Signalling
cAMP-dependent protein kinase (PKA)
Some cAMP mediated responses are rapid (seconds)
- Skeletal muscle cells
- Activated PKA phosphorylates enzymes involved in glycogen
metabolism
- Triggering breakdown of glycogen → glucose
- Inhibiting glycogen synthesis
- ↑ glucose available to the muscle cell
Some are slow (hours)
- Somatostatin (peptide hormone) secreting cells
- cAMP response element (CRE), CRE binding unit (CREB)
- cAMP activates the gene encoding the hormone
- Regulatory region = CRE, a short sequence of DNA
- A specific gene regulatory protein (CREB) recognizes this sequence
- When CREB is phosphorylated by PKA it recruits a transcriptional
coactivator CREB-binding protein (CBP)
- CBP stimultes transcription of the genes
