Calcium/calmodulin-dependent protein kinase belonging to a proposed calcium-triggered signaling cascade involved in a number of cellular processes. Phosphorylates CAMK1, CAMK4 and CAMK1D (By similarity). Efficiently phosphorylates 5'-AMP-activated protein kinase (AMPK) trimer, including that consisting of PRKAA1, PRKAB1 and PRKAG1. This phosphorylation is stimulated in response to Ca(2+) signals (By similarity). May play a role in neurite growth. Isoform 2 may promote neurite elongation, while isoform 1 may promoter neurite branching (By similarity). May be involved in hippocampal activation of CREB1. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by Ca(2+)/calmodulin. Binding of calmodulin may relieve intrasteric autoinhibition. Autophosphorylation does not alter activity or regulation by Ca(2+)/calmodulin. In part, activity is independent on Ca(2+)/calmodulin (By similarity). Interacts with calmodulin. Predominantly nuclear in unstimulated cells, relocalizes into cytoplasm and neurites after forskolin induction. Expressed in all tissues tested. A differential expression pattern compared to CAMKK1 is observed in the brain. The autoinhibitory domain overlaps with the calmodulin binding region and may be involved in intrasteric autoinhibition. The RP domain (arginine/proline-rich) is involved in the recognition of CAMKI and CAMK4 as substrates. Autophosphorylated and phosphorylated by PKA. Each isoform may show a different pattern of phosphorylation. Mice are unable to form spatial long-term memory. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.