| Modification Notes |
The second messenger cyclic AMP (cAMP) mediates a diverse array of cellular responses such as proliferation, ion transport, regulation of metabolism and gene transcription by activating the cAMP-dependent protein kinase (cAPK or PKA). Activation of PKA occurs when cAMP binds to the two regulatory subunits of tetrameric PKA, resulting in the release of two active catalytic subunits. Two forms of a specific PKA inhibitor molecule, designated pki a and pki b, have been described and are suggested to regulate PKA activity in different portions of the central nervous system. For instance, pki a is ex-pressed abundantly in the adult mouse brain, particularly in the cerebellum, hypothalamus, hippocampus and cortex. In constrast, pki b is present at a much lower level in most brain regions, and is found in significant amounts only in the cerebellum and in a few distinct nuclei within the pons, medulla and hypothalamus. |