An In Silico Analysis of Troponin I Mutations in Hypertrophic Cardiomyopathy of Indian Origin

Abstract

Hypertrophic Cardiomyopathy (HCM) is an autosomal dominant disorder of the myocardium which is hypertrophied resulting in arrhythmias and heart failure leading to sudden cardiac death (SCD). Several sarcomeric proteins and modifier genes have been implicated in this disease. Troponin I, being a part of the Troponin complex (troponin I, troponin C, troponin T), is an important gene for sarcomeric function. Four mutations (1 novel) were identified in Indian HCM cases, namely, Pro82Ser, Arg98Gln, Arg141Gln and Arg162Gln in Troponin I protein, which are in functionally significant domains. In order to analyse the effect of the mutations on protein stability and protein-protein interactions within the Troponin complex, an in silico study was carried out. The freely available X-ray crystal structure (PDB ID: 1JIE) was used as the template to model the protein followed by loop generation and development of troponin complex for both the troponin I wild type and four mutants (NCBI ID: PRJNA194382). The structural study was carried out to determine the effect of mutation on the structural stability and protein-protein interactions between three subunits in the complex. These mutations, especially the arginine to glutamine substitutions were found to result in local perturbations within the troponin complex by creating/removing inter/intra molecular hydrogen bonds with troponin T and troponin C. This has led to a decrease in the protein stability and loss of important interactions between the three subunits. It could have a significant impact on the disease progression when coupled with allelic heterogeneity which was observed in the cases carrying these mutations. However, this can be further confirmed by functional studies on protein levels in the identified cases.

Cardiac troponin I Pro82Ser variant induces diastolic dysfunction, blunts β-adrenergic response, and impairs myofilament cooperativity

“…6A). Similarly, the model of TnIPro82Ser of Ramachandran and colleagues (37) pointed out that serine substitution might result in a hydrogen bond interaction with the butyl ammonium nitrogen of Lys234 in TnT and perturb TnI-TnT interactions. Thus TnIPro82Ser appear to have similar structural and phenotypic effects as the dominant negative mutation in TnI Cys111Arg, which also decrease the binding affinity of TnI for TnT.…”

Identification of novel L2HGDH mutation in a large consanguineous Pakistani family- a case report

“…The mutation was predicted to affect the hydrogen bonding, and thus alter the stereochemistry of the protein (Fig. 3 ) [ 22 ].…”

A Complete Absence of Missense Mutation in Myosin Regulatory and Essential Light Chain Genes of South Indian Hypertrophic and Dilated Cardiomyopathies

“…Many of the studies on these genes have been carried out in other countries; however, very little data are available in India. Our previous studies on myosin binding protein C ( MyBPC3 ) [7], RAF1 [8], troponin I3 ( TNNI3 ) [9, 10], troponin T2 ( TNNT2 ) [11, 12], and actin ( ACTC ) [14], using the same set of samples (partly/fully), have revealed a few pathogenic mutations [9-16]. The mutations in myosin regulatory ( MYL2) and essential ( MYL3) light chains are reported to be associated with cardiomyopathies, however, there is no study available on these genes in Indian cardiomyopathies, and therefore we studied them.…”

“…Thus, the etiology of disease due to myosin light-chain genes has remained not understood in Indian cardiomyopathy patients. Previously, we have reported a few mutations and the associations with Indian cardiomyopathies in the following genes: myosin binding protein C ( MyBPC3 ) [7], RAF1 [8], troponin I3 ( TNNI3 ) [9, 10], troponin T2 ( TNNT2 ) [11, 12], tropomyosin ( TPM1) [13], actin ( ACTC ) [14], and cardiac β-myosin heavy chains ( β-MYH7 ), and we also submitted these novel mutations to the dbSNP data bank (https://www.ncbi.nlm.nih.gov/projects/SNP/snp_viewBatch.cgi?sbid = 1062022). In the present study we have screened the myosin regulatory ( MYL2) and essential ( MYL3) light-chain genes to establish their role among Indian cardiomyopathies, using the same set of samples (partly/fully), which were used for the above mutational studies [9-16].…”