Biased signaling of Ca2+-sensing receptors in cardiac myocytes regulates GIRK channel activity

ABSTRACTBackgroundDrug-induced neuroadaptations in the prefrontal cortex are thought to underlie impaired executive functions that reinforce addictive behaviors. Repeated cocaine exposure increased layer 5/6 pyramidal neuron excitability in the mouse prelimbic cortex (PL), an adaptation attributable to a suppression of G protein-gated inwardly rectifying K+ (GIRK/Kir3) channel activity. GIRK channel suppression in the PL of drug-naïve mice enhanced the motor-stimulatory effect of cocaine. The impact of cocaine on PL GABA neurons, key pyramidal neuron regulators, and the behavioral relevance of increased PL pyramidal neuron excitability, remain unclear.MethodsThe effect of repeated cocaine on mouse layer 5/6 PL GABA neurons was assessed using slice electrophysiology. Adaptations enhancing PL pyramidal neuron excitability were modeled in drug-naïve mice using persistent viral Cre ablation and acute chemogenetic approaches. The impact of these manipulations on PL-dependent behavior was assessed in motor activity and trace fear conditioning tests.ResultsRepeated cocaine treatment did not impact GIRK channel activity in, or excitability of, layer 5/6 PL GABA neurons. GIRK channel ablation in PL pyramidal neurons enhanced the motor-stimulatory effect of cocaine but did not impact baseline activity or fear learning. In contrast, direct or indirect chemogenetic activation of PL pyramidal neurons increased baseline and cocaine-induced motor activity and disrupted fear learning. These effects were mirrored by chemogenetic activation of PL pyramidal neurons projecting to the ventral tegmental area.ConclusionsManipulations enhancing the excitability of PL pyramidal neurons, including those projecting to the VTA, recapitulate behavioral hallmarks of repeated cocaine exposure.

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Abstract 078: Differential Phosphorylation of Inositol 1,4,5-triphophate Receptor by CaMKIId During Cardiac Remodeling

Circulation Research ◽

10.1161/res.113.suppl_1.a078 ◽

2013 ◽

Vol 113 (suppl_1) ◽

Author(s):

Natesan Sankar

Keyword(s):

Cardiac Myocytes ◽

Cardiac Remodeling ◽

Pressure Overload ◽

University Of California ◽

Medical Institute ◽

Channel Activity ◽

Molecular Physiology ◽

Human Heart Failure ◽

Release Channel ◽

Differential Phosphorylation

Natesan Sankar 1 , Sukriti Dewan 1 , Joshua Maxwell 1 , Donald Bers 2 , Joan Heller Brown 3 , Jeffery Molkentin 4 , Pieter deTombe 1 , Gregory Mignery 1 . 1 Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL. 2 Department of Physiology, Department of Pharmacology University of California at Davis, Davis, CA. 3 Department of Pharmacology, University of California, San Diego, La Jolla, CA. 4 Howard Hughes Medical Institute, Molecular Cardiovascular Biology, Cincinnati Children’s Hospital, Cincinnati, OH. In cardiac myocytes the type-2 isoform of the inositol 1,4,5-triphosphate receptor (InsP 3 R2) Ca 2+ release channel is expressed predominantly in the nuclear envelope. InsP 3 R2 releases intracellular Ca 2+ bidirectionally towards the cytoplasm and nucleoplasm in response to an array of pro-hypertrophic signaling. Thus, InsP 3 R2 mediated Ca 2+ release may contribute to both Excitation-Contraction Coupling (ECC) and Excitation-Transcription Coupling (ETC) during normal and pathophysiologic conditions such as cardiac remodeling. However, the regulation of InsP 3 R2 mediated Ca 2+ release and its role in ECC and ETC during cardiac remodeling is not fully understood. We have shown that CaMKIIδ and InsP 3 R2 forms a signaling complex in the heart and CaMKII mediated phosphorylation of InsP 3 R2 at S150 modulates its intrinsic Ca 2+ channel activity. Here we show that InsP 3 R2 is differentially phosphorylated by CaMKIIδ B and CaMKIIδ C , the predominant nucleoplasmic and cytoplasmic isoforms respectively, in cardiac myocytes. Using adult rat cardiac myocytes we show that the differential phosphorylation by CaMKII of InsP 3 R2 at S150 leads to elevated nuclear Ca 2+ signaling and diminished release towards the cytoplasm. Additionally we show that the InsP 3 R2 was phosphorylated in the hearts of Angiotensin II infused and pressure overload induced cardiac remodeling animal models. Finally, we show that there was an increase in InsP 3 R2 phosphorylation in human heart-failure samples compared to non-failing hearts. Collectively our studies demonstrate that, CaMKIIδ mediated regulation of InsP 3 R2 Ca 2+ channel activity contributes to ECC and ETC during all the phases of cardiac remodeling processes.

