Tissue-specific expression of mRNAs for three distinct types of rat calmodulin-dependent protein kinase II

Challenges and Opportunities for Therapeutic Targeting of Calmodulin Kinase II in Heart

Heart failure remains a major health burden around the world. Despite great progress in delineation of molecular mechanisms underlying development of disease, standard therapy has not advanced at the same pace. The multifunctional signaling molecule Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) has received considerable attention over recent years for its central role in maladaptive remodeling and arrhythmias in the setting of chronic disease. However, these basic science discoveries have yet to translate into new therapies for human patients. This review addresses both the promise and barriers to developing translational therapies that target CaMKII signaling to abrogate pathologic remodeling in the setting of chronic disease. Efforts in small molecule design are discussed, as well as alternative targeting approaches that exploit novel avenues for compound delivery and/or genetic approaches to affect cardiac CaMKII signaling. These alternative strategies provide hope for overcoming some of the challenges that have limited the development of new therapies.

The roles of CaMKII and F-actin in the structural plasticity of dendritic spines: a potential molecular identity of a synaptic tag?

Ca2+/calmodulin-dependent protein kinase II (CaMKII) and actin are two crucial molecules involved in long-term potentiation (LTP). In addition to its signaling function, CaMKII plays a structural role via direct interaction with actin filaments, thus coupling functional and structural plasticity in dendritic spines. The status of F-actin, regulated by CaMKII, determines the postsynaptic protein binding capacity and thus may act as a synaptic tag that consolidates LTP.

Calmodulin kinase II is required for angiotensin II-mediated vascular smooth muscle hypertrophy

Despite our understanding that medial smooth muscle hypertrophy is a central feature of vascular remodeling, the molecular pathways underlying this pathology are still not well understood. Work over the past decade has illustrated a potential role for the multifunctional calmodulin-dependent kinase CaMKII in smooth muscle cell contraction, growth, and migration. Here we demonstrate that CaMKII is enriched in vascular smooth muscle (VSM) and that CaMKII inhibition blocks ANG II-dependent VSM cell hypertrophy in vitro and in vivo. Specifically, systemic CaMKII inhibition with KN-93 prevented ANG II-mediated hypertension and medial hypertrophy in vivo. Adenoviral transduction with the CaMKII peptide inhibitor CaMKIIN abrogated ANG II-induced VSM hypertrophy in vitro, which was augmented by overexpression of CaMKII-delta2. Finally, we identify the downstream signaling components critical for ANG II- and CaMKII-mediated VSM hypertrophy. Specifically, we demonstrate that CaMKII induces VSM hypertrophy by regulating histone deacetylase 4 (HDAC4) activity, thereby stimulating activity of the hypertrophic transcription factor MEF2. MEF2 transcription is activated by ANG II in vivo and abrogated by the CaMKII inhibitor KN-93. Together, our studies identify a complete pathway for ANG II-triggered arterial VSM hypertrophy and identify new potential therapeutic targets for chronic human hypertension.

The Role of Calmodulin Kinase II in Myocardial Physiology and Disease

The multifunctional Ca2+/calmodulin-dependent protein kinase II (CaMKII) regulates a rich variety of downstream targets in heart. Ca2+ homeostatic proteins are important CaMKII targets that support myocardial excitation-contraction coupling. Under stress conditions, excessive CaMKII activity promotes heart failure and arrhythmias, in part through actions at Ca2+ homeostatic proteins. Here, we briefly review the molecular and cellular physiology of CaMKII in myocardium.

Role of Ca2+/calmodulin-dependent kinases in skeletal muscle plasticity

In skeletal muscle, the increase in intracellular Ca(2+) resulting from motor activation plays a key role in both contractile activity-dependent and fiber type-specific gene expression. These motor activation-dependent signals are linked to the amplitude and duration of the Ca(2+) transients that are decoded downstream by Ca(2+)-dependent transcriptional pathways. Evidence is mounting that the Ca(2+)/calmodulin-dependent kinases (CaMKs) such as CaMKII play an important role in regulating oxidative enzyme expression, mitochondrial biogenesis, and expression of fiber type-specific myofibrillar proteins. CaMKIV has been shown to promote mitochondrial biogenesis and a mild fast-to-slow fiber type transition but has recently been shown to not be required for activity-dependent changes in muscle phenotype. CaMKII is known to decode frequency-dependent information and is activated during hypertrophic growth and endurance adaptations and also is upregulated during muscle atrophy. CaMKII has also been shown to remain active in a Ca(2+)-independent manner after acute and prolonged exercise, and, therefore, is implicated as a mechanism for muscle memory. This mechanism can sense altered functional demands and trigger activation of an adaptational response that is dose dependently related to the activation level. This class of enzymes may therefore be the ideal decoders of information encoded by the intensity, frequency, and duty cycle of muscle activation and thus translate level of muscle activation into phenotypic adaptations through regulation of important muscle genes.

Coordinate downregulation of CaM kinase II and phospholamban accompanies contractile phenotype transition in the hyperthyroid rabbit soleus

This study investigated the effects of l-thyroxine-induced hyperthyroidism on Ca2+/calmodulin (CaM)-dependent protein kinase (CaM kinase II)-mediated sarcoplasmic reticulum (SR) protein phosphorylation, SR Ca2+pump (Ca2+-ATPase) activity, and contraction duration in slow-twitch soleus muscle of the rabbit. Phosphorylation of Ca2+-ATPase and phospholamban (PLN) by endogenous CaM kinase II was found to be significantly lower (30–50%) in soleus of the hyperthyroid compared with euthyroid rabbit. Western blotting analysis revealed higher levels of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) 1 (∼150%) Ca2+pump isoform, unaltered levels of SERCA2 Ca2+pump isoform, and lower levels of PLN (∼50%) and δ-, β-, and γ-CaM kinase II (40 ∼ 70%) in soleus of the hyperthyroid rabbit. SR vesicles from hyperthyroid rabbit soleus displayed approximately twofold higher ATP-energized Ca2+uptake and Ca2+-stimulated ATPase activities compared with that from euthyroid control. The Vmaxof Ca2+uptake (in nmol Ca2+·mg SR protein−1·min−1: euthyroid, 818 ± 73; hyperthyroid, 1,649 ± 90) but not the apparent affinity of the Ca2+-ATPase for Ca2+(euthyroid, 0.97 ± 0.02 μM, hyperthyroid, 1.09 ± 0.04 μM) differed significantly between the two groups. CaM kinase II-mediated stimulation of Ca2+uptake by soleus muscle SR was ∼60% lower in the hyperthyroid compared with euthyroid. Isometric twitch force of soleus measured in situ was significantly greater (∼36%), and the time to peak force and relaxation time were significantly lower (∼30–40%), in the hyperthyroid. These results demonstrate that thyroid hormone-induced transition in contractile properties of the rabbit soleus is associated with coordinate downregulation of the expression and function of PLN and CaM kinase II and selective upregulation of the expression and function of SERCA1, but not SERCA2, isoform of the SR Ca2+pump.

Modulation of vascular smooth muscle cell migration by calcium/ calmodulin-dependent protein kinase II-delta 2

Previous studies demonstrated a requirement for multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in PDGF-stimulated vascular smooth muscle (VSM) cell migration. In the present study, molecular approaches were used specifically to assess the role of the predominant CaMKII isoform (delta(2) or delta(C)) on VSM cell migration. Kinase-negative (K43A) and constitutively active (T287D) mutant forms of CaMKII delta(2) were expressed using recombinant adenoviruses. CaMKII activities were evaluated in vitro by using a peptide substrate and in intact cells by assessing the phosphorylation of overexpressed phospholamban on Thr(17), a CaMKII-selective phosphorylation site. Expression of kinase-negative CaMKII delta(2) inhibited substrate phosphorylation both in vitro and in the intact cell, indicating a dominant-negative function with respect to exogenous substrate. However, overexpression of the kinase-negative mutant failed to inhibit endogenous CaMKII delta(2) autophosphorylation on Thr(287) after activation of cells with ionomycin, and in fact, these subunits served as a substrate for the endogenous kinase. Constitutively active CaMKII delta(2) phosphorylated substrate in vitro without added Ca(2+)/calmodulin and in the intact cell without added Ca(2+)-dependent stimuli, but it inhibited autophosphorylation of endogenous CaMKII delta(2) on Thr(287). Basal and PDGF-stimulated cell migration was significantly enhanced in cells expressing kinase-negative CaMKII delta(2), an effect opposite that of KN-93, a chemical inhibitor of CaMKII activation. Expression of the constitutively active CaMKII delta(2) mutant inhibited PDGF-stimulated cell migration. These studies point to a role for the CaMKII delta(2) isoform in regulating VSM cell migration. An inclusive interpretation of results using both pharmacological and molecular approaches raises the hypothesis that CaMKII delta(2) autophosphorylation may play an important role in PDGF-stimulated VSM cell migration.