Protein phosphorylation in human placenta. Stimulation by epidermal growth factor

Area of Science:

• Biochemistry
• Cell Biology
• Human Physiology

Background:

• Cellular signaling pathways often involve protein phosphorylation.
• Epidermal growth factor (EGF) is a key regulator of cell growth and differentiation.
• The role of EGF in placental tissue phosphorylation requires further elucidation.

Purpose of the Study:

• To investigate the presence and characteristics of protein kinase activity in human term placenta membranes.
• To determine the effect of epidermal growth factor (EGF) on protein phosphorylation in placental tissue.
• To identify specific placental proteins whose phosphorylation is modulated by EGF.

Main Methods:

• Preparation of normal human term placenta membranes.
• Assay of protein kinase activity using [gamma-32P]ATP in the presence of divalent cations (Mg2+ or Mn2+).
• Analysis of protein phosphorylation by sodium dodecyl sulfate gel electrophoresis and autoradiography following EGF stimulation.

Main Results:

• Human term placenta membranes exhibit intrinsic protein kinase activity.
• This activity is Mg2+/Mn2+-dependent, glycerol-enhanced, and cyclic-nucleotide-independent.
• Epidermal growth factor (EGF) stimulation increased total protein phosphorylation by approximately 35%.
• EGF-enhanced phosphorylation was observed for proteins with apparent molecular weights of 170,000, 150,000, and 25,000.

Conclusions:

• Protein kinase activity is present in normal human term placenta.
• Epidermal growth factor (EGF) modulates protein phosphorylation in human placental tissue.
• Specific placental proteins are targets for EGF-mediated phosphorylation, suggesting a role for EGF signaling in placental function.