β-Adrenergic Receptor Activation Induces Internalization of Cardiac Cav1.2 Channel Complexes through a β-Arrestin 1-mediated Pathway

Abstract

Voltage-dependent calcium channels (VDCCs) play a pivotal role in normal excitation-contraction coupling in cardiac myocytes. These channels can be modulated through activation of ␤-adrenergic receptors (␤-ARs), which leads to an increase in calcium current (I Ca-L ) density through cardiac Ca v 1 channels as a result of phosphorylation by cAMP-dependent protein kinase A. Changes in I Ca-L density and kinetics in heart failure often occur in the absence of changes in Ca v 1 channel expression, arguing for the importance of posttranslational modification of these channels in heart disease. The precise molecular mechanisms that govern the regulation of VDCCs and their cell surface localization remain unknown. Our data show that sustained ␤-AR activation induces internalization of a cardiac macromolecular complex involving VDCC and ␤-arrestin 1 (␤-Arr1) into clathrincoated vesicles. Pretreatment of myocytes with pertussis toxin prevents the internalization of VDCCs, suggesting that G i/o mediates this response. A peptide that selectively disrupts the interaction between Ca V 1.2 and ␤-Arr1 and tyrosine kinase inhibitors readily prevent agonist-induced VDCC internalization. These observations suggest that VDCC trafficking is mediated by G protein switching to G i of the ␤-AR, which plays a prominent role in various cardiac pathologies associated with a hyperadrenergic state, such as hypertrophy and heart failure. Regulation of voltage-dependent calcium channels (VDCCs)3 plays a pivotal role in excitation-contraction coupling in cardiac myocytes. During the action potential upstroke, membrane depolarization causes the opening of VDCCs, encoded by the pore-forming ␣ 1 subunit, Ca v 1.2 (1). Ca 2ϩ entry through VDCCs triggers the release of Ca 2ϩ from the sarcoplasmic reticulum via ryanodine receptors. Although the regulation of VDCCs in the heart has been extensively studied, key molecular mechanisms underlying channel function, trafficking, membrane targeting, retention, and internalization remain unknown. Activation of the ␤-AR, a G protein-coupled receptor (GPCR), leads to positive inotropic effects mediated by phosphorylation of the VDCC via cAMP-dependent protein kinase A (2). This, however, is a transient phenomenon since persistent activation of the receptor causes its subsequent phosphorylation by GPCR kinases (GRKs) (3), causing the ␤-AR to become a target for arrestin (4), which mediates the recruitment of the receptor into clathrin-coated vesicles (5).In addition to decreasing single channel permeability, persistent membrane depolarization can regulate the number of Ca v 1.2 channels at the plasma membrane. For example, sustained KCl-induced depolarization of rat cortical neurons effectively decreases Ca v 1.2 channel activity (6). Ca v 1.2 channels have been proposed to contain a membrane-targeting domain within their calmodulin (CaM)-binding domain in the C terminus (7). Pitt and colleagues (8) showed that Ca 2ϩ -CaM interaction with this domain accelerated the rate of trafficking of Ca v 1.2 channels to ...

Heterodimerization of ORL1 and Opioid Receptors and Its Consequences for N-type Calcium Channel Regulation

“…This indicates the presence of ORL1/-opioid receptor/ N-type channel complexes and suggests that the ORL1 receptors act as an intermediary, physically coupling the -opioid receptors to N-type channels. This receptor-induced channel internalization adds to an increasing body of evidence showing that various G protein-coupled receptors form signaling complexes with voltage-gated calcium channels and regulate their membrane expression (15,23,(31)(32)(33). It is possible that ␦-and -opioid receptors might mediate a similar trafficking effect, perhaps even in the absence of coexpressed ORL1 receptors, but this was not examined here and will be subject to further investigation.…”

β-arrestin-mediated receptor trafficking and signal transduction

“…Akin to the TGF-β III receptor, the Na + /H + exchanger NHE1 and NHE5 isoforms also internalize and are downregulated in a β-arrestin-dependent manner [68,69]. In addition, β-arrestins are key regulators of the ligand-gated ion channel nicotinic cholinergic receptor [70], cardiac Ca(v)1 voltage-gated channels [71] and the transient receptor potential (TRP) ion channel, TRPV4 [72] (see below).…”

Emerging paradigms of β-arrestin-dependent seven transmembrane receptor signaling

“…β-arrestins are critical for the internalization or ubiquitylation (or both) of the type III transforming growth factor β (TGF-β) receptor [31], the insulin-like growth factor I (IGF1) receptor [32], voltage-dependent calcium channels [33,34], transient receptor potential channel vanilloid type (TRPV4) [35], the Na(+)/H(+) exchanger 1 (NHE1) [36], the neuronal Na(+)/H(+) exchanger NHE5 [37], the androgen receptor [38] and the vascular endothelial (VE) cadherin [39]. Moreover, kurtz, the single nonvisual arrestin expressed in Drosophila , is critically involved in deltex-mediated Notch ubiquitylation and degradation [40].…”