Neuronal calcium sensor-1

NCS1 or neuronal calcium sensor-1 is a member of Neuronal calcium sensor family which, are EF hand containing calcium-myristoyl-switch proteins. This neuronal protein is called frequenin in the invertebrates and thus named homolog of Drosophila Frequenin and its official symbol is FREQ. Its level is supposed to increase in Bipolar disorder and some Schizophrenia, and reduced in human X-linked mental retardation and chronic inflammatory bowel diseases. It is a calcium sensor, not a calcium buffer (chelator); thus it is a high-affinity, low-capacity, calcium-binding protein.

Functions
FREQ can substitute for calmodulin in some situations. It is thought to be assocuated with neuronal secretpry vesicles and regulate neurosecretion.
 * 1) It is the Ca2+-sensing subunit of the yeast phosphatidylinositol (PtdIns)-4-OH kinase, PIK1
 * 2) It binds to many proteins, some in calcium dependent and some in calcium independent ways, and switches many of the targets "on" (some off).
 * 3) Calcineurin (protein phosphatase 2B)
 * 4) GRK2 (G-protein-coupled receptor kinase 2)
 * 5) D2 Dopamine receptor
 * 6) IL1RAPL (interleukin-1 receptor accessory protein-like protein)
 * 7) PI4KIIIβ (type III phosphatidylinositol 4-kinase β)
 * 8) IP3 receptor (This activity is inhibited by Lithium- the main drug for Bipolar disorder
 * 9) 3',5'-cyclic nucleotide phosphodiesterases
 * 10) ARF1 (ADP Ribosylation factor 1)
 * 11) A type (Kv4.3; Shal-related subfamily, member 3) voltage gated potassium channels
 * 12) Nitric oxide synthase
 * 13) TRPC5 channel (Hui et al, J Physiol. 2006 Apr 1;572(Pt 1):165-72)