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Epidermal growth factor modulates release of arachidonic acid from embryonic cells
1Department of Anatomy, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107.
Abstract:
The calcium ionophore A23187 stimulates release of free [3H]arachidonic acids from radiolabeled cultures of MEPM cells which are growing, but not from those which are confluent. However, when confluent MEPM cells are pretreated with EGF or PMA, release of [3H]arachidonic acids does occur in response to A23187. Since neither EGF nor PMA themselves stimulate release of [3H]arachidonic acids from these cells, but do activate protein kinase C, these data support the hypothesis that protein kinase C modulates the activities of phospholipid hydrolases in MEPM cells.
Insights
Calcium ionophore A23187 releases arachidonic acid from growing MEPM cells. Pretreatment with EGF or PMA enables release from confluent cells, suggesting protein kinase C modulates phospholipid hydrolase activity.
Area of Science:
- Cell biology
- Biochemistry
- Molecular signaling
Background:
- Arachidonic acid release is a key signaling event.
- MEPM cells exhibit differential responses to calcium ionophores based on growth state.
- Epidermal Growth Factor (EGF) and Phorbol 12-myristate 13-acetate (PMA) are known activators of protein kinase C.
Purpose of the Study:
- To investigate the role of protein kinase C in regulating [3H]arachidonic acid release in MEPM cells.
- To determine if EGF or PMA can overcome the inhibition of arachidonic acid release in confluent MEPM cells.
Main Methods:
- Radiolabeling of MEPM cells with [3H]arachidonic acid.
- Stimulation of cells with calcium ionophore A23187.
- Pretreatment of confluent cells with EGF or PMA.
- Measurement of released [3H]arachidonic acid.
Main Results:
- A23187 stimulated [3H]arachidonic acid release from growing MEPM cells, but not confluent cells.
- Pretreatment with EGF or PMA enabled A23187-induced [3H]arachidonic acid release from confluent MEPM cells.
- EGF and PMA alone did not stimulate [3H]arachidonic acid release, but activated protein kinase C.
Conclusions:
- Protein kinase C activation is necessary for EGF/PMA-induced modulation of phospholipid hydrolase activity in MEPM cells.
- These findings support a model where protein kinase C plays a crucial role in regulating arachidonic acid release pathways in MEPM cells.