Impaired functional communication between the L-type calcium channel and mitochondria contributes to metabolic inhibition in the mdx heart

Abstract

Duchenne muscular dystrophy is a fatal X-linked disease characterized by the absence of dystrophin. Approximately 20% of boys will die of dilated cardiomyopathy that is associated with cytoskeletal protein disarray, contractile dysfunction, and reduced energy production. However, the mechanisms for altered energy metabolism are not yet fully clarified. Calcium influx through the L-type Ca 2+ channel is critical for maintaining cardiac excitation and contraction. The L-type Ca 2+ channel also regulates mitochondrial function and metabolic activity via transmission of movement of the auxiliary beta subunit through intermediate filament proteins. Here, we find that activation of the L-type Ca 2+ channel is unable to induce increases in mitochondrial membrane potential and metabolic activity in intact cardiac myocytes from the murine model of Duchenne muscular dystrophy (mdx) despite robust increases recorded in wt myocytes. Treatment of mdx mice with morpholino oligomers to induce exon skipping of dystrophin exon 23 (that results in functional dystrophin accumulation) or application of a peptide that resulted in block of voltage-dependent anion channel (VDAC) "rescued" mitochondrial membrane potential and metabolic activity in mdx myocytes. The mitochondrial VDAC coimmunoprecipitated with the L-type Ca 2+ channel. We conclude that the absence of dystrophin in the mdx ventricular myocyte leads to impaired functional communication between the L-type Ca 2+ channel and mitochondrial VDAC. This appears to contribute to metabolic inhibition. These findings provide new mechanistic and functional insight into cardiomyopathy associated with Duchenne muscular dystrophy.ion channels | structure | cytoskeleton D uchenne muscular dystrophy affects 1:3,500 males, and in addition to skeletal muscle damage and atrophy, boys also develop a dilated cardiomyopathy due to the absence of expression of dystrophin. This pathology involves myocyte remodelling, disorganization of cytoskeletal proteins, and contractile dysfunction (1, 2). Early metabolic and signaling alterations have been reported in 10-to 12-wk-old murine model of Duchenne muscular dystrophy (mdx) hearts before the development of overt contractile dysfunction (2). However, the mechanisms by which absence of dystrophin leads to mitochondrial dysfunction and compromised cardiac function in mdx hearts are not fully clarified yet.Cytoskeletal proteins stabilize cell structure. In mature muscle, intermediate filaments form a 3D scaffold that extend from the Z disks to the plasma membrane and traverse cellular organelles such as t-tubules, sarcoplasmic reticulum, and mitochondria (3). Intermediate filaments and microtubules interact directly with mitochondria by binding to outer mitochondrial membrane proteins. In addition to a physical association, cytoskeletal proteins also regulate the function of proteins in the plasma membrane and within the cell (4). The L-type Ca 2+ channel (I Ca-L ) or dihydropyridine receptor (DHPR) is anchored to F-actin networks by subsarcolemmal sta...

The L‐type Ca2+ channel facilitates abnormal metabolic activity in the cTnI‐G203S mouse model of hypertrophic cardiomyopathy

“…; Viola et al . , ). Mouse hearts were excised, cannulated onto a Langendorff apparatus via the aorta and perfused with Krebs–Henseleit buffer containing (m m ): 120 NaCl, 25 NaHCO 3 , 4.8 KCl, 2.2 MgSO 4 , 1.2 NaH 2 PO 4 and 11 glucose (pH adjusted to 7.35 with 95% O 2 – 5% CO 2 at 37°C) for 4 min at 37°C.…”

Transverse tubule remodelling: a cellular pathology driven by both sides of the plasmalemma?

“…Potentially, the increased dilation of ttubules on the order of ∼150 nm could lead to structural remodelling of the cellular cytoskeleton, leading to the displacement of LTTC and RyR in cardiac junctions on the order of 10-20 nm required to disrupt Ca 2+ release. Consistent with this proposal, the MDX mouse that has no dystrophin has disrupted cellular cytoskeleton (Viola et al 2014) and disrupted calcium release (Cheng et al 2012). In addition, the vinculin-talin-integrin system could likely have a role in t-tubule remodelling, given its linkage to the actin cytoskeleton (Ziegler et al 2008) and the promiscuity of integrin (depending on the receptor sub-type) to bind to different ECM components, including laminin, fibronectin and collagens, including types I, III, IV and VI (Ross and Borg 2001;Tulla et al 2001), which have all been shown to be within the t-tubules (Kostin et al 1998;Crossman et al 2017).…”

“…In addition, the protein biglycan can bind to both collagen VI and the DGC (Wiberg et al 2001(Wiberg et al , 2002Rafii et al 2006). Dystrophin connects the sarcolemma to cellular cytoskeleton components, including actin filaments and microtubules (Renley et al 1998;Prins et al 2009), which, in turn, link to the L-type Ca 2+ channel (Viola et al 2014). Furthermore, microtubules have been implicated in trafficking both LTTC and RyR to cardiac junctions (Hong et al 2010;Zhang et al 2014).…”

The Mitochondrial Voltage-Dependent Anion Channel 1, Ca2+ Transport, Apoptosis, and Their Regulation

“…VDAC1 interacts with endothelial NO synthase (eNOS), with such interaction amplifying eNOS activity in a [Ca 2+ ] i -mediated manner (59). VDAC also interacts with the L-type Ca 2+ channel, and it was suggested that impaired communication between the L-type Ca 2+ channel and mitochondrial VDAC contributes to cardiomyopathy (60). Thus, such interactions of VDAC with proteins associated with Ca 2+ transport or activated by Ca 2+ point to VDAC as functioning not only in [Ca 2+ ] i homeostasis but also in many Ca 2+ -regulated cellular activities.…”