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Cyclic AMP-dependent protein phosphorylation in the rat anterior pituitary
S T Cain1, J C Pryor, C B Nemeroff
1Department of Psychiatry, Duke University Medical Center, Durham, North Carolina 27710.
Abstract:
The activation of cyclic adenosine 3'5'-monophosphate (cAMP)-dependent protein kinases has been implicated as an integral mechanism in stimulus-secretion coupling in the anterior pituitary. Therefore, we have investigated phosphorylation of endogenous protein substrates both in the presence and absence of cAMP in cell-free extracts of the rodent anterior pituitary. Specific phosphoprotein substrates in the rat anterior pituitary, which are phosphorylated by a cAMP-dependent protein kinase in vitro, were identified. Cyclic AMP potentiated the phosphorylation of proteins with apparent molecular weights of 85,000, 77,000, 63,000, 53,000, 39,000, and 33,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Proteins with apparent molecular weights of 124,000, 93,000, 48,000, and 43,000 were phosphorylated only in the presence of cAMP and not in the basal condition. The results highlight endogenous protein substrates that may potentially be involved in cAMP-dependent stimulus-secretion coupling in the anterior pituitary.
Insights
Cyclic adenosine monophosphate (cAMP) activates protein kinases in the anterior pituitary, influencing hormone secretion. This study identified specific proteins phosphorylated by cAMP, revealing key players in stimulus-secretion coupling.
Area of Science:
- Endocrinology
- Molecular Biology
- Cellular Signaling
Background:
- Cyclic adenosine 3'5'-monophosphate (cAMP)-dependent protein kinases are crucial for stimulus-secretion coupling in the anterior pituitary.
- Understanding the specific protein substrates involved in this process is essential for elucidating pituitary function.
Purpose of the Study:
- To identify endogenous protein substrates phosphorylated by cAMP-dependent protein kinases in the rodent anterior pituitary.
- To investigate the role of cAMP in modulating protein phosphorylation in cell-free pituitary extracts.
Main Methods:
- Cell-free extracts from rodent anterior pituitary were used.
- Protein phosphorylation was analyzed in the presence and absence of cAMP.
- Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was employed to determine the molecular weights of phosphoproteins.
Main Results:
- cAMP potentiated the phosphorylation of proteins with molecular weights of 85,000, 77,000, 63,000, 53,000, 39,000, and 33,000.
- Proteins with molecular weights of 124,000, 93,000, 48,000, and 43,000 were exclusively phosphorylated in the presence of cAMP.
Conclusions:
- Specific endogenous phosphoprotein substrates involved in cAMP-dependent stimulus-secretion coupling in the anterior pituitary were identified.
- These findings provide insights into the molecular mechanisms regulating hormone release from the anterior pituitary.