Bjørn S Skålhegg ¹ and Kjetil Tasken ²

1 Institute for Nutrition Reserarch, and ² Institute of Medical Biochemistry, University of Oslo, Norway

TABLE OF CONTENTS

1. Abstract

2. Cyclic AMP and the cAMP-dependent protein kinase (PKA) signaling system

3. Isozymes of PKA

3.1. Multiple isoforms of regulatory and catalytic subunits of PKA
3.2. Features of regulatory and catalytic subunits of PKA

3.2.1. Structure of regulatory subunits
3.2.2. Structure of catalytic subunits

4. Levels and expression of the regulatory and catalytic subunits

5. PKA isozyme composition and characteristics

6. Specific effects of cAMP are mediated through subcellularly anchored PKA isozymes.

6.1. PKAI mediates specific effects of cAMP at distinct subcellular sites.
6.2. PKAII is targeted to subcellular structures via A kinase anchoring proteins (AKAPs) and mediates discrete cAMP responses.

7. AKAPs assemble signal complexes important for intracellular signaling.

8 Summary and perspectives

9 References

1 ABSTRACT

A large number of hormones, neurotransmitters and other signal substances utilize adenosine 3',5' cyclic monophosphate (cAMP) as an intracellular second messenger. Cyclic AMP regulates a number of different cellular processes such as cell growth and differentiation, ion channel conductivity, synaptic release of neurotransmitters, and gene transcription.The principle intracellular target for cAMP in mammalian cells is the cAMP-dependent protein kinase (PKA). The fact that this broad specificity protein kinase mediates a number of discrete physiological responses following cAMP-engagement, has raised the question of how specificity is maintained in the cAMP/PKA system. Here we will describe features of this signaling pathway that may contribute to explain how differential effects of cAMP may be contributed to features of the PKA signaling pathway.