KN-93 phosphate is the water soluble form of KN-93. It is a potent, selective and cell permeable inhibitor of CaM kinase II (IC50= 0.37 μm, Ki=370 nm) [1]
CaMK II (calcium/calmodulin-dependent protein kinase II) is a multifunctional serine/threonine kinase with various roles in different physiological systems.
Since CaMK II can enhance cell proliferation, the CaMK II inhibitor KN-93 blocked the cell proliferation by regulating the expression of p53 and p21 in human hepatic stellate cells. [2] KN-93 inhibited the autophosphorylation of both α and β subunits of CaMK II. Moreover, KN-93 reduced dopamine level via modulating the TH reaction rate to reduce the Ca2+-mediated phosphorylation levels of the TH molecule in PC12h cells.[1] As CaMK II is necessary for cell cycle progression through G1, KN-93 also induced G1 cell cycle arrest and apoptosis in NIH 3T3 cells.[3]
In MRL/lpr Foxp3-GFP mice, KN-93 promoted the generation of Foxp3 regulatory T cells through the inhibition of CaMK IV in the spleen, peripheral lymph nodes and peripheral blood with decreased skin and kidney damage. [4] In a rat model of Parkinson's disease, intrastriatal injection of KN-93 relieved the levodopa-induced dyskinesia by suppressing the CaMK II activation. [5]
References:
[1] Sumi M, Kiuchi K, Ishikawa T, Ishii A, Hagiwara M, Nagatsu T, Hidaka H. The newly synthesized selective Ca2+/calmodulin dependent protein kinase II inhibitor KN-93 reduces dopamine contents in PC12h cells. Biochem Biophys Res Commun. 1991 Dec 31;181(3):968-75.
[2] An P, Zhu JY, Yang Y, Lv P, Tian YH, Chen MK, Luo HS. KN-93, a specific inhibitor of CaMKII inhibits human hepatic stellate cell proliferation in vitro. World J Gastroenterol. 2007 Mar 7;13(9):1445-8.
[3] Tombes RM, Grant S, Westin EH, Krystal G. G1 cell cycle arrest and apoptosis are induced in NIH 3T3 cells by KN-93, an inhibitor of CaMK-II (the multifunctional Ca2+/CaM kinase). Cell Growth Differ. 1995 Sep;6(9):1063-70.
[4] Koga T, Mizui M, Yoshida N, Otomo K, Lieberman LA, Crispín JC, Tsokos GC.KN-93, an inhibitor of calcium/calmodulin-dependent protein kinase IV, promotes generation and function of Foxp3? regulatory T cells in MRL/lpr mice. Autoimmunity. 2014 Nov;47(7):445-50.
[5] Yang X, Wu N, Song L, Liu Z. Intrastriatal injections of KN-93 ameliorates levodopa-induced dyskinesia in a rat model of Parkinson's disease. Neuropsychiatr Dis Treat. 2013;9:1213-20. doi: 10.2147/NDT.S45422.