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Detection of Acute Hypoxia in Cardiac Myocytes using Calcium Channel Activity and O2-Sensitive Coverslips

Biophysical Journal ◽

10.1016/j.bpj.2012.11.2544 ◽

2013 ◽

Vol 104 (2) ◽

pp. 460a

Author(s):

John A. Scaringi ◽

Angelo O. Rosa ◽

Lars Cleemann ◽

Martin Morad

Keyword(s):

Calcium Channel ◽

Cardiac Myocytes ◽

Acute Hypoxia ◽

Channel Activity

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High Cholesterol Diet Up-Regulates Atrial and Neuronal GIRK Channel Activity

Biophysical Journal ◽

10.1016/j.bpj.2018.11.1228 ◽

2019 ◽

Vol 116 (3) ◽

pp. 223a

Author(s):

Anna N. Bukiya ◽

Avia Rosenhouse-Dantsker

Keyword(s):

High Cholesterol Diet ◽

Cholesterol Diet ◽

Channel Activity ◽

High Cholesterol ◽

Girk Channel

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Abstract 298: CaMKII-Mediated Phosphorylation of InsP3R2 Activates Hypertrophic Gene Transcription

Circulation Research ◽

10.1161/res.111.suppl_1.a298 ◽

2012 ◽

Vol 111 (suppl_1) ◽

Author(s):

Sankar Natesan ◽

Joshua T Maxwell ◽

Paul R Hale ◽

Gregory A Mignery

Keyword(s):

Gene Expression ◽

Cardiac Hypertrophy ◽

Cardiac Myocytes ◽

Gene Transcription ◽

Underlying Mechanism ◽

Channel Activity ◽

Endothelin 1 ◽

Insp3 Receptors ◽

Hypertrophic Signaling ◽

Ca2 Channels

Inositol 1,4,5-triphosphosphate receptors are a family of intracellular Ca2+ channels, modulated by the ligands InsP3 and Ca2+ in response to an array of neuro-hormonal stimuli to release Ca2+ from internal stores. In cardiac myocytes, the InsP3R2, CaMKII and CaM are components of a macromolecular signalplex. However, modulation of InsP3R’s Ca2+ channel and the underlying mechanism(s) that converge and integrate nuclear hypertrophic signals to initiate transcription is not fully established. Here, we delineate the mechanistic regulation of nuclear InsP3R2’s bidirectional Ca2+ channel activity and its effect on the activation of nuclear hypertrophic signaling. We show that, endothelin-1 (ET1) stimulates elevated InsP3 induced Ca2+ release into the nucleus from perinuclear InsP3 receptors. This elevated nuclear Ca2+ release is due to CaMKIIδ mediated phosphorylation of cytoplasmic oriented InsP3R2 inhibiting Ca2+ release to the cytoplasm. This increase in nuclear Ca2+ activates Ca2+ sensitive transctiption factors thereby activating gene expression. The elevated nuclear Ca2+ and gene expression can be attenuated by CaMKII inhibitor KN-93 and InsP3R antagonist 2-ABP. We also show that, exogenous InsP3R2 was phosphorylated by both cytoplasmic (CaMKIIδC) and nuclear (CaMKIIδB) isoforms of CaMKIIδ. Intriguingly, CaMKIIδC phosphorylates endogenous InsP3R2 in cardiomyocytes more efficiently than CaMKIIδB and not by its kinase-dead derivatives. In conclusion, our findings demonstrate that, InsP3R2 mediated Ca2+ signaling integrates and vectors the GPCR activated hypertrophic signals to the nucleus triggering gene transcription underlying cardiac hypertrophy.

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