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Viola 2016 J Physiol

From Bioblast
Publications in the MiPMap
Viola H, Johnstone V, Szappanos HC, Richman T, Tsoutsman T, Filipovska A, Semsarian C, Hool L (2016) The L-type Ca2+ channel facilitates abnormal metabolic activity in the cTnI-G203S mouse model of hypertrophic cardiomyopathy. J Physiol 594:4051-70.

» PMID: 27062056 Open Access

Viola H, Johnstone V, Szappanos HC, Richman T, Tsoutsman T, Filipovska A, Semsarian C, Hool L (2016) J Physiol

Abstract: KEY POINTS: Genetic mutations in cardiac troponin I (cTnI) are associated with development of hypertrophic cardiomyopathy characterised by myocyte remodeling, disorganisation of cytoskeletal proteins and altered energy metabolism. The L-type Ca2+ channel is the main route for calcium influx and critical to cardiac excitation and contraction. The channel also regulates mitochondrial function in the heart by a functional communication between the channel and mitochondria via the cytoskeletal network. We find that L-type Ca2+ channel kinetics are altered in cTnI-G203S cardiac myocytes, and that activation of the channel causes a significantly greater increase in mitochondrial membrane potential and metabolic activity in cTnI-G203S cardiac myocytes. These responses occur as a result of impaired communication between the L-type Ca2+ channel and cytoskeletal protein F-actin, involving decreased movement of actin-myosin, and block of mitochondrial VDAC, resulting in a 'hypermetabolic' mitochondrial state. We propose that L-type Ca2+ channel antagonists such as diltiazem may be effective in reducing the cardiomyopathy by normalising mitochondrial metabolic activity.


ABSTRACT: Genetic mutations in cardiac troponin I (cTnI) account for 5% of families with hypertrophic cardiomyopathy (HCM). HCM is associated with disorganisation of cytoskeletal proteins and altered energy metabolism. The L-type Ca2+ channel (ICa-L ) plays an important role in regulating mitochondrial function. This involves a functional communication between ICa-L and mitochondria via the cytoskeletal network. We investigate the role of ICa-L in regulating mitochondrial function in 25-30-week old cardiomyopathic mice expressing human disease causing mutation Gly203Ser in cTnI (cTnI-G203S). The inactivation rate of ICa-L is significantly faster in cTnI-G203S myocytes (cTnI-G203S: τ1 = 40.68 ± 3.22, n = 10 versus wt: τ1 = 59.05 ± 6.40, n = 6, P < 0.05). Activation of ICa-L caused a greater increase in mitochondrial membrane potential (Ψm , 29.19 ± 1.85%, n = 15 versus wt: 18.84 ± 2.01%, n = 10, P < 0.05) and metabolic activity (24.40 ± 6.46%, n = 8 versus wt: 9.98 ± 1.57%, n = 9, P < 0.05). The responses occurred due to impaired communication between ICa-L and F-actin, involving lack of dynamic movement of actin-myosin, and block of mitochondrial VDAC. Similar responses were observed in pre-cardiomyopathic mice. ICa-L antagonists nisoldipine and diltiazem decreased Ψm to basal levels. We conclude that the Gly203Ser mutation leads to impaired functional communication between ICa-L and mitochondria resulting in a 'hypermetabolic' state. This may contribute to development of cTnI-G203S cardiomyopathy because the response is present in young pre-cardiomyopathic mice. ICa-L antagonists may be effective in reducing the cardiomyopathy by altering mitochondrial function. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved. Keywords: L-type Ca2+ channel, Mitochondria, Metabolism, Cardiomyopathy

O2k-Network Lab: AU Perth Filipovska A


Labels: MiParea: Respiration  Pathology: Cardiovascular, Myopathy 

Organism: Mouse  Tissue;cell: Heart  Preparation: Isolated mitochondria 


Pathway: N, S, CIV  HRR: Oxygraph-2k 

2016-06