KN-93 (phosphate) is a potent and selective inhibitor of Ca2+/calmodulin-dependent kinase II (CaMKII) (Ki = 370 nM), inhibiting both the α- and β-subunits of CaMKII. It does not have significant effects on cAMP-dependent protein kinase, Ca2+/phospholipid-dependent protein kinase, myosin light chain kinase, or Ca2+ phosphodiesterase activity. It inhibits histamine-induced aminopyrine uptake in parietal cells (IC50 = 300 nM). KN-93 can block voltage-gated potassium (Kv) channels when applied extracellularly, independent of its CaMKII action. More recently, KN-93 has been used to implicate roles for CaMKII in Ca2+-induced Ca2+ release in cardiac myocytes, constitutive phosphorylation of 5-lipoxygenase in 3T3 cells, and Ca2+-dependent activation of HIF-1α in colon cancer cells.
