Peptidomimetic Targeting of Ca _v β2 Overcomes Dysregulation of the L-Type Calcium Channel Density and Recovers Cardiac Function

Abstract

Original research article BACKGROUND: L-type calcium channels (LTCCs) play important roles in regulating cardiomyocyte physiology, which is governed by appropriate LTCC trafficking to and density at the cell surface. Factors influencing the expression, half-life, subcellular trafficking, and gating of LTCCs are therefore critically involved in conditions of cardiac physiology and disease. METHODS:Yeast 2-hybrid screenings, biochemical and molecular evaluations, protein interaction assays, fluorescence microscopy, structural molecular modeling, and functional studies were used to investigate the molecular mechanisms through which the LTCC Ca v β2 chaperone regulates channel density at the plasma membrane. RESULTS:On the basis of our previous results, we found a direct linear correlation between the total amount of the LTCC pore-forming Ca v α1.2 and the Akt-dependent phosphorylation status of Ca v β2 both in a mouse model of diabetic cardiac disease and in 6 diabetic and 7 nondiabetic cardiomyopathy patients with aortic stenosis undergoing aortic valve replacement. Mechanistically, we demonstrate that a conformational change in Ca v β2 triggered by Akt phosphorylation increases LTCC density at the cardiac plasma membrane, and thus the inward calcium current, through a complex pathway involving reduction of Ca v α1.2 retrograde trafficking and protein degradation through the prevention of dynaminmediated LTCC endocytosis; promotion of Ca v α1.2 anterograde trafficking by blocking Kir/Gem-dependent sequestration of Ca v β2, thus facilitating the chaperoning of Ca v α1.2; and promotion of Ca v α1.2 transcription by the prevention of Kir/Gem-mediated shuttling of Ca v β2 to the nucleus, where it limits the transcription of Ca v α1.2 through recruitment of the heterochromatin protein 1γ epigenetic repressor to the Cacna1c promoter. On the basis of this mechanism, we developed a novel mimetic peptide that, through targeting of Ca v β2, corrects LTCC lifecycle alterations, facilitating the proper function of cardiac cells. Delivery of mimetic peptide into a mouse model of diabetic cardiac disease associated with LTCC abnormalities restored impaired calcium balance and recovered cardiac function. CONCLUSIONS:We have uncovered novel mechanisms modulating LTCC trafficking and life cycle and provide proof of concept for the use of Ca v β2 mimetic peptide as a novel therapeutic tool for the improvement of cardiac conditions correlated with alterations in LTCC levels and function.Peptidomimetic targeting of ca v β2 Overcomes Dysregulation of the l-type calcium channel Density and recovers cardiac Function

Inhalation of peptide-loaded nanoparticles improves heart failure

“…3B and table S4). Improvement of molecular and cellular defects associated with diabetic cardiomyopathy was achieved as a result of the direct targeting of MP to LTCC (24), including restoration of LTCC protein levels ( Fig. 3C and fig.…”

“…All animals were obtained from the Charles River Laboratories. Therapeutic treatment of mice was performed as follows: Type 1 diabetes was induced in adult C57B6/J male mice by intraperitoneal injection of STZ (50 mg/kg per day) for five consecutive days as previously described (24). Seven days after the last STZ injection, whole blood was obtained from the mouse tail vein and glucose levels were measured using the Accu-Chek Aviva blood glucose monitoring system (Roche).…”

“…A Vevo 2100 high-resolution in vivo imaging system (VisualSonics Fujifilm) with a MS550S probe "high frame" scan head was used for echocardiographic analysis. Mice were anesthetized with 1.0% isoflurane and imaged in M-mode as previously described (24).…”

Partners in Crime: Towards New Ways of Targeting Calcium Channels

“…Interestingly, in a number of cardiac pathologies, there is a decreased expression of CaV1.2 VDCC [29]. A recent study has demonstrated that the physiological expression of CaV1.2 at the plasma membrane depends on Akt-dependent phosphorylation of β2 at its C-terminus, allowing binding of β2 with CaV1.2 [30]. Another actor, Kir/Gem, also regulates the association between CaV1.2 and β subunits.…”

Diabetic Cardiomyopathy: Current Approach and Potential Diagnostic and Therapeutic Targets

“…Therefore, further studies addressing pharmacokinetic analysis are required; since supraphysiological levels of Ca v α 1.2 and Ca v β 2 exert detrimental effects regarding myocyte function, effects which are beyond the linear correlation between Ca v α 1.2 and Ca v β 2 are highlighted by preliminary data [47]. Moreover, several tissue-specific elements should be tackled; since Ca v β 2 has a broad tissue distribution, not being limited to cardiac tissue, thus possibly generating several issues, difficulty which might be overcome by using functionalized nanoparticles [47, 48] allow specific cardiac delivery.…”