RETRACTED: L-Type Ca2+ Channel Facilitation Mediated by Phosphorylation of the β Subunit by CaMKII

Abstract

L-type Ca(2+) channels (LTCCs) are major entry points for Ca(2+) in many cells. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is associated with cardiac LTCC complexes and increases channel open probability (P(O)) to dynamically increase Ca(2+) current (I(Ca)) and augment cellular Ca(2+) signaling by a process called facilitation. However, the critical molecular mechanisms for CaMKII localization to LTCCs and I(Ca) facilitation in cardiomyocytes have not been defined. We show CaMKII binds to the LTCC beta(2a) subunit and preferentially phosphorylates Thr498 in beta(2a). Mutation of Thr498 to Ala (T498A) in beta(2a) prevents CaMKII-mediated increases in the P(O) of recombinant LTCCs. Moreover, expression of beta(2a)(T498A) in adult cardiomyocytes ablates CaMKII-mediated I(Ca) facilitation, demonstrating that phosphorylation of beta(2a) at Thr498 modulates native calcium channels. These findings reveal a molecular mechanism for targeting CaMKII to LTCCs and facilitating I(Ca) that may modulate Ca(2+) entry in diverse cell types coexpressing CaMKII and the beta(2a) subunit.

Diversity and Developmental Expression of L-type Calcium Channel β2 Proteins and Their Influence on Calcium Current in Murine Heart

“…Whereas numerous studies described cloning of Ca 2ϩ channel subunits and Ca 2ϩ channel composition in the human, guinea pig, and rat heart (5,7,25,29,39,40,41) the molecular "make-up" of the mouse cardiac LTCC is much less defined, although several mouse lines have been created with Ca 2ϩ channel subunit transgenes as preclinical models for heart diseases (22,23,24,42,43).…”

“…Recent mouse models (e.g. 22,23,24) carrying a rat CaV␤2 splice variant ("rat CaV␤2a") (25) expressed in rat and rabbit brain (26), but not in rabbit heart (26), have only escalated this requirement, because it has never been shown that the mouse orthologue of this variant is endogenously expressed in the mouse heart. So far, five CaV␤2 variants varying only in the V1 domain have been identified from different species (25,27,28) and in human heart these variants have been obtained mainly by RT-PCR approaches (29,30).…”

The δ isoform of CaM kinase II is required for pathological cardiac hypertrophy and remodeling after pressure overload

“…In the heart, CaMKII has been implicated in excitation-contraction (EC) coupling, gene transcription, and apoptosis (5,17). Many substrates involved in EC coupling such as phospholamban (PLB), the ryanodine receptor (RyR) and the L-type Ca 2ϩ channel (LTCC) have been reported (17)(18)(19)(20)(21)(22). We have also demonstrated that CaMKII isoforms associate specifically with histone deacetylase 4 (HDAC4), a transcriptional repressor (23) that, when phosphorylated, dissociates from the MEF2 transcription factor and translocates from the nucleus to the cytoplasm through its association with the 14-3-3 chaperone protein (18).…”

Mitochondrial‐Mediated Oxidative Ca 2+ /Calmodulin‐Dependent Kinase II Activation Induces Early Afterdepolarizations in Guinea Pig Cardiomyocytes: An In Silico Study

“…A growing body of evidence has demonstrated that CaMKII can also be activated by ROS 21, 22, 23, 24. Once activated, CaMKII can phosphorylate a wide range of key Ca 2+ and Na + regulatory proteins such as LCCs,25, 26, 27, 28 RyRs,29, 30, 31, 32, 33, 34, 35 phosphalamban,29, 34, 36 and Na + channels 37, 38. Importantly, Xie et al39 showed that H 2 O 2 perfusion–induced oxidative CaMKII activation leads to afterdepolarizations in isolated rabbit cardiomyocytes, likely by phosphorylation of Na + channels and LCCs.…”