
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DOI: https://doi.org/10.1203/00006450-198404001-00326