Dysferlin links excitation–contraction coupling to structure and maintenance of the cardiac transverse–axial tubule system

Abstract

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Aims</jats:title> <jats:p>The multi-C2 domain protein dysferlin localizes to the T-Tubule system of skeletal and heart muscles. In skeletal muscle, dysferlin is known to play a role in membrane repair and in T-tubule biogenesis and maintenance. Dysferlin deficiency manifests as muscular dystrophy of proximal and distal muscles. Cardiomyopathies have been also reported, and some dysferlinopathy mouse models develop cardiac dysfunction under stress. Generally, the role and functional relevance of dysferlin in the heart is not clear. The aim of this study was to analyse the effect of dysferlin deficiency on the transverse–axial tubule system (TATS) structure and on Ca2+ homeostasis in the heart.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods and results</jats:title> <jats:p>We studied dysferlin localization in rat and mouse cardiomyocytes by immunofluorescence microscopy. In dysferlin-deficient ventricular mouse cardiomyocytes, we analysed the TATS by live staining and assessed Ca2+ handling by patch-clamp experiments and measurement of Ca2+ transients and Ca2+ sparks. We found increasing co-localization of dysferlin with the L-type Ca2+-channel during TATS development and show that dysferlin deficiency leads to pathological loss of transversal and increase in longitudinal elements (axialization). We detected reduced L-type Ca2+-current (ICa,L) in cardiomyocytes from dysferlin-deficient mice and increased frequency of spontaneous sarcoplasmic reticulum Ca2+ release events resulting in pro-arrhythmic contractions. Moreover, cardiomyocytes from dysferlin-deficient mice showed an impaired response to β-adrenergic receptor stimulation.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Dysferlin is required for TATS biogenesis and maintenance in the heart by controlling the ratio of transversal and axial membrane elements. Absence of dysferlin leads to defects in Ca2+ homeostasis which may contribute to contractile heart dysfunction in dysferlinopathy patients.</jats:p> </jats:sec>

Ptpn23 Controls Cardiac T-Tubule Patterning by Promoting the Assembly of Dystrophin-Glycoprotein Complex

“…Ptpn23 deletion results in a decrease in transverse T-tubules and an increase in longitudinal T-tubules, which is similar to that observed in dysferlin knockout cardiomyocytes. 16 Because both Ptpn23 and dysferlin are involved in membrane remodeling, the similarity in T-tubule patterning after their disruption may reflect a defect in general membrane remodeling, which remains to be determined.…”

“…[1][2][3][4][5][6][7] A variety of membrane scaffolding proteins are involved in T-tubule biogenesis and maintenance, 2,8 including Bin1 (bridging integrator 1), 9 Jph2 (junctophilin-2), [10][11][12][13] nexilin, 14 Cav3 (caveolin 3), 15 and dysferlin. 16 However, it remains unclear how the organized T-tubules are formed along the Z-discs in cardiomyocytes.…”

On the role of dysferlin in striated muscle: membrane repair, t‐tubules and Ca2+ handling

“…The mechanisms that drive cardiac t‐tubule remodelling are not properly understood. However, recent evidence indicates that dysferlin associates with cardiac t‐tubules (Hofhuis et al., 2020), suggesting a similar relationship between dysferlin and the t‐tubule network may exist in both striated muscle types. Whilst there is a lack of evidence for cardiac sarcolemmal damage under physiological conditions, damage to the sarcolemma has been observed in specific cardiomyopathies (Clarke et al., 1995; Kostin et al., 2003).…”

“…Cardiomyopathy is usually absent or mild in dysferlin‐null animals, at least in young individuals under laboratory conditions (Chase et al., 2009; Hofhuis et al., 2020; Wei et al., 2015; Wenzel et al., 2007). Most reports show little to no evidence of cardiac hypertrophy or contractility in hearts or isolated cardiac myocytes from young dysferlin‐deficient mice compared to controls (Chase et al., 2009; Hofhuis et al., 2020; Wei et al., 2015; Wenzel et al., 2007).…”

Poster Session A

“…Dysferlin is a membrane repair protein that can generate tubules, de novo, in non-cardiac cell lines(Hofhuis et al, 2017) and is known to regulate t-tubules and EC coupling in skeletal myocytes(Klinge et al, 2007;Kerr et al, 2013). It is now emerging that dysferlin may regulate t-tubules and Ca 2+ handling in the heart(Hofhuis et al, 2020), but these mechanisms are poorly understood. Aims I)To investigate whether dysferlin regulates the structure of the mouse cardiac t-tubule network and whether dysferlin can prevent t-tubules from acute damage.…”