Mutations of ventricular essential myosin light chain disturb myosin binding and sarcomeric sorting

摘要

Aims: We tested the hypothesis that mutations in the human ventricular essential myosin light chain (hVLC-1) that are associated with hypertrophic cardiomyopathy (HCM) affect protein structure, binding to the IQ1 motif of cardiac myosin heavy chain (MYH) and sarcomeric sorting in neonatal cardiomyocytes. Methods and results: We employed circular dichroism and surface plasmon resonance spectroscopy to investigate structural properties and proteinprotein interactions of a recombinant head-rod fragment of rat cardiac β-MYH (amino acids 664915) with alanine-mutated IQ2 domain (rβ-MYH 664-915IQ2 ala4) and normal or five mutated (M149V, E143K, A57G, E56G, R154H) hVLC-1 forms. Double epitope-tagging competition was used to monitor the intracellular localization of exogenously introduced normal and E56G-mutated (hVLC-1 E56G) hVLC-1 constructs in neonatal rat cardiomyocytes. Fluorescence lifetime imaging microscopy was applied to map the microenvironment of normal and E56G-mutated hVLC-1 in permeabilized muscle fibres. Affinity of M149V, E143K, A57G, and R154H mutated hVLC-1/rβ-MYH 664-915IQ2 ala4 complexes was significantly lower compared with the normal hVLC-1/rβ-MYH 664-915IQ2 ala4 complex interaction. In particular, the E56G mutation induced an ～30-fold lower MYH affinity. Sorting specificity of E56G-mutated hVLC-1 was negligible compared with normal hVLC-1. Fluorescence lifetime of fibres replaced with hVLC-1 E56G increased significantly compared with hVLC-1-replaced fibres. Conclusion: Disturbed myosin binding of mutated hVLC-1 may provide a pathomechanism for the development of HCM.