Phospho-substrate profiling of Epac-dependent protein kinase C activity

Area of Science:

• Cellular signaling pathways
• Molecular biology
• Neuroscience

Background:

• Cyclic AMP (cAMP) signaling involves effectors like Epac and protein kinase A (PKA).
• Epac activates Rap1, a GTPase that triggers downstream signaling, including protein kinase C (PKC).
• Epac-PKC signaling is implicated in cardiac hypertrophy, cancer, and chronic pain, yet its specific targets remain largely unknown.

Purpose of the Study:

• To characterize the regulation of PKC activity downstream of Epac activation.
• To identify specific PKC substrates modulated by Epac signaling.
• To investigate the role of the cytoskeleton in Epac-dependent PKC signaling.

Main Methods:

• Utilized a phospho-specific antibody to detect PKC-phosphorylated substrates in Neuro2A cells.
• Activated Epac directly (8pCpt) or indirectly (PGE2) and analyzed PKC substrate phosphorylation profiles.
• Employed Epac and isoform-selective PKC inhibitors to dissect signaling pathways.
• Investigated the effect of cytoskeletal disruption on Epac-induced PKC activity.

Main Results:

• Epac activation, via prostaglandin E2 or 8-pCPT-2-O-Me-cAMP-AM, induced distinct PKC phospho-substrate protein bands.
• These induced bands were suppressed by the Epac inhibitor ESI09.
• Different PKC isoforms were responsible for phosphorylating specific substrates.
• Cytoskeletal disruption altered the pattern of Epac-dependent PKC substrate phosphorylation.

Conclusions:

• Epac activation leads to specific PKC substrate phosphorylation events.
• The study provides a method to characterize Epac-dependent PKC activity.
• Cytoskeletal interactions play a role in orchestrating Epac-mediated PKC signaling.