Troponin T (TnT), the tropomyosin (Tm)-binding subunit of troponin complex, plays a central role in regulating cardiac muscle contractility. The newly characterized Tm-binding site 3 in the C-terminal end segment of TnT (PMID: 40591592) exhibits a troponin I (TnI)-like thin filament inhibitory function which is retained in the form of isolated 14 amino acids peptide (cTnT-C14) (PMID: 40672242). In hypertrophic cardiomyopathy (HCM), hypercontractility leads to impaired ventricular relaxation to restrict diastolic filling and cause heart failure with preserved ejection fraction (HFpEF). To develop a myocardial contractile kinetics-targeted treatment for HFpEF, we designed a heart-homing, membrane-penetrating cTnT-C14 fusion peptide and successfully expressed it in E. coli culture. Purified cTnT-C14 fusion peptide was delivered into freshly isolated adult mouse cardiomyocytes. Contractility studies showed that treatment with a low concentration (0.5 micromolar) of cTnT-C14 fusion peptide reduced contractile amplitude and notably shortened the twitch duration, increasing the time of diastole which can improve ventricular filling. The potency of functional effects demonstrates the efficacy of the fusion peptide approach for cardiomyocyte delivery whereas control treatment with the heart-homing and membrane-penetrating segment alone does not have significant effect on contractility. cTnT-C14 fusion peptide treatment of cardiomyocytes isolated from transgenic mice expressing an HCM mutation of cardiac tropomyosin (Tm-E180G) achieved a therapeutic effect on reducing contractile kinetics to correct the hypercontractile phenotype. The results provide proof-of-concept evidence that the cTnT-C14 fusion peptide can be readily delivered into cardiomyocytes as a therapeutic reagent with potent functional effects to attenuate hypercontractility and improve diastolic function. Studies in ex vivo working hearts and in vivo are underway to further establish the translational value of this myocardial kinetics-targeted novel treatment for HCM and other HFpEF conditions.
Li et al. (Sun,) studied this question.