DEVELOPMENTAL-CHANGES IN PHOSPHORYLATION OF THE TRANSCRIPTION FACTOR CREB IN THE EMBRYONIC MURINE PALATE

Cyclic AMP, via activation of cAMP-dependent protein kinase (PKA) and subsequent protein phosphorylation, regulates a number of cellular and tissue responses that are critical to normal development of the mamma lian palate. The present study examines the expression, distribution, and phosphorylation in the developing murine palate of a substrate for PKA known as the cAMP-response element binding protein (CREB). This 4 3 x 10(3) M(r) protein functions as a regulator of cAMP-inducible gene expression. CREB is expressed constituitively throughout the palatal morphogenetic period and is ubiquitously distributed throughout palata l tissue. Immunofluorescent staining of palatal cells and tissues with an anti-CREB antibody revealed CREB to be localized to cell nuclei. W estern blot analysis of extracts of staged palatal shelves with an ant ibody specific for phospho-ser 133-CREB demonstrated a steady increase in CREB phosphorylation at this residue during palate development. Th ese observations show a temporal correlation with expression levels of cAMP-regulated genes in palate cells. The data indicate that CREB act ivity in the developing palate is most likely to be regulated at the l evel of protein phosphorylation as opposed to changes in levels of CRE B protein expression. (C) 1995 Wiley-Liss, Inc.