ITPKA

ITPKA is one of three inositol-trisphosphate 3-kinase (ITP3K) genes in humans. ITP3K proteins regulate inositol phosphate metabolism by phosphorylation of the second messenger inositol 1,4,5-trisphosphate to produce Ins(1,3,4,5)P4, which is sometimes abbreviated as IP4. Structurally, ITPKA belongs to the inositol polyphosphate kinase (IPK) family. The activity of the inositol 1,4,5-trisphosphate 3-kinase is responsible for regulating the levels of a large number of inositol polyphosphates that are important in cellular signaling, most notably, inositol trisphosphate, which is the enzyme's only substrate. Both calcium/calmodulin and protein phosphorylation mechanisms control its activity. It is also a substrate for the cyclic AMP-dependent protein kinase, calcium/calmodulin- dependent protein kinase II, and protein kinase C in vitro. ITPKA and ITPKB are 68% identical in the C-terminus region The amino- terminal region of ITPKA binds filamentous actin. This property localizes the ITPKA to dendritic spines in principal neurons.^[4][5][6] ITPKA is expressed physiologically in neurons, but it is sometimes expressed in cancer cells and may contribute to processes of metastasis.^[7]

ITPKA participates in learning and memory processes in neurons.^[8][9]

Although ITPKA is expressed physiologically in neurons and testis, it sometimes becomes expressed in cancer cells, and the expression usually makes the cancer more aggressive.^[7][10]

F-tractin is amino acids 9-52 of rat ITPKA. It was later determined that amino acids 9-40 were sufficient for binding filamentous actin.^[11][12] When fused to a reporter, such as green fluorescent protein, It is useful for the visualization of actin dynamics in living cells.^[13][14]