The KN-93 Molecule Inhibits Calcium/Calmodulin-Dependent Protein Kinase II (CaMKII) Activity by Binding to Ca2+/CaM

作者：Melanie Wong, Alexandra B. Samal, Mike Lee, J. Vlach, Nikolai Novikov, Anita Niedziela‐Majka, Joy Y. Feng, Dmitry O. Koltun, Katherine M. Brendza, Hyock Joo Kwon, Brian E. Schultz, Roman Sakowicz, Jamil S. Saad, Giuseppe A. Papalia · 发表于：Journal of Molecular Biology · 年份：2019 · DOI：10.1016/j.jmb.2019.02.001 · 被引用次数：120 · 研究领域：Signaling Pathways in Disease、Protein Kinase Regulation and GTPase Signaling、Endoplasmic Reticulum Stress and Disease

Calcium/calmodulin-dependent protein kinase II (CaMKII) is a multifunctional serine/threonine protein kinase that transmits calcium signals in various cellular processes. CaMKII is activated by calcium-bound calmodulin (Ca2+/CaM) through a direct binding mechanism involving a regulatory C-terminal α-helix in CaMKII. The Ca2+/CaM binding triggers transphosphorylation of critical threonine residues proximal to the CaM-binding site leading to the autoactivated state of CaMKII. The demonstration of its critical roles in pathophysiological processes has elevated CaMKII to a key target in the management of numerous diseases. The molecule KN-93 is the most widely used inhibitor for studying the cellular and in vivo functions of CaMKII. It is widely believed that KN-93 binds directly to CaMKII, thus preventing kinase activation by competing with Ca2+/CaM. Herein, we employed surface plasmon resonance, NMR, and isothermal titration calorimetry to characterize this presumed interaction. Our results revealed that KN-93 binds directly to Ca2+/CaM and not to CaMKII. This binding would disrupt the ability of Ca2+/CaM to interact with CaMKII, effectively inhibiting CaMKII activation. Our findings also indicated that KN-93 can specifically compete with a CaMKIIδ-derived peptide for binding to Ca2+/CaM. As indicated by the surface plasmon resonance and isothermal titration calorimetry data, apparently at least two KN-93 molecules can bind to Ca2+/CaM. Our findings provide new insight into how...