PKA (Protein kinase A) is a Ser/Thr phosphoryl transferase that transfers the γ-phosphate group of ATP to protein substrates. PKA phosphorylates more than 100 cytoplasmic and membrane associated targets. PKA mediates a myriad of cellular signaling events and its activity is tightly regulated both in space and time.
PKA is an evolutionarily conserved negative regulator of the hedgehog (Hh) signal transduction pathway. PKA is known to be required for the proteolytic processing event that generates the repressor forms of the Ci and Gli transcription factors that keep target genes off in the absence of Hh